The Copper(I) Catalysed [2 + 2] Intramolecular Photoannulation of Carbohydrate Derivatives

Abstract

Carbohydrate derivatives 1a, 1b, 3a and 3b have been subjected to copper(I) catalysed photoannulation to produce tetracyclic products 2a, 2b, 4a and 4b respectively as single enantiomers. The same reaction carried out on substrates 5a and 5b leads stereoselectively to the spiro products 6a and 6b respectively. Photoannulation of substrate 7 gave an approximate 1 : 1 mixture of spiro products 8 and 9. A mechanistic rationalisation of these results is proposed.