Supporting Information. Ruthenium(II)-Catalyzed C H Alkynylation of Weakly-Coordinating Benzoic Acids. Ruhuai Mei, Shou-Kun Zhang, and Lutz Ackermann*

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1 Supporting Information Ruthenium(II)-Catalyzed C H Alkynylation of Weakly-Coordinating Benzoic Acids Ruhuai Mei, Shou-Kun Zhang, and Lutz Ackermann* Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Tammannstraße 2, Göttingen, Germany Fax: +49/ Lutz.Ackermann@chemie.uni-goettingen.de General Remarks S-1 Optimization studies S-2 General Procedures for the Ruthenium(II)-Catalyzed C H Alkynylation S-3 Characterization Data of Products 3 and 7 S-4 C H Alkynylation/Cyclization Cascade S-20 Mechanistic Studies S-21 Removal of Silyl Group S-25 Decarboxylative C H Alkynylation S-26 References S-28 1 H-, 13 C- and 19 F-NMR Spectra S-29 S-0

2 General Remarks Catalytic reactions were carried out in Schlenk tubes under a nitrogen atmosphere using predried glassware, 1,4-dioxane and toluene were dried with sodium and freshly distilled under N 2. N-Methyl-2-pyrrolidon (NMP) was dried and distilled over CaH 2. The following starting materials were synthesized according to previously described procedures: [Ru(O 2 CMes) 2 (pcymene)], [1] (bromoethynyl)triisopropylsilane 2a, [2] (bromoethynyl)(tert-butyl)dimethylsilane 2b. [2] Other chemicals were obtained from commercial sources and were used without further purification. Yields refer to isolated compounds, estimated to be > 95% pure as determined by 1 H-NMR and GC-analysis. Chromatography: Merck silica gel 60 (40-63 μm). NMR: Spectra were recorded on Varian Unity 300, Mercury 300 or Inova 500 in the solvent indicated; chemical shifts (δ) are given in ppm. All IR spectra were recorded on a Bruker FT-IR Alpha device. MS: EI-MS- and ESI-MS-spectra were recorded with Finnigan MAT 95, 70 ev; High resolution mass spectrometry (HR-MS) with APEX IV 7T FTICR, Bruker Daltonic. M. p.: Stuart melting point apparatus SMP3, Barloworld Scientific, values are uncorrected. Preparative separations were performed on preparative HPLC system from JAI (LC-92XX II Series) connected to JAIGEL HH series column. S-1

3 Table S-1 Optimization Study for Ruthenium (II)-Catalyzed C H Alkynylation a entry base solvent 3a (%) b 1 K 2 CO 3 NMP 63 2 NHCy 2 NMP 55 3 DBU NMP (47) 4 NaHCO 3 NMP 47 5 KOAc NMP (22) 6 K 3 PO 4 NMP 33 7 K 2 CO 3 NMP --- c 8 K 2 CO 3 NMP 46 d 9 K 2 CO 3 DMA (52) 10 K 2 CO 3 DMF K 2 CO 3 DMPU (57) 12 K 2 CO 3 GVL (47) 13 K 2 CO 3 CH 3 CN K 2 CO 3 PhMe K 2 CO 3 1,4-dioxane K 2 CO 3 1,4-dioxane 39 e 17 K 2 CO 3 1,4-dioxane 24 f 18 K 2 CO 3 1,4-dioxane 40 g a Reaction conditions: 1a (0.50 mmol), 2a (0.65 mmol), 4 (10 mol %), base (1.0 mmol), solvent (1.0 ml), 120 C, 16 h; then K 2 CO 3 (2.0 equiv) and MeI (5.0 equiv) in MeCN (3.0 ml), 55 C, 2 h. b Yields of isolated product; in parentheses: 1 H-NMR conversion upon esterification, using 1,3,5-trimethoxybezene as the internal standard. c [RuCl 2 (p-cymene)] 2 (5.0 mol %), AgSbF 6 (20 mol %). d X-phos (10 mol %) as additive. e Using the corresponding alkynyl chloride. f Using the corresponding iodide. g Performing the reaction at 100 C. S-2

4 General Procedures for the Ruthenium(II)-Catalyzed C H Alkynylation General Procedure for the C H Alkynylation of Benzoic Acids (GP1) A suspension of [Ru(O 2 CMes) 2 (p-cymene)] (4) (28.1 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol), benzoic acid 1 (0.50 mmol), and alkynyl bromide 2 (0.65 mmol, 1.30 equiv) in 1,4- dioxane (1.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, MeCN (3.0 ml), K 2 CO 3 (138 mg, 1.0 mmol) and MeI (355 mg, 2.50 mmol) were added and the mixture was stirred at 50 ºC for additional 2 h. At ambient temperature, the mixture was dryloaded onto silica gel and purified by was purified by column chromatography (nhexane/etoac) and HPLC (when required) to give products 3. General Procedure for the C H Alkynylation of Benzoic Acids: Access to Free Acids 7 (GP2) A suspension of [RuCl 2 (p-cymene)] 2 (15.3 mg, 5.0 mol %), K 2 CO 3 (138 mg, 1.00 mmol), benzoic acid 1 (0.50 mmol), and alkynyl bromide 2 (0.65 mmol, 1.30 equiv) in 1,4-dioxane (1.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, HOAc (2.0 ml) was added, the mixture was dry-loaded onto silica gel and purified by column chromatography (n-hexane/etoac/acoh) to give products 7. S-3

