Stille Coupling Involving Bulky Groups Feasible with Gold Cocatalyst

摘要

There is a growing interest in bimetallic catalysis, a synthetic approach combining two or more non-main-group-metal catalysts working in tandem. A main-group metal is often involved as the nucleophilic reagent. The aim of bimetallic catalysis is to take advantage of the specific behavior of each catalyst in new one-pot synthetic routes. For the Au/Pd couple it is known that the Au/Pd transmetalation, a step which is hoped to connect the palladium and the gold catalytic cycles, is kinetically feasible,even for fairly bulky groups. However, so far only a few Au/Pd bimetallic catalyzed processes have been reported, including the Sonogashira-like cross-coupling, the carbometallation of alkynes, and processes combining cyclization with cross-coupling steps. Herein we examine the potential of the Au/Pd pair in a Stille reaction, where tin is the third metal involved in the system, thus providing the nucleophile.