Synthesis and reaction of 1,4-acetal-bridged 2,3,5,6-tetramethylidene-bicyclo[2.2.0]hexane: the first Diels–Alder route to Dewar benzenes

Abstract

The 1,4-acetal-bridged derivative of hitherto unknown 2,3,5,6-tetramethylidenebicyclo[2.2.0]hexane, which produces the Dewar benzene skeleton through two successive Diels–Alder reactions with dienophiles, has been synthesized in four steps from dimethyl acetylenedicarboxylate and 1,4-dichlorobut-2-ene.