5 Characterization Data of Products 3 and 7 Methyl 3,4,6-trimethoxy-2-[(triisopropylsilyl)ethynyl]benzoate (3a) Representative procedure for the Ruthenium(II)-Catalyzed C H Alkynylation: A suspension of [Ru(O 2 CMes) 2 (p-cymene)] (4) (56.2 mg, 10 mol %), K 2 CO 3 (276 mg, 2.00 mmol), benzoic acid 1a (212.2 mg, 1.00 mmol), and alkynyl bromide 2a (339.7 mg, 1.30 mmol) in 1,4-dioxane (2.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, MeCN (6.0 ml), K 2 CO 3 (276 mg, 2.0 mmol) and MeI (710 mg, 5.00 mmol) were added and the mixture was stirred at 50 ºC for additional 2 h. At ambient temperature, the mixture was dry-loaded onto silica gel and purified by column chromatography (nhexane/etoac 2/1) to give product 3a (366.0 mg, 90%) as a colorless solid. When the reaction was running in 0.50 mmol scale, 88% yield was got. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 6.46 (s, 1H), 3.84 (s, 3H), 3.84 (s, 3H), 3.80 (s, 3H), 3.78 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), (C q ), 99.5 (C q ), 99.1 (C q ), 98.2 (CH), 61.0 (CH 3 ), 56.6 (CH 3 ), 56.1 (CH 3 ), 52.3 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2942, 2864, 2157, 1734, 1585, 1267, 881, 674 cm -1. MS (ESI) m/z (relative intensity) 429 (10) [M+Na + ], 407 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 22 H 35 O 5 Si [M+H + ] , found S-4

6 Methyl 2,4-dimethoxy-6-[(triisopropylsilyl)ethynyl]benzoate (3b) The general procedure GP1 was followed using benzoic acid 1b (91 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 5:1) yielded 3b (143 mg, 76%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 6.55 (d, J = 2.2 Hz, 1H), 6.41 (d, J = 2.2 Hz, 1H), 3.83 (s, 3H), 3.77 (s, 3H), 3.76 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), (CH), (C q ), 99.6 (CH), 94.4 (C q ), 55.9 (CH 3 ), 55.5 (CH 3 ), 52.2 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2943, 2865, 2150, 1732, 1574, 1267, 1156, 881, 674 cm -1. MS (ESI) m/z (relative intensity) 399 (20) [M+Na + ], 377 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 21 H 33 O 4 Si [M+H + ] , found Methyl 3,6-dimethyl-2-[(triisopropylsilyl)ethynyl]benzoate (3c) The general procedure GP1 was followed using benzoic acid 1c (75 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 4:1) and then by HPLC yielded 3c (129 mg, 75%) as a pale yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.11 (d, J = 7.9 Hz, 1H), 7.02 (d, J = 7.9 Hz, 1H), 3.88 (s, 3H), 2.41 (s, 3H), 2.24 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (CH), (C q ), (C q ), 98.7 (C q ), 52.2 (CH 3 ), 20.6 (CH 3 ), 18.9 (CH 3 ), 18.6 (CH 3 ), 11.2 (CH). IR (neat): 2943, 2864, 2150, 1734, 1273, 1136, 882, 757, 672 cm -1. MS (ESI) m/z (relative intensity) 367 (10) [M+Na + ], 345 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 21 H 33 O 2 Si [M+H + ] , found S-5

7 Methyl 2,3-dimethoxy-6-[(triisopropylsilyl)ethynyl]benzoate (3d) The general procedure GP1 was followed using benzoic acid 1d (91 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 10:1) yielded 3d (154 mg, 82%) as a colorless solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.19 (d, J = 8.6 Hz, 1H), 6.82 (d, J = 8.6 Hz, 1H), 3.87 (s, 3H), 3.83 (s, 3H), 3.81 (s, 3H), (m, 21H). 13 C NMR (125 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (C q ), (CH), (C q ), 92.5 (C q ), 61.5 (CH 3 ), 55.9 (CH 3 ), 52.4 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2942, 2863, 2149, 1731, 1463, 1272, 1048, 826, 660 cm -1. MS (ESI) m/z (relative intensity) 399 (20) [M+Na + ], 377 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 21 H 33 O 4 Si [M+H + ] , found Methyl 6-[(tert-butyldimethylsilyl)ethynyl]-2,3-dimethoxybenzoate (3e) A suspension of [Ru(O 2 CMes) 2 (p-cymene)] (4) (28.1 mg, 10 mol %), K 2 CO 3 (69 mg, 0.50 mmol), benzoic acid 1d (91 mg, 0.50 mmol) and (bromoethynyl)(tert-butyl)dimethylsilane (2b) (219 mg, 1.00 mmol, 2.0 equiv) in 1,4-dioxane (1.0 ml) was stirred under N 2 for 8 h at 110 ºC. At ambient temperature, MeCN (3.0 ml), K 2 CO 3 (138 mg, 1.0 mmol) and MeI (355 mg, 2.50 mmol) were added and the mixture was stirred at 50 ºC for additional 2 h. At ambient temperature, the mixture was dry loaded onto silica gel and purified by column chromatography on silica gel (n-hexane/etoac 20:1) yielded 3e (112 mg, 67%) as a pale yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.21 (d, J = 8.5 Hz, 1H), 6.85 (d, J = 8.5 Hz, 1H), S-6

8 3.91 (s, 3H), 3.86 (s, 3H), 3.84 (s, 3H), 0.96 (s, 9H), 0.15 (s, 6H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (C q ), (CH), (C q ), 94.6 (C q ), 61.6 (CH 3 ), 55.9 (CH 3 ), 52.4 (CH 3 ), 26.1 (CH 3 ), 16.6 (C q ), -4.6 (CH 3 ). IR (neat): 2951, 2931, 2152, 1735, 1486, 1274, 1046, 810, 774 cm -1. MS (ESI) m/z (relative intensity) 357 (70) [M+Na + ], 335 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 18 H 27 O 4 Si [M+H + ] , found Methyl 2-methoxy-6-[(triisopropylsilyl)ethynyl]benzoate (3f) The general procedure GP1 was followed using benzoic acid 1f (76 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 4:1) and then HPLC yielded 3f (135 mg, 78%) as an colorless oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.27 (dd, J = 8.5, 7.8, 1H), 7.09 (dd, J = 7.8, 1.0 Hz, 1H), 6.87 (dd, J = 8.5, 1.0 Hz, 1H), 3.89 (s, 3H), 3.81 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (CH), (C q ), (CH), (C q ), (CH), (C q ), 94.7 (C q ), 56.0 (CH 3 ), 52.4 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2942, 2865, 2152, 1737, 1465, 1261, 1066, 882, 667 cm -1. MS (ESI) m/z (relative intensity) 369 (20) [M+Na + ], 347 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 20 H 31 O 3 Si [M+H + ] , found Methyl 2-ethoxy-6-[(triisopropylsilyl)ethynyl]benzoate (3g) The general procedure GP1 was followed using benzoic acid 1g (83 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by S-7

