STEREOSELECTIVE CONTROL IN 1,3-DIPOLAR CYCLOADDITION OF NITRONES TO SUBSTITUTED STYRENES

The stereochemistry of 1,3-dipolar cycloaddition of C-methyl-N-phenyln itrone I with substituted styrenes has been investigated. The presence of an hydroxyl function at the ortho position Lt the dipolarophile co mpletely controls the stereochemical course of the reaction with the e xclusive formation of cycloadduct 7. MNDO calculations help to rationa lise the obtained results on the basis of an intermolecular hydrogen b onding, which leads to changes irt the FMO properties so improving a s tabilizing secondary orbital interaction in the E-endo transition star e leading to cis isomer.