Sequential Cross-Coupling of 1,4-Bissilylbutadienes:Synthesis of Unsymmetrical 1,4-Disubstituted 1,3-Butadienes

摘要

Highly conjugated systems,such as polyenes and aryl polyenes,are a common structural motif in natural products and are also featured prominently in nonlinear optical materials.Traditionally,the synthesis of polyenes relies heavily on stepwise construction of carbon-carbon double bonds independently.However,this approach is tedious and often suffers from poor stereocontrol in setting the alkene geometry.More recently,cross-coupling methods have been employed for the synthesis of a number of polyene natural products in which the key carbon-carbon bond forming step creates the C-C single bond.Highly conjugated systems can be rapidly accessed through double coupling of symmetrical bisstannanes and bisboranes to form symmetrical products.Unsymmetrical products can be prepared through stepwise cross-coupling of l,2-bis(tributylstannyl)ethylene or reagents bearing two different metals.