A route to dihydro[2]benzooxepino[4,5-c]pyridines and dihydrothieno[d][2]benzooxepines via the 1.7-electrocyclisation of carbonyl ylides

Abstract

The cyclisation of diene-conjugated carbonyl ylides of the general type 2, in which the α,β; γ,δ diene function is formed by a benzene ring and either a thiophene or pyridine ring provides a new route to some hetero-fused dihydrobenzooxepines. The oxirane precursors for the carbonyl ylides were synthesised in a two-step scheme from readily available reactants.