Asymmetric diastereoselective thia-hetero-Diels-Alder reactions of dithio esters

International audienceAsym. thia-Diels-Alder reactions involving new dithio esters bearing a chiral auxiliary are described, with diastereoselectivities up to 78%. Double-stereodifferentiating expts. employing chiral substrates in the presence of a chiral Lewis acid catalyst have been also carried out and, in this case, a diastereomeric excess of 90% was reached. The abs. stereochem. of cycloadducts resulting from dithiooxalates and carbonyloxazolidinone dithio esters was assigned based on an X-ray structure and chem. correlation. In order to rationalize the sense of the chiral induction, stereochem. models for Cu(II)/bis(oxazoline)/dithioester complexes are proposed