Reaction of chlorosulphonyl isocyanate with 1,3-dienes. Control of 1,2- and 1,4-addition pathways and the synthesis of aza- and oxa-bicyclic systems

Abstract

Cyclopenta-, cyclohexa-, cyclohepta- and cyclo-octa-1,3-dienes react with chlorosulphonyl isocyanate to yield, in each case, a single N-chlorosulphonyl β-lactam as the primary product. In the first three examples, these 1,2-adducts undergo stepwise thermal rearrangements with varying degrees of ease to thermodynamically more stable products of 1,4-addition (cyclisation occurring through O or N in the ambident anion) or substitution products; the β-lactam from cyclo-octadiene could not be induced to rearrange constructively. The reactivity patterns in acyclic dienes are compared and a dipolar reaction mechanism is discussed. Selected n.m.r. spectra are analysed in detail and examples of conversion of the 1,4-adducts into 2-azabicyclo[2.2.1]-heptanes, -heptenes, and -heptadienes and into 2-oxa- or 2-aza-bicyclo[2.2.2]-octanes and -octenes and -bicyclo[3.3.2]nonenes are recorded.