9 column chromatography on silica gel (n-hexane/etoac 20:1) yielded 3g (137 mg, 76%) as colorless oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.22 (dd, J = 8.4, 7.8 Hz, 1H), 7.06 (dd, J = 7.8, 0.9 Hz, 1H), 6.84 (dd, J = 8.4, 0.9 Hz, 1H), 4.02 (q, J = 7.0 Hz, 2H), 3.87 (s, 3H), 1.34 (t, J = 7.0 Hz, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (CH), (C q ), (CH), (C q ), (CH), (C q ), 94.5 (C q ), 64.6 (CH 2 ), 52.3 (CH 3 ), 18.5 (CH 3 ), 14.6 (CH 3 ), 11.2 (CH). IR (neat): 2943, 2865, 2156, 1738, 1458, 1260, 1065, 669 cm -1. MS (EI) m/z (relative intensity) 360 (20) [M + ], 345 (15), 329 (100). HR-MS (EI) m/z calcd for C 21 H 32 O 3 Si [M + ] , found Methyl 2-phenoxy-6-[(triisopropylsilyl)ethynyl]benzoate (3h) The general procedure GP1 was followed using benzoic acid 1h (107 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 40:1) and then HPLC yielded 3h (179 mg, 79%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = (m, 2H), (m, 2H), (m, 1H), (m, 2H), 6.83 (dd, J = 7.0, 2.4 Hz, 1H), 3.83 (s, 3H), (m, 21H). 13 C NMR (125 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (CH), (CH), (C q ), (CH), (CH), (C q ), (CH), (CH), (C q ), 95.4 (C q ), 52.4 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2943, 2865, 2157, 1735, 1453, 1234, 996, 754, 652 cm -1. MS (EI) m/z (relative intensity) 408 (20) [M + ], 393 (20), 379 (10), 377 (100). HR-MS (EI) m/z calcd for C 25 H 32 O 3 Si [M + ] , found Methyl 3,6-dimethoxy-2-[(triisopropylsilyl)ethynyl]benzoate (3i) S-8

10 The general procedure GP1 was followed using benzoic acid 1i (91 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 4:1) yielded 3i (173 mg, 92%) as a pale yellow solid. M. p. = ºC. 1 H NMR (400 MHz, CDCl 3 ) δ = 6.78 (s, 2H), 3.86 (s, 3H), 3.77 (s, 3H), 3.73 (s, 3H), (m, 21H). 13 C NMR (100 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (CH), (C q ), 99.4 (C q ), 99.4 (C q ), 56.7 (CH 3 ), 56.5 (CH 3 ), 52.3 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2942, 2864, 2157, 1732, 1483, 1254, 1055, 673 cm -1. MS (ESI) m/z (relative intensity) 399 (20) [M+Na + ], 377 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 21 H 33 O 4 Si [M+H + ] , found Methyl 2,6-bis[(triisopropylsilyl)ethynyl]benzoate (3j) The general procedure GP1 was followed using benzoic acid 1j (61 mg, 0.50 mmol) (bromoethynyl)triisopropylsilane (2a) (326 mg, 1.25 mmol, 2.50 equiv) and K 2 CO 3 (207 mg, 1.50 mmol, 3.0 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 30:1) and then by HPLC yielded 3j (144 mg, 58%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.42 (d, J = 7.7 Hz, 2H), 7.25 (t, J = 7.7 Hz, 1H), 3.88 (s, 3H), (m, 42H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (CH), (CH), (C q ), (C q ), 95.4 (C q ), 52.5 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2942, 2863, 2155, 1737, 1458, 1268, 1113, 882, 669 cm -1. MS (EI) m/z (relative intensity) 497 (5) [M+H + ], 496 (10) [M + ], 481 (30), 465 (100), 463 (10). HR-MS (ESI) m/z calcd for C 30 H 49 O 2 Si 2 [M+H + ] , found S-9

11 Methyl 3,4,5-trifluoro-2,6-bis[(triisopropylsilyl)ethynyl]benzoate (3k) The general procedure GP1 was followed using benzoic acid 1k (88 mg, 0.50 mmol), (bromoethynyl)triisopropylsilane (2a) (326 mg, 1.25 mmol, 2.50 equiv) and K 2 CO 3 (207 mg, 1.50 mmol, 3.0 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 25:1) yielded 3k (231 mg, 84%) as a pale yellow oil. 1 H NMR (400 MHz, CDCl 3 ) δ = 3.87 (s, 3H), (m, 42H). 13 C NMR (100 MHz, CDCl 3 ) δ = (t, 4,4 J C-F = 2.6 Hz, C q ), (ddd, 1,2,3 J C-F = 259.7, 11.0, 3.7 Hz, C q ), (dt, 1,2,2 J C-F = 255.8, 15.4 Hz, C q ), (d, 3 J C-F = 3.5, C q ), (dd, 2,3 J C-F = 12.8, 7.2 Hz, C q ), (t, 3,3 J C-F = 3.3, C q ), 94.0 (d, 4 J C-F = 3.4, C q ), 53.0 (CH 3 ), 18.5 (CH 3 ), 11.1 (CH). 19 F NMR (376 MHz, CDCl 3 ) δ = (d, J = 21.0 Hz), (t, J = 21.0 Hz). IR (neat): 2944, 2866, 2141, 1749, 1460, 1218, 964, 882, 662 cm -1. MS (ESI) m/z (relative intensity) 573 (100) [M+Na + ], 551 (50) [M+H + ]. HR- MS (ESI) m/z calcd for C 30 H 45 F 3 O 2 Si 2 Na [M+Na + ] , found Methyl 3,4,5-trimethoxy-2,6-bis[(triisopropylsilyl)ethynyl]benzoate (3l) The general procedure GP1 was followed using benzoic acid 1l (106 mg, 0.50 mmol) (bromoethynyl)triisopropylsilane (2a) (326 mg, 1.25 mmol, 2.50 equiv) and K 2 CO 3 (207 mg, 1.50 mmol, 3.0 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 20:1) yielded 3l (266 mg, 91%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 3.93 (s, 6H), 3.86 (s, 3H), 3.85 (s, 3H), (m, 42H). 13 C NMR (125 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), 99.0 (C q ), 98.6 (C q ), 61.4 (CH 3 ), 61.4 (CH 3 ), 52.6 (CH 3 ), 18.7 (CH 3 ), 11.4 (CH). IR (neat): 2939, 2863, 2157, 1739, S-10

