The diels-alder cycloaddition reaction of some substituted furans and E- 1,2-bis(phenylsulfonyl)ethylene

The Diels-Alder cycloaddition between several 2-, and 3-substituted furans and E-1,2-bis(phenylsulfonyl)ethylene have been carried out in high yields. Stereoselectivity observed in the case of 2-sustituted furans has been explained by means of the MM3-transition state model. The model had to be refined for 2-methoxyfuran due to the asymmetry induced over the transition state geometry by the electron-donating methoxyl group. Selectivity in 2-substituted furans arose by interactions between the 2- substituent and the sulfonyl groups (steric repulsion with the cis-sulfonyl or long-range favourable interactions with the trans-sulfonyl).