Direct Allylic C?H Alkylation of Enol Silyl Ethers Enabled by Photoredox-Bronsted Base Hybrid Catalysis

摘要

Enol silyl ethers and their analogues are one of the most versatile substrate classes and enjoy widespread applications in organic synthesis. They can be prepared from parent carbonyl compounds of all oxidation states, such as aldehydes, ketones, esters, and amides, by reliable protocols and exert preeminent reactivity as enolate anion equivalents amenable to various catalysis manifolds. These distinct features render enol sily ethers attractive yet powerful handles for selective α-functionalization of a wide array of carbonyl entities. Based on this general understanding, we envisioned that if the regioselective bond-forming reaction at the inherently inert position could proceed with preservation of the enol silyl ether component, the following transformation at usual active position allows the rapid construction of complex molecular architecture. Here we disclose the direct allylic C?H alkylation of enol silyl ethers with electron-deficient olefins under the hybrid catalysis of iridium-based photocatalyst and pyridine-derived Bronsted base with the irradiation of visible light.