An asymmetric route to the 5,6-dihydro-4H-1,3-thiazine skeleton via an asymmetric hetero Diels-Alder reaction

Article abstract of DOI:10.1016/0957-4166(95)00087-6

Magnesium bromide mediated hetero Diels-Alder cycloaddition of diene 1 (R¹ = Ph) to chiral N-acryloyl-2-oxazolidinone 4b leads to 5b as the sole adduct formed. Chiral auxiliary removal leads to enantiomerically pure 5,6-dihydro-4H-1,3-thiazine 3 (R² = Bn). The selectivity of the cycloaddition is reversed under thermal or high pressure activation. The predominant diastereomeric adduct 6b is isolated in pure form after flash chromatography.