12 1460, 1348, 1025, 660 cm -1. MS (ESI) m/z (relative intensity) 609 (40) [M+Na + ], 587 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 33 H 55 O 5 Si 2 [M+H + ] , found Methyl 3,4-dimethoxy-2,6-bis[(triisopropylsilyl)ethynyl]benzoate (3m) The general procedure GP1 was followed using benzoic acid 1m (91 mg, 0.50 mmol), (bromoethynyl)triisopropylsilane (2a) (326 mg, 1.25 mmol, 2.50 equiv) and K 2 CO 3 (207 mg, 1.50 mmol, 3.0 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 30:1) and then by HPLC yielded 3m (197 mg, 71%) as a light yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 6.86 (s, 1H), 3.83 (s, 3H), 3.80 (s, 3H), 3.79 (s, 3H), (m, 42H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), (C q ), (CH), (C q ), (C q ), 98.8 (C q ), 94.2 (C q ), 61.0 (CH 3 ), 56.2 (CH 3 ), 52.5 (CH 3 ), 18.6 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH), 11.3 (CH). IR (neat): 2942, 2865, 2158, 1740, 1463, 1240, 881, 662 cm -1. MS (ESI) m/z (relative intensity) 579 (50) [M+Na + ], 557 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 32 H 53 O 4 Si 2 [M+H + ] , found Methyl 3-[(triisopropylsilyl)ethynyl]-[1,1'-biphenyl]-2-carboxylate (3n) The general procedure GP1 was followed using benzoic acid 1n (99 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 25:1) and then by HPLC yielded 3n (126 mg, 64%) as a pale yellow oil. 1 H NMR (400 MHz, CDCl 3 ) δ = 7.52 (dd, J = 7.6, 1.3 Hz, 1H), (m, 7H), 3.63 (s, 3H), (m, 21H). 13 C NMR (100 MHz, CDCl 3 ) δ = S-11

13 168.7 (C q ), (C q ), (C q ), (C q ), (CH), (CH), (CH), (CH), (CH), (CH), (C q ), (C q ), 94.9 (C q ), 52.1 (CH 3 ), 18.6 (CH 3 ), 11.2 (CH). IR (neat): 2943, 2864, 2157, 1736, 1457, 1260, 896, 744, 667 cm -1. MS (ESI) m/z (relative intensity) 415 (10) [M+Na + ], 393 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 25 H 33 O 2 Si [M+H + ] , found Methyl 2-(trifluoromethyl)-6-[(triisopropylsilyl)ethynyl]benzoate (3o) The general procedure GP1 was followed using benzoic acid 1o (95 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 30:1) and then by HPLC yielded 3o (133 mg, 69%) as a pale yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.69 (ddd, J = 7.8, 1.3, 0.6 Hz, 1H), 7.61 (ddd, J = 8.0, 1.3, 0.6 Hz, 1H), (m, 1H), 3.93 (s, 3H), (m, 21H). 13 C NMR (125 MHz, CDCl 3 ) δ = (C q ), (q, 4 J C-F = 1.1 Hz, CH), (q, 3 J C-F = 2.3 Hz, C q ), (CH), (q, 2 J C-F = 32.5 Hz, C q ), (q, 3 J C-F = 4.6 Hz, CH), (q, 1 J C-F = Hz, C q ), (C q ), (C q ), 97.1 (C q ), 52.9 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). 19 F NMR (282 MHz, CDCl 3 ) δ = (s). IR (neat): 2945, 2866, 2157, 1745, 1457, 1321, 1132, 909, 666 cm -1. MS (EI) m/z (relative intensity) 385 (5) [M+H + ], 365 (60), 353 (100). HR-MS (ESI) m/z calcd for C 20 H 27 F 3 O 2 SiNa [M+Na + ] , found Methyl 5-acetyl-2-[(triisopropylsilyl)ethynyl]benzoate (3p) The general procedure GP1 was followed using benzoic acid 1p (82 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by S-12

14 column chromatography on silica gel (n-hexane/etoac 30:1) and then by HPLC yielded 3p (72 mg, 40%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 8.43 (d, J = 1.9 Hz, 1H), 8.00 (dd, J = 8.2, 1.9 Hz, 1H), 7.66 (d, J = 8.2 Hz, 1H), 3.93 (s, 3H), 2.62 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (CH), (C q ), (CH), (CH), (C q ), (C q ), (C q ), 52.4 (CH 3 ), 26.6 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2942, 2864, 2157, 1725, 1684, 1236, 1072, 880, 605 cm -1. MS (ESI) m/z (relative intensity) 381 (100) [M+Na + ], 359 (60) [M+H + ]. HR-MS (ESI) m/z calcd for C 21 H 31 O 3 Si [M+H + ] , found Methyl 2-fluoro-6-[(triisopropylsilyl)ethynyl]benzoate (3q) The general procedure GP1 was followed using benzoic acid 1q (70 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 20:1) and then by HPLC yielded 3q (127 mg, 76%) as a pale yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ = (m, 2H), (m, 1H), 3.90 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (d, 1 J C-F = Hz, C q ), (d, 3 J C-F = 9.1 Hz, CH), (d, 4 J C-F = 3.4 Hz, CH), (d, 2 J C-F = 17.5 Hz, C q ), (d, 3 J C-F = 4.3 Hz, C q ), (d, 2 J C-F = 21.6 Hz, CH), (d, 4 J C-F = 3.9 Hz, C q ), 96.5 (C q ), 52.7 (CH 3 ), 18.6 (CH 3 ), 11.2 (CH). 19 F NMR (283 MHz, CDCl 3 ) δ = -( ) (m). IR (neat): 2944, 2865, 2156, 1740, 1460, 1276, 997, 882, 667 cm -1. MS (ESI) m/z (relative intensity) 357 (50) [M+Na + ], 335 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 19 H 28 O 2 FSi [M+H + ] , found S-13

