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2.4.2.3.1 Synthesis of Aryl- and Hetarylsilanes

DOI: 10.1055/sos-SD-208-00340

Szabó, K. J.Science of Synthesis: Cross Coupling and Heck-Type Reactions, (20132513.

Aromatic C—H silylation and borylation (see Section 2.4.2.2.1.1) show some clear analogies. (Cycloocta-1,5-diene)(methoxy)iridium(I) dimer, which has been successfully employed in several C—H borylation reactions, is also an active catalyst in silylations. Furthermore, the most usual catalyst sources in silylation are based on iridium, ruthenium, and platinum complexes, and, recently, even palladium-catalyzed reactions have appeared. Falck and Lu have published a useful C—H silylation reaction for various hetarenes (Table 2).[‌53‌] In these studies (cycloocta-1,5-diene)(methoxy)iridium(I) dimer is employed in the presence of 4,4′-di-tert-butyl-2,2′-bipyridyl, as in Hartwigʼs[‌13‌,‌15‌] borylation reactions (see Scheme 8, Section 2.4.2.2.1.1). The inexpensive reagent triethylsilane (6) is used as the silane source, affording heteroaromatic silanes, usually in high yields. The reactions are performed in the presence of norbornene, which serves as a sacrificial hydrogen acceptor. The C—H silylation reaction works well with indole derivatives bearing electron-donating substituents (Table 2, entry 1) but also with other heterocycles, such as benzo[b]thiophene or benzo[b]furan (entries 4 and 5). In the case of electron-withdrawing substituents, or where the position β to the heteroatom in the substrate is sterically hindered (Table 2, entry 2), the reaction is relatively slow and the yields drop. The high α-selectivity is probably a result of chelation control, as substitution of the nitrogen atom (Table 2, entry 3) leads to a shift in the selectivity to the formation of the 3-substituted indole derivative.

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Meeee Meeeeeeee Meeeeee Meeee (%) Mee
8 88 [‌88‌]
8 88 [‌88‌]
8 88 [‌88‌]
8 88 [‌88‌]
8 88 [‌88‌]

Meeeeee eee Meeeeee eeee eeeeeeeee ee eeeee-eeeeeeeee eeeeeee-eeeeeeeee M—M eeeeeeeeee eeeeeee (Meeeee 88).[‌88‌] Me eeee eeeeeeeee, eeeeeee eee eeeeeeeee 88 eee eeeeeee eeee eeeeeeeeeeeee ee eee eeeeeeee ee (eeeeeeeee-8,8-eeeee)(eeeeeee)eeeeeee(M) eeeee ee eeeeee eeeee eeeeee 88. Mee ee eeee eeeeee eeeee eeeeee 88 eeeeeee eeeeeeeeeeeeeee eeeeeeeeeee eeeeeeeee 8,8-eeeeeee-8,8-eeeeeeeeeeeee eeeeeeeeeee 88. Me eeee eeeeeee, eeeeeeeeee ee eeeee eeee ee e eeeeeeeeeee eeeeeeee eeeeeeee. 8,8-Meeeeee-8,8-eeeeeeeeeeeeee 88 eee ee eeeeeeeee ee Meeee eeeeeeeee ee eeee eeeeee eeeeeeeeeee, ee Meeeee eeeeeeee eeee eeee eeeeeee ee eee eeeeeeee ee e eeeeeeeee eeeeeeee. Meeeee eeeeeeee eeeeeee e eeeeeee eee-eeee eeeeeeeee ee 8,8-eeeeeee-8,8-eeeeeeeeeeeee eeeeeeeeeee. Mee Meeeeee eeeee eee eeee eeeeeeeee eeeeeee eeeeeeeee eeeee e eeeeeeee eeeeeeee;[‌88‌] eeeeeee, (eeeeeeeee-8,8-eeeee)(eeeeeee)eeeeeee(M) eeeee ee eeee eeeeee eeee eee eeeeeeee eeeeeeeee eeeeee eee eeeeee eee M—M eeeeeeeeee ee ee eeeeeeeee eeeee eeee eeeeeeeeee.

Meeeee 88 eeeee-Meeeeeee M—M Meeeeeeeee[‌88‌]

Meeeeeeeeee 88

M8 M8 Meeee (%) Mee
M Me 88 [‌88‌]
M Me 88 [‌88‌]
MM8 Me 88 [‌88‌]
MM8 M 88 [‌88‌]
M M 88 [‌88‌]

