Single and double asymmetric induction in Diels-Alder cycloadditions with chiral acylnitroso dienophiles

Article abstract of DOI:10.1016/S0957-4166(00)80021-X

Diels-Alder reaction of the achiral 1-silyloxybutadiene 1a with the chiral acylnitroso dienophile 2a gave cycloadduct 4 in high diastereomeric excess (d.e. > 98%), a result which is undoubtedly due to the C-2 symmetrical chiral dimethylpyrrolidine inductor. Excellent d.e. was also observed when the (R)-prolinol dienophile 2d was reacted with the chiral diene 1b (d.e. = 96%), whereas cycloaddition of the (S) enantiomer 2e with 1b gave only poor asymmetric induction (d.e. = 4%). These two latter examples nicely illustrate the influence of 'matched pair' (1b/2d) versus 'mismatched pair' (1b/2e) upon double asymmetric induction. All herein reported Diels-Alder cycloadditions were regiospecific.