An Interesting Rearrangement in the Cycloaddition of 1-(Methoxycarbony)Cyclopentadiene¹

Abstract

An attempted Diels-Alder reaction of 1-methoxycarbonylcyclopentadiene with cis-1,2-bis(phenylsulfonyl)ethylene gives a mixture of two sulfones, neither of which is the desired adduct. Instead a [1.5] sigmatropic rearrangement of the 1-methoxycarbonylcyclo-pentadiene precedes the 4 + 2 cycloaddition. Subsequent desulfonation also occurs in an unusual manner.