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).
Arjona, O., Iradier, F., Mañas, R. M., Plumet, J., Grabuleda, X., & Jaime, C. (1998). The diels-alder cycloaddition reaction of some substituted furans and E- 1,2-bis(phenylsulfonyl)ethylene. Tetrahedron, 54(31), 9095-9110. https://doi.org/10.1016/S0040-4020(98)00547-X