Cobalt-Catalyzed Cyclization/Hydrosilylation Reaction of 1,6-Diynes Enabled by an Oxidative Cyclization–Hydrosilylation Mechanism

• Published in: ACS catalysis Vol. 14; no. 6; pp. 4001 - 4007
• Main Authors: Dong, Jiaxing, Leng, Xuebing, Wang, Dongyang, Deng, Liang
• Format: Journal Article
• Language: English
• Published: American Chemical Society 15.03.2024
• Subjects: N-heterocyclic carbene; hydrosilylation; cobalt; alkyne; cyclization
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.4c00473

Transition-metal-catalyzed cyclization/hydrosilylation of 1,6-diynes is a useful method for the preparation of five-membered ring-fused silyl dienes that are useful reagents in organic synthesis. Only a handful of noble metal catalysts facilitating this transformation are known, and nonprecious metal catalysts effecting the reaction have remained elusive. Herein, we report that low-coordinate Co(0)-N-heterocyclic carbene complexes can catalyze the cyclization/hydrosilylation of 1,6-diynes with tertiary and secondary hydrosilanes, furnishing five-membered ring-fused (Z)-1-silyldienes in good yields and excellent stereoselectivity. Mechanistic study disclosed that the catalytic cycle likely has oxidative cyclization of 1,6-diynes with Co(0) species as the key step. This mechanism accounts for the high stereoselectivity and absence of uncyclized hydrosilylation byproducts in the cobalt-catalyzed cyclization/hydrosilylation reaction, which is different from the hydrosilylation-cyclization mechanism of the noble metal-catalyzed reactions.