Thermal cycloaddition reactions of azulene-1,5-quinones and azulene-1,7-quinones with cyclic dienes and cycloheptatriene

Abstract

[2+4]-[6+4] Cycloadducts were obtained from the thermal cycloaddition reactions of azulenequinones with cyclic 4π systems such as 1,3-diphenylisobenzofuran and isobenzofuran while the reaction of cycloheptatriene and azulenequinones gave ene products as well as cage molecules. The first addition site of 1,3-diphenylisobenzofuran was different for 3-bromoazulene-1,5-quinone and azulene-1,5-quinone; the former reacted on the cyclopentenone part and the latter on the C-6–C-7 bond to avoid formation of an unstable cyclopentadienone structure.