Synergistic Palladium/Lewis Acid‐Catalyzed Regio‐ and Stereo‐divergent Bissilylation of Alkynoates: Scope, Mechanism, and Origin of Selectivity

• Published in: Angewandte Chemie International Edition 2023-09, Vol.62 (37), p.e202309169-n/a
• Main Authors: Zhao, Shuang, Ding, Linlin, Sun, Yingman, Wang, Minyan, Zhao, Dongbing
• Format: Article
• Language: English
• Subjects: Alkenes; Alkynes; Alkynoates; Bioactive compounds; Biological activity; Bissilylation; Chemical reactions; DFT Calculation; Divergence; Divergent Selectivities; Intermediates; Lewis acid; Palladium; Pd Catalysis; Quinoline; Reaction mechanisms; Reagents; Regioselectivity; Steric effects; Transition metals
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202309169

Transition metal‐catalyzed bissilylation reactions of alkynes with disilane reagents have become one of the most straightforward and efficient protocols to rapidly produce structurally diverse alkenyl silicon derivatives. In these reactions, the utilization of unsymmetrical disilane reagents provided the possibilities for reactivity enhancement as well as the synthetic merits in contrast to symmetrical disilane reagents. However, a major yet challenging objective is achieving precise control over the selectivity including the regioselectivity and the cis/trans‐selectivity. Herein we realized the first divergent bissilylation of alkynoates with our developed air‐stable disilane reagent 8‐(2‐substituted‐1,1,2,2‐tetramethyldisilanyl)quinoline (TMDQ) by means of synergistic Pd/Lewis acid catalytic system. The catalytic system precisely dictates the selectivity, resulting in the divergent synthesis of 1,2‐bissilyl alkenes. The power of these 1,2‐bissilyl alkenes serving as the key synthetic intermediates has been clearly demonstrated by rapid construction of diverse motifs and densely functionalized biologically active compounds. In addition, the origins of the switchable selectivities were well elucidated by experimental and computational studies on the reaction mechanism and were mainly attributed to different ligand steric effects, the use of the specific disilane reagent TMDQ and the different coordination modes of different Lewis acid with alkynoates. A Pd‐catalyzed divergent bissilylation of alkynoates using disilane reagent TMDQ (see TOC graphic) is presented. Reversed regio‐ and stereo‐selectivity was obtained through addition of Lewis acids. MAD (methylaluminum bis(2,6‐di‐t‐butyl‐4‐methylphenoxide) impacted electronically‐favored migratory insertion through steric effect while the addition of BCF (tris(pentafluorophenyl)borane) allowed reductive elimination as the rate‐determining step.