15 Methyl 2-chloro-6-[(triisopropylsilyl)ethynyl]benzoate (3r) The general procedure GP1 was followed using benzoic acid 1r (78 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 4:1) and then by HPLC yielded 3r (128 mg, 73%) as an oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.39 (dd, J = 7.5, 1.3 Hz, 1H), 7.32 (dd, J = 8.1, 1.3 Hz, 1H), 7.25 (d, J = 7.6 Hz, 1H), 3.91 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (CH), (C q ), (CH), (CH), (C q ), (C q ), 96.3 (C q ), 52.7 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2944, 2866, 2169, 1744, 1444, 1270, 1109, 902, 670 cm -1. MS (EI) m/z (relative intensity) 349 (10) [M H + ], 343 (5), 335 (5), 319 (100). HR-MS (ESI) m/z calcd for C 19 H 28 ClO 2 Si [M+H + ] , found Methyl 2-bromo-6-[(triisopropylsilyl)ethynyl]benzoate (3s) The general procedure GP1 was followed using benzoic acid 1s (100 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac 40:1) and then by HPLC yielded 3s (102 mg, 52%) as an oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.51 (dd, J = 8.1, 1.1 Hz, 1H), 7.45 (dd, J = 7.8, 1.1 Hz, 1H), 7.19 (dd, J = 8.1, 7.8 Hz, 1H), 3.93 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (CH), (CH), (CH), (C q ), (C q ), (C q ), 96.4 (C q ), 52.7 (CH 3 ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2943, 2865, 2164, 1741, 1462, 1268, 1104, 878, 666 cm -1. MS (ESI) m/z (relative intensity) 353 (100) [M-41], 413 (25), 403 (25), 395 (20). HR-MS (ESI) m/z calcd for C 19 H BrO 2 SiNa [M+Na + ] , found S-14

16 3,4,6-Trimethoxy-2-[(triisopropylsilyl)ethynyl]benzoic acid (7a) The general procedure GP2 was followed using benzoic acid 1a (106 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 4:1:0.02) yielded 7a (161 mg, 82%) as a colorless solid. M. p. = ºC. 1 H NMR (400 MHz, CDCl 3 ) δ = 6.48 (s, 1H), 3.88 (s, 3H), 3.85 (s, 3H), 3.83 (s, 3H), (m, 21H). 13 C NMR (100 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), (C q ), (C q ), 98.9 (C q ), 97.9 (CH), 60.9 (CH 3 ), 56.8 (CH 3 ), 56.2 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2942, 2864, 2163, 1699, 1583, 1209, 1096, 691 cm -1. MS (ESI) m/z (relative intensity) 415 (30) [M+Na + ], 393 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 21 H 33 O 5 Si [M+H + ] , found ,6-Dimethoxy-2-[(triisopropylsilyl)ethynyl]benzoic acid (7b) The general procedure GP2 was followed using benzoic acid 1i (91 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 4:1:0.02) yielded 7b (174 mg, 96%) as a white solid. M.p. = C. 1 H NMR (300 MHz, CDCl 3 ) δ = 6.80 (d, J = 9.2 Hz, 1H), 6.77 (d, J = 9.2 Hz, 1H), 3.76 (s, 3H), 3.74 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (CH), (C q ), (C q ), 99.1 (C q ), 57.0 (CH 3 ), 56.6 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2939, 2863, 2154, 1703, 1258, 1061, 881, 660, 457 cm -1. MS (ESI) m/z (relative intensity) S-15

17 385 (55) [M+Na + ], 363 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 20 H 31 O 4 Si [M+H + ] , found [(Triisopropylsilyl)ethynyl]-1-naphthoic acid (7c) The general procedure GP2 was followed using benzoic acid 1t (86 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 10:1:0.02) yielded 7c (100 mg, 57%) as a pale yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ = 8.13 (ddd, J = 8.5, 1.8, 0.8 Hz, 1H), (m, 2H), (m, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (CH), (C q ), (CH), (CH), (CH), (CH), (CH), (C q ), (C q ), 97.4 (C q ), 18.7 (CH 3 ), 11.4 (CH). IR (neat): 2942, 2864, 2128, 1697, 1462, 1256, 820, 744, 648 cm -1. MS (EI) m/z (relative intensity) 352 (5) [M + ], 309 (100), 267 (10), 249 (10), 239 (30), 179 (10), 151 (10). HR-MS (EI) m/z calcd for C 22 H 28 O 2 Si [M + ] , found ,3-Dimethoxy-6-[(triisopropylsilyl)ethynyl]benzoic acid (7d) The general procedure GP2 was followed using benzoic acid 1d (91 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 4:1:0.02) yielded 7d (173 mg, 96%) as a colorless solid. M. p. = ºC. 1 H NMR (400 MHz, CDCl 3 ) δ = 7.25 (d, J = 8.5 Hz, 1H), 6.88 (d, J = 8.5 Hz, 1H), 3.88 (s, 3H), 3.87 (s, 3H), (m, 21H). 13 C NMR (100 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), S-16

