Catalysis of ene reactions by lithium perchlorate

Abstract

The ene reaction of some allylic hydrocarbons, and the metallo-ene reaction of some allyltin compounds, with 1,3,4-triazoline-2,5-diones or with diethyl azodicarboxylate as enophiles, in diethyl ether are strongly catalysed by lithium perchlorate. Azobenzene, on the other hand, reacts slowly with alkyltin compounds, undergoing hydrostannation. The reaction of cholesterol or of tributylallyltin with singlet oxygen is subject to a smaller catalysis.