Simple Syntheses of Seven-Membered Rings via an Entropy/Strain Reduction Strategy

Abstract

The straightforward four-step synthesis of unsaturated seven-membered carbocycles and heterocycles via a route starting from catechols and quinones is described. The route is based on the Perkin ring-closure reaction and was designed to alleviate the usual problems associated with the formation of medium rings. This is achieved through the presence of unsaturation in the starting material, which alleviates ring strain problems, reduces the entropy of activation and ensures that the chain ends are suitably orientated to encourage ring closure.