STEREOSELECTIVE RADICAL-MEDIATED CYCLIZATION OF NOREPHEDRINE DERIVED O-BROMOBENZAMIDES - ENANTIOSELECTIVE SYNTHESIS OF 4-SUBSTITUTED 1,2,3,4-TETRAHYDROISOQUINOLINES

Radical-mediated cyclization of norephedrine derived o-bromobenzamide 5 was found to be fairly stereoselective (85:15)favouring diastereoisomer trans-6. Tricyclic delta-lactams 6 were transformed in high yield into enantiomerically enriched (R)-1,2,3,4-tetrahydro-2,4-dimethylisoquinoline 8. Transition state modelling with a force field developed ad hoc (see also: Belvisi, L. et al. Tetrahedron 1992, 48, 3945) nicely predicts the stereochemical results.