18 114.0 (C q ), (CH), (C q ), 93.7 (C q ), 61.7 (CH 3 ), 56.0 (CH 3 ), 18.6 (CH 3 ), 11.2 (CH). IR (neat): 2941, 2890, 2154, 1703, 1459, 1274, 1045, 812, 676 cm -1. MS (ESI) m/z (relative intensity) 385 [M+Na + ] (50), 363 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 20 H 31 O 4 Si [M+H + ] , found [(Triisopropylsilyl)ethynyl]-[1,1'-biphenyl]-2-carboxylic acid (7e) The general procedure GP2 was followed using benzoic acid 1n (99 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 10:1:0.02) yielded 7e (168 mg, 89%) as a pale yellow syrup. 1 H NMR (300 MHz, CDCl 3 ) δ = (s br, 1H), 7.58 (dd, J = 7.6, 1.3 Hz, 1H), (m, 7H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (CH), (CH), (CH), (CH), (CH), (C q ), (C q ), 96.0 (C q ), 18.7 (CH 3 ), 11.3 (CH). IR (neat): 2942, 2864, 2159, 1693, 1437, 1288, 1275, 880, 665 cm -1. MS (ESI) m/z (relative intensity) 401 (100) [M+Na + ], 379 (90) [M+H + ]. HR-MS (ESI) m/z calcd for C 24 H 30 O 2 SiNa [M+Na + ] , found (Trifluoromethyl)-6-[(triisopropylsilyl)ethynyl]benzoic acid (7f) The general procedure GP2 was followed using benzoic acid 1o (95 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 15:1:0.02) yielded 7f (175 mg, 95%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = (s, S-17

19 1H), 7.66 (d, J = 8.3 Hz, 1H), 7.57 (d, J = 7.9 Hz, 1H), (m, 1H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (CH), (q, 4 J C-F = 2.1 Hz, C q ), (CH), (q, 2 J C-F = 32.7 Hz, C q ), (q, 3 J C-F = 4.6 Hz, CH), (q, 1 J C-F = Hz, C q ), (C q ), (C q ), 98.2 (C q ), 18.5 (CH 3 ), 11.2 (CH). 19 F NMR (282 MHz, CDCl 3 ) δ = (s). IR (neat): 2943, 2866, 2160, 1712, 1462, 1323, 1131, 665 cm -1. MS (ESI) m/z (relative intensity) 393 (100) [M+Na + ], 371 (10) [M+H + ]. HR-MS (ESI) m/z calcd for C 19 H 25 F 3 O 2 SiNa [M+Na + ] , found Methoxy-6-[(triisopropylsilyl)ethynyl]benzoic acid (7g) The general procedure GP2 was followed using benzoic acid 1f (76 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 10:1:0.02) yielded 7g (151 mg, 91%) as a white solid. M.p. = C. 1 H NMR (300 MHz, CDCl 3 ) δ = 7.24 (dd, J = 8.4, 7.7 Hz, 1H), 7.08 (dd, J = 7.7, 1.0 Hz, 1H), 6.85 (dd, J = 8.5, 1.0 Hz, 1H), 3.80 (s, 3H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (CH), (CH), (C q ), (C q ), (CH), (C q ), 96.0 (C q ), 56.0 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2940, 2863, 2148, 1697, 1463, 1278, 1080, 881, 665 cm -1. MS (ESI) m/z (relative intensity) 355 (100) [M+Na + ], 333 (70) [M+H + ]. HR-MS (ESI) m/z calcd for C 19 H 29 O 3 Si [M+H + ] , found S-18

20 2-Phenoxy-6-[(triisopropylsilyl)ethynyl]benzoic acid (7h) The general procedure GP2 was followed using benzoic acid 1h (107 mg, 0.50 mmol) and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv). Purification by column chromatography on silica gel (n-hexane/etoac/acoh 20:1:0.02) yielded 7h (181 mg, 92%) as a white solid. M.p. = C. 1 H NMR (300 MHz, CDCl 3 ) δ = (m, 2H), (m, 2H), (m, 1H), (m, 2H), 6.73 (dd, J = 5.6, 3.8 Hz, 1H), (m, 21H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (CH), (CH), (CH), (C q ), (CH), (C q ), (CH), (CH), (C q ), 96.6 (C q ), 18.5 (CH 3 ), 11.2 (CH). IR (neat): 2940, 2863, 2158, 1703, 1571, 1456, 1238, 997, 654 cm -1. MS (ESI) m/z (relative intensity) 417 (100) [M+Na + ], 395 (80) [M+H + ]. HR-MS (ESI) m/z calcd for C 24 H 31 O 3 Si [M+H + ] , found ,5-Dimethoxy-4-methyl-2,6-bis[(triisopropylsilyl)ethynyl]benzoic acid (7i) The general procedure GP2 was followed using benzoic acid 1u (98 mg, 0.50 mmol) (bromoethynyl)triisopropylsilane (2a) (326 mg, 1.25 mmol, 2.50 equiv) and K 2 CO 3 (207 mg, 1.50 mmol, 3.0 equiv). Purification by column chromatography on silica gel (nhexane/etoac/acoh 10:1:0.02) yielded 7i (197 mg, 71%) as a pale yellow solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = 3.94 (s, 6H), 2.23 (s, 3H), (m, 42H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), (C q ), 99.0 (C q ), 60.7 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH), 9.6 (CH 3 ). IR (neat): 2942, 2865, 2153, 1703, 1450, 1389, 994, 882, 661 cm -1. MS (EI) m/z (relative intensity) 557 (3) [M+H + ], 556 (5) [M + ], 537 (10), 515 (15), 514 (40), 513 (100), 455 (5). HR-MS (EI) m/z calcd for C 32 H 52 O 4 Si 2 [M + ] , found S-19

