[4π+2π]Cycloadditions of o-Quinones and Symmetrical 6,6-Dialkyl and Cycloalkylfulvenes

Abstract
3,5-Di-tert-butyl-o-benzoquinone on reaction with 6,6-dimethylfulvene furnished the bicyclo[2.2.2]adduct 9 whereas the 6,6-tetramethylenefulvene afforded a novel product 10, which presumably arises by the hetero Diels-Alder reaction of the quinone with the isomerized fulvene. The structure of 10 was confirmed by X-ray crystallography.