Meeeeeee eee Meeee eeee eeeeeeee ee eeeeeeeeeee eeeeeeeeeee eeeee e eeeeeeeee eeeee-eeeeeeeee eeeee (Meeeee 88).[‌88‌] Me eeee eeeeeee, eeeeeeeeeee eeeee 88 eee eeeeeee eeee 8-(8M-eeeeeee-8-ee)eeeeeee (88) ee eeeeeee e eeeeeeeee eeeee (eee) eeee eee eeeee. Mee eeeeeeeee eeeeeeee eeeeeeeeee 88 ee eeeeeee eeee eeeeeeeeeeeeee (8) ee eee eeeeeeee ee e eeeeeeeee eeeeeeee. Mee eeeee ee eeeee eeeeeee eee eeeee eeeeeeeeeeeee ee eee eeeee eeeeeeee, eeeeeeeeee eee eeeeeeeee ee eeeeeeeee. Meee eee eeeeeeee ee eeeeeeee, eee eeeeeeeee eeeee ee eeeeeeeeee 88 eee ee eeeeeeee ee e eeeeeee eeeee, eeeeeeeee eeeeeeeeeeeeee eeeeeeeeee eeeeeeee 88. Mee eeeeeeee eeeee eeee eee eeeeeee eeeeeeeee ee eeeeeeeeeee eeeee 88. Meeeee eeeeeeeeee ee eeeeeeee eee eeeeeeeeee eeeeeee eeeeeeee-eeeeeeee eeeeee eeee eee eeeee eeeeeee eeeeeeee-eeeeeeeeeee eeeeee.

Meeeee 88 eeeee-Meeeeeee M—M Meeeeeeeee Meeee e 8-(8M-Meeeeee-8-ee)eeeeeee-Meeee Meeeeeeee Meeee[‌88‌]

Meeeeeeeeee 88

M8 M8 Meeee (%) Mee
MMe M 88 [‌88‌]
M M 88 [‌88‌]
MM8Me M 88 [‌88‌]
M Me 88 [‌88‌]

Mee eee ee-eeeeeee eeee eeeeeeee e eeeeeeee-eeeeeeeee eeeee M—M eeeeeeeeee eeeeeee.[‌88‌] Me eeee eeeeeeee, eeeeee eeeeee (e.e., MMe) eeeee ee eeeeeeeee eeeeee. Meeee ee eeeeeeee eeeeeeee eeeeeeeeeeeee, ee eee eeee eeeee eeee eee eeeeeeeee eeeeee ee eeeeeee eee eeeeeeeee ee eeeeeeeee ee Me—M eeeee. M—M eeeeeeeeee eee eeee ee eeeeeeeee ee eee eeeeeee ee eeeeeeeee eeeeee. Meeeeee, ee eeeee eeeeeeeee eeee eeee eeeeeeeeeeee eee eeeeeeee, eeeeeeeee ee eeeeeeeeeee eeeeee. Meeeeee eee Meeeeee eeee eeeee eeee eeeeeee eee ee eeeeeeeee eeeee e eeeeeeee eeeeeeee ee 888 °M.[‌88‌]

Meeeeeeeeeee Meeeeeeee

8-Meeeeee-8-(eeeeeeeeeeeee)eeeeee (Meeee 8, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

M Meeeeee eeee eee eeeeeee eeee 8-eeeeeeeeeeeee (8.8 eeee), {Me(MMe)(eee)}8 (8.8 ee, 8.88 eeee), eee 8,8′-ee-eeee-eeeee-8,8′-eeeeeeeee (8.8 ee, 8.88 eeee), eee eeee eeeeeeeee eee eeeeeee eeee eeeee (8 ×). Meeee e eeeeeeee eeee ee eeeee, eeeeeeeeee (88 ee, 8.8 eeee) eee eeeee MMM (8 eM) eeee eeeee. Meeee eeeeeeee eee 8 eee, Me8MeM (8; 88 µM, 8.8 eeee) eee eeeee eeeeeeee eee eee eeeeeee eee eeeeee ee 88 °M eee 88 e. Mee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeeee eee); eeeee: 88%; 8M MMM (888 MMe, MMMe8, δ): 8.88–8.88 (e, 8M), 8.88–8.88 (e, 8M), 8.88 (e, 8M), 8.88 (e, 8M), 8.88 (ee, 8M), 8.88 (ee, M = 8.8, 8.8 Me, 8M), 8.88 (e, 8M), 8.88 (e, M = 8.8 Me, 8M); 88M MMM (88 MMe, MMMe8, δ): 8.8, 8.8, 88.8, 888.8, 888.8, 888.8, 888.8, 888.8, 888.8, 888.8, 888.8.

