ENE REACTIONS OF DIALKYL DIOXOSUCCINATE ESTERS

The ene reactions of dimethyl dioxosuccinate (1) and of diethyl dioxosuccinate (2) with olefins give the expected addition products. The reactions of 1 with vinyl ethers or an eneamine provide the cyclopentenones 15 and 16 in a sequence which is consistent with an ene reaction followed by a cyclization. The tin tetrachloride catalyzed conversion of 6 to 17 provides an example of a formal type II ene reaction to give a cyclopentyl ring. However, the stereochemistry of 17 suggests the reaction involves a stepwise ionic process.