INDOLES VIA PALLADIUM-CATALYZED CYCLIZATION

摘要

The palladium-catalyzed assembly of the functionalized pyrrole nucleus on a benzenoid scaffold is a widely used synthetic tool for the preparation of indole derivatives.This construction can be categorized into four main types: (1) cyclization of alkynes, (2) cyclization of alkenes, (3) cyclization via C-vinyl-ation reactions, and (4) cyclization via N-arylation or N-vinylation reactions. The first approach is by far the most versatile in terms of the range of the added functional groups and of the bonds that can be created in the construction of the pyrrole ring. This method is based on the utilization of precursors containing nitrogen nucleophiles and carbon-carbon triple bonds. The nitrogen nucleophile and alkyne moiety may be part of the same molecule or belong to two different molecules. Some of the most general and versatile alkyne-based cyclizations to indoles are summarized in Fig. 1.