21 C H Alkynylation/Cyclization Cascade (Z)-7-Methyl-3-[(triisopropylsilyl)methylene]isobenzofuran-1(3H)-one (5a) A suspension of [RuCl 2 (p-cymene)] (4) (15.3 mg, 5.0 mol %), X-phos (23.8 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol), benzoic acid 1v (68 mg, 0.50 mmol), and (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv) in NMP (2.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, the mixture was diluted with MTBE (120 ml), then sequentially washed with H 2 O (20 ml) and brine (20 ml). The organic phase was dried over Na 2 SO 4, and concentrated in vacuo. The remaining residue was purified by column chromatography on silica gel (n-hexane/etoac 20:1) yielded 5a (125 mg, 79%) as a colorless solid. M. p. = ºC. 1 H NMR (300 MHz, CDCl 3 ) δ = (m, 2H), (m, 1H), 5.53 (s, 1H), 2.69 (s, 3H), (m, 3H), 1.11 (d, J = 7.2 Hz, 18H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (CH), (C q ), (CH), 99.7 (CH), 18.8 (CH 3 ), 17.5 (CH 3 ) 11.7 (CH). IR (ATR): 2940, 2863, 1762, 1637, 1461, 1255, 974 cm -1. MS (ESI) m/z (relative intensity) 339 (90) [M+Na + ], 317 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 19 H 29 O 2 Si [M+H + ] , found The analytical data are in accordance with those previously reported in the literature. [4] (Z)-3-[(Triisopropylsilyl)methylene]naphtho[1,2-c]furan-1(3H)-one (5b) A suspension of [Ru(Cl) 2 (p-cymene)] (4) (15.3 mg, 5.0 mol %), X-phos (23.8 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol), benzoic acid 1t (86 mg, 0.50 mmol), and S-20

22 (bromoethynyl)triisopropylsilane (2a) (170 mg, 0.65 mmol, 1.30 equiv) in NMP (2.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, the mixture was diluted with MTBE (120 ml), then sequentially washed with H 2 O (20 ml) and brine (20 ml). The organic phase was dried over Na 2 SO 4, and concentrated in vacuo. The remaining residue was purified by column chromatography on silica gel (n-hexane/etoac 20:1) yielded 5b (123 mg, 70%) as a colorless solid. M. p. = ºC. 1 H NMR (400 MHz, CDCl 3 ) δ = (m, 1H), 8.09 (d, J = 8.4 Hz, 1H), 7.92 (d, J = 8.2 Hz, 1H), (m, 2H), 7.60 (ddd, J = 8.2, 7.0, 1.3 Hz, 1H), 5.71 (s, 1H), 1.38 (dq, J = 14.3, 7.4 Hz, 3H), 1.13 (d, J = 7.4 Hz, 18H). 13 C NMR (100 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (CH), (C q ), (CH), (C q ), (CH), (CH), (CH), (C q ), (CH), (CH), 18.8 (CH 3 ), 11.7 (CH). IR (ATR): 2940, 2862, 1755, 1633, 1458, 1111, 963, 751 cm -1. MS (ESI) m/z (relative intensity) 375 (30) [M+Na + ], 353 (10) [M+H + ], 117 (100). HR-MS (ESI) m/z calcd for C 22 H 29 O 2 Si [M+H + ] , found The analytical data are in accordance with those previously reported in the literature. [4] Mechanistic Studies a) H-D exchange experiment A suspension of 3,4,5-trimethoxybenzoic acid (1l) (159 mg, 0.75 mmol), (bromoethynyl)triisopropylsilane (2a) (131 mg, 0.50 mmol), [Ru(O 2 CMes) 2 (p-cymene)] (4) (28.1 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol) in a solvent mixture of 1,4-dioxane (2.0 ml) and CD 3 OD (0.1 ml) was stirred at 120 ºC for 16 h in a sealed tube under N 2 atmosphere. At ambient temperature, MeCN (3.0 ml), K 2 CO 3 (207 mg, 1.50 mmol) and MeI (355 mg, 2.50 mmol) were added and the mixture was stirred at 50 ºC for another 2.0 h. At ambient S-21

23 temperature, the mixture was dry-loaded onto silica gel and purified by column chromatography on silica gel (n-hexane/etoac 20:1) to yield [D] n -1l (90 mg, 53%) and 3l (81 mg, 18%). Only trace amount of mono-alkynylation product was observed. The D- incorporation in [D] n -1l was estimated by 1 H-NMR spectroscopy. b) Probing Radical Intermediates S-22

24 Reaction in the presence of TEMPO 1a (106 mg, 0.5 mmol, 1.0 equiv), (2a) (170 mg, 0.65 mmol, 1.3 equiv), [Ru(O 2 CMes) 2 (pcymene)] (4) (28.1 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol) and TEMPO (78 mg, 0.5 mmol, 1.0 equiv) were placed into a 25 ml Schlenk tube equipped with a septum under N 2 atmosphere. 1,4-Dioxane (2.0 ml) was introduced via cannula. The reaction mixture was stirred at 120 C for 16 h. At ambient temperature, MeCN (3.0 ml), K 2 CO 3 (207 mg, 1.50 mmol) and MeI (355 mg, 2.50 mmol) were added and the mixture was stirred at 50 ºC for another 2 h. At ambient temperature, the mixture was dry-loaded onto silica gel and purified by column chromatography on silica gel (n-hexane/etoac 4:1) to yield 3a (177 mg, 87%) as an off-white solid. Reaction in the presence of BHT 1a (106 mg, 0.5 mmol, 1.0 equiv), (2a) (170 mg, 0.65 mmol, 1.3 equiv), [Ru(O 2 CMes) 2 (pcymene)] (4) (28.1 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol) and 2,6-bis(1,1- dimethylethyl)-4-methylphenol (110 mg, 0.5 mmol, 1.0 equiv) were placed into a 25 ml Schlenk tube equipped with a septum under N 2 atmosphere. 1,4-Dioxane (2.0 ml) was introduced via cannula. The reaction mixture was stirred at 120 C for 16 h. At ambient temperature, MeCN (3.0 ml), K 2 CO 3 (207 mg, 1.50 mmol) and MeI (355 mg, 2.50 mmol) were added and the mixture was stirred at 50 ºC for another 2 h. At ambient temperature, the mixture was dry-loaded onto silica gel and purified by column chromatography on silica gel (n-hexane/etoac 4:1) to yield 3a (142 mg, 70%) as an off-white solid. S-23

