Application of functionalised 1,3-dipoles to the synthesis of fused heterocycles

Abstract

A general synthetic approach to the formation of fused heterocycles, involving cycloadditions with functionalised 1,3-dipoles and subsequent ring closure, is extended to the systems 6–6, 6–6–5, 6–6–5–5, 6–6–6–5, 6–6–5–6, and 6–5–6. The regiochemistry and stereochemistry of the additions are established by specific deuterium labelling, n.m.r. spectroscopy, and chemical methods. A novel ring transformation of a 2,3-dihydrofuran to a pyridazino[4,5-c]pyridazine is described.