8,8-Meeeeee-8-eeeeee-8,8-eeeeeee-8,8-eeeeeeeeeeeee (88, M8 = M; M8 = Me); Meeeeee Meeeeeeee:[‌88‌]

Me e M8-eeeeee eeeeeeee, eeeeeeeeeeee (88, M8 = M; M8 = Me; ee. 8.8 eeee) eee eeeeeee eeee e eeee eee eeeeeeeee ee MMM (8.88 eM). Mee eeeeeeeee eeee eee eeeeeee eeeee eeee e eeeeeee eeeeeeee eeeee eeee ee {Me(MMe)(eee)}8 (8.8 µeee, 8.88 eee%) ee MMM (8.88 eM) eee eeee eeee eeee Me8MeM8 (8.88 eeee). Mee eeeeeeeee eeee eee eeeeeee ee eee eeeeeeee ee ee eeeee eeeeeeee eeeeeeeeee eeee eee eeeeeeeeeeeee eeeeeee(eeeeeee)eeeee eeeee 88 (M8 = M; M8 = Me) eee eeeeeeee. Mee eeeeeeee eeeeeeeee eeee eeee eeeeeee ee eeeeeee eee eeeeeee eeeeeeee eeeee eeee eeeeee eee 8 e. Mee eeeeeeeeeeee eeeeeee(eeeeeee)eeeee eeeee 88 (M8 = M; M8 = Me) eee eeee eeeeeeeeeeee eeeeeee eeee eeeeeee eeeeeeee eeeee eeeee ee eeeeeeeeee (8.88 eeee) ee MMM (8.8 eM), {MeMMe(eee)}8 (8.8 µeee, 8.88 eee%) ee MMM (8.88 eM), eee 8,88-eeeeeeeeeeeeee (88.8 µeee, 8.88 eee%) ee MMM (8.88 eM). Mee eeee eee eeee eeeeeee eeee eee eeeeeeee eee eeeeee ee 88 °M eee 88 e. Meeeeeeeeeeee ee eee eeeeeee, eeeeeeeeee ee eee eeeeeeeee eeeeeee eeee Meeeee, eee eeeeeeeeeeee ee eeeeeeeeeeeeee (eeeeee eee) eeee e eeeeeeeee eee; eeeee: 888 ee (88%). Meee eee eeeeeeee eee eeeeeeeee ee e 8-eeee eeeee, e eeeee ee 88% eee eeeeeeee; 8M MMM (888 MMe, MMMe8, δ): 8.88–8.88 (e, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (ee, M = 8.8, 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M); 88M MMM (888 MMe, MMMe8, δ): 8.8, 8.8, 8.8, 8.8, 88.8, 88.8, 888.8, 888.8, 888.8, 888.8, 888.8, 888.8.

Meeeeeee[8-eeeeeee-8-(8,8,8,8-eeeeeeeeeee-8,8,8-eeeeeeeeeeee-8-ee)eeeeee]eeeeee (88, M8 = MMe; M8 = M); Meeeeee Meeeeeeee:[‌88‌]

M eeeeeee ee 8-eeeeeeeeeeeeeeeeeeee eeee (88, M8 = MMe; M8 = M; 8.88 eeee) eee 8-(8M-eeeeeee-8-ee)eeeeeee (88; 88.8 ee, 8.88 eeee) ee eeeeeee (8 eM) eee eeeeee eeeee eeeeee eeee e Meee–Meeee eeeeeeeee eee 8 e. Mee eeee eee eeeeeee ee eeee ee ee, eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Me eee eeeeeee eee eeeee MeM8(MM)(MMe8)8 (88.8 ee, 8.888 eeee). Mee eeeee eeee eee eeeeee eeee eeeee M8, eee eeee eeeeeeeeee (888 ee, 8.88 eeee), Me8MeM (8; 888 µM, 8.88 eeee), eeeeeee (88.8 µM; eeeeeeee eeeeeeee), eee eeeeeee (8.88 eM) eeee eeeee eeeee e M8 eeeeeeeeee. Mee eeeeeee eee eeeeee ee 888 °M eee 88 e. Me eee eeeeeee eeee eeeee eeeeeee (88 ee, 8.88 eeee), MeMM•M8M (88 ee, 8.88 eeee), eee MMM (8 eM) ee ee. Meeee eeeeeeee eee 8 e, eee eeeeeee eee eeeeee eeeeeee e eeeee eee ee Meeeeeee (eeeeee/MeMMe 88:8). Mee eeeeeeee eee eeeeeeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeee MMMM (eeeeee, 88 eM · eee−8) ee eeeeee eee eeeeeee ee ee eee; eeeee: 88.8 ee (88%); 8M MMM (888 MMe, MMMe8, δ): 8.88 (e, 88M), 8.88 (e, 88M), 8.88 (e, 8M), 8.88 (ee, M = 8.8, 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M), 8.88 (e, M = 8.8 Me, 8M); 88M MMM (888 MMe, MMMe8, δ): 8.8, 8.8, 88.8, 88.8, 88.8, 888.8, 888.8, 888.8, 888.8, 888.8; 88M MMM (888 MMe, MMMe8, δ): 88.8; MM (eeee) ν̃eee: 8888, 8888, 8888, 8888, 888 ee−8.

References