25 c) Competition Experiment Intermolecular competition experiment between benzoic acid 1f and 1o A suspension of (2a) (170 mg, 0.65 mmol, 1.3 equiv.), 2-methoxylbenzoic acid (1f) (76 mg, 0.50 mmol), 2-(trifluoromethyl)benzoic (1o) (95 mg, 0.50 mmol), [Ru(O 2 CMes) 2 (p-cymene)] (28.1 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol) in 1,4-dioxane (1.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, MeCN (3.0 ml), K 2 CO 3 (207 mg, 1.50 mmol) and MeI (355 mg, 2.50 mmol) were added and the mixture was stirred at 50 ºC for another 2 h. At ambient temperature, 1,3,5-trimethoxybenzene (16.8 mg, 0.1 mmol) was added as internal standard, the conversion of 3f and 3o was determined based on crude 1 H-NMR analysis. S-24

26 Traceless Removal of Silyl Group 3a (203 mg, 0.50 mmol) was dissolved in THF (3 ml) and TBAF (1.0 M in THF, 1.50 ml) was then added at ambient temperature with constant stirring for 12 h. Then, the mixture was concentrated in vacuo. The residue was dissolved in H 2 O (30 ml) and extracted with EtOAc (3 5 ml). The combined organic layers were washed with brine (10 ml), dried over Na 2 SO 4, filtered and evaporated in vacuo. The crude product was purified by column chromatography to afford the alkyne 6 (118 mg, 94% yield) as an off-white solid. Methyl 2-ethynyl-3,4,6-trimethoxybenzoate (6) M.p. = C. 1 H NMR (300 MHz, CDCl 3 ) δ = 6.54 (s, 1H), 3.91 (s, 3H), 3.90 (s, 3H), 3.87 (s, 3H), 3.84 (s, 3H), 3.39 (s, 1H). 13 C NMR (75 MHz, CDCl 3 ) δ = (C q ), S-25

27 (C q ), (C q ), (C q ), (C q ), (C q ), 98.5 (CH), 84.7 (C q ), 76.5 (CH), 61.0 (CH 3 ), 56.5 (CH 3 ), 56.0 (CH 3 ), 52.3 (CH 3 ). IR (neat): 3265, 2950, 1721, 1585, 1269, 1208, 1027, 814, 650 cm -1. MS (ESI) m/z (relative intensity) 273 (60) [M+Na + ], 251 (100) [M+H + ]. HR-MS (ESI) m/z calcd for C 13 H 15 O 5 [M+H + ] , found Decarboxylative C H Alkynylation A suspension of [Ru(O 2 CMes) 2 (p-cymene)] (4) (28.1 mg, 10 mol %), K 2 CO 3 (138 mg, 1.00 mmol), benzoic acid 1a (106 mg, 0.50 mmol), and alkynyl bromide (2a) (170 mg, 0.65 mmol) in 1,4-dioxane (1.0 ml) was stirred under N 2 for 16 h at 120 ºC. At ambient temperature, the solvent was removed and AcOH (2.0 ml) was added under N 2 atmosphere, and the mixture was stirred at 150 ºC for 16 h. At ambient temperature, the mixture was dry-loaded onto silica gel and purified by column chromatography (n-hexane/etoac) to yield the product 8 (132 mg, 76%) as pale yellow oil and cyclic product 5c (27 mg, 14% ) as a pale yellow solid. Triisopropyl[(2,3,5-trimethoxyphenyl)ethynyl]silane (8) 1 H NMR (400 MHz, CDCl 3 ) δ = 6.47 (d, J = 2.9 Hz, 1H), 6.45 (d, J = 2.9 Hz, 1H), 3.83 (s, 3H), 3.80 (s, 3H), 3.75 (s, 3H), 1.12 (s, 21H). 13 C NMR (100 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (CH), (C q ), (CH), 94.9 (C q ), 61.0 (CH 3 ), 55.9 (CH 3 ), 55.6 (CH 3 ), 18.6 (CH 3 ), 11.3 (CH). IR (neat): 2941, 2865, 2152, 1686, 1463, 1153, 1055, 882, 668 cm -1. MS (EI) m/z (relative intensity) 349 (15) [M+H + ], 348 (70) [M + ], 305 (85), 290 (100), 277 (20), 263 (30), 248 (40), 220 (30). HR-MS (EI) m/z calcd for C 20 H 32 O 3 Si [M + ] , found S-26

28 (Z)-4,5,7-Trimethoxy-3-[(triisopropylsilyl)methylene]isobenzofuran-1(3H)-one (5c) M.P. = ºC; 1 H NMR (300 MHz, CDCl 3 ) δ = 6.48 (s, 1H), 5.95 (s, 1H), 3.95 (s, 3H), 3.94 (s, 3H), 3.82 (s, 3H), (m, 3H), 1.06 (d, J = 7.3 Hz, 18H). 13 C NMR (125 MHz, CDCl 3 ) δ = (C q ), (C q ), (C q ), (C q ), (C q ), (C q ), (CH), (C q ), 97.8 (CH), 59.9 (CH 3 ), 56.6 (CH 3 ), 56.4 (CH 3 ), 18.8 (CH 3 ), 11.6 (CH). IR (neat): 2938, 2863, 1763, 1602, 1505, 1323, 1231, 1043, 967 cm -1. MS (EI) m/z (relative intensity) 393 (30) [M+H + ], 392 (80) [M + ], 391 (15), 378 (20), 377 (100), 361 (30). HR-MS (EI) m/z calcd for C 21 H 33 O 5 Si [M + ] , found S-27

29 References [1] Ackermann, L.; Vicente, R.; Potukuchi, H. K.; Pirovano, V. Org. Lett. 2010, 12, [2] Frei, R. ; Waser, J. J. Am. Chem. Soc. 2013, 135, [3] Jiang, M.; Rawat, M.; Wulff, W. D. J. Am. Chem. Soc. 2004, 126, [4] a) Liu, Y.; Yang, Y.; Shi, Y.; Wang, X.; Zhang, L.; Cheng, Y.; You, J. Organometallics. 2016, 35, b) Mei, R.; Zhu, C.; Ackermann, L. Chem. Commun. 2016, 52, S-28

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