Stereoselective control in 1,3-dipolar cycloaddition of nitrones to substituted styrenes

Article abstract of DOI:10.1016/S0040-4020(01)89695-2

The stereochemistry of 1,3-dipolar cycloaddition of C-methyl-N-phenylnitrone 1 with substituted styrenes has been investigated. The presence of an hydroxyl function at the ortho position in the dipolarophile completely controls the stereochemical course of the reaction with the exclusive formation of cis cycloadduct 7. MNDO calculations help to rationalise the obtained results on the basis of an intermolecular hydrogen bonding, which leads to changes in the FMO properties so improving a stabilizing secondary orbital interaction in the E-endo transition state leading to cis isomer.