THE DIELS-ALDER CYCLOADDITION REACTION OF SOME SUBSTITUTED FURANS ANDE-1,2-BIS(PHENYLSULFONYL)ETHYLENE

The Diels-Alder cycloaddition between several 2-, and 3-substituted fu rans and E-1,2-bis(phenylsulfonyl)ethylene have been carried out in hi gh yields. Stereoselectivity observed in the case of 2-sustituted fura ns has been explained by means of the MM3-transition state model. The model had to be refined for 2-methoxyfuran due to the asymmetry induce d over the transition state geometry by the electron-donating methoxyl group. Selectivity in 2-substituted furans arose by interactions betw een the 2-substituent and the sulfonyl groups (steric repulsion with t he cis-sulfonyl or long-range favourable interactions with the trans-s ulfonyl). (C) 1998 Elsevier Science Ltd. All rights reserved.