Diels-Alder reactions of enantiopure [(1S)-isoborneol-10-sulfinyl]- and [(1S-exo)-2-bornylsulfinyl]vinylcyclohexenes with maleimides

Article abstract of DOI:10.1016/S0957-4166(99)00409-7

Uncatalyzed cycloadditions of enantiopure [(1S)-isoborneol-10-sulfinyl]- and [(1S-exo)-2-bornylsulfinyl]vinylcyclohexenes with N-phenylmaleimide occur with good facial diastereoselectivity, controlled by the sulfur configuration, even if the extent of this stereoselection appears influenced by the structural features of the terpene residue directly linked to the sulfoxide moiety. Complete endo diastereoselectivity is observed in LiClO₄ catalyzed cycloadditions of (R(S))-1-{1-[(1S)-isoborneol-10-sulfinyl]- and (S(S))-1-{1-[(1S-exo)-2-bornylsulfinyl]vinyl}cyclohexenes 4 and 5, respectively. The Diels-Alder reactivity of 5 and (S(S),E)-1-{2-[(1S-exo)-2- bornylsulfinyl]vinyl}cyclohexene 7, with the chiral auxiliary being in a different position with respect to the diene moiety, is also compared, and the results obtained confirm that 1-sulfinyldienes are less reactive than 2- sulfinyldienes. SnCl₄ catalyzed cycloaddition of 7 with N-methylmaleimide is also performed.