Preparation of Functional Benzofurans, Benzothiophenes, and Indoles Using Ester, Thioester, and Amide via Intramolecular Wittig Reactions

Preparation of new types of highly functional benzofurans, benzothiophenes, and indoles is realized via intramolecular Wittig reactions with the corresponding ester, thioester, and amide functionalities. The key intermediates, phosphorus ylides, presumably result from the addition of Bu3P toward aldehydes followed by acylation and deprotonation. Synthesis of functional benzofurans directly starting from salicylic aldehyde derivatives with acid chlorides in a one-step procedure is also developed.