Z -2-phenyl-4-[(S)- 2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxazolone as the dienophile in asymmetric Diels-Alder reactions

Article abstract of DOI:10.1016/0040-4020(95)00501-X

Diels-Alder reactions of Z-2-phenyl-4-[(S)-2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxazolone and several cyclic and open chain dienes are studied. Less-reactive dienes required longer reaction times and led to isomerization of the Z-oxazolone and isolation of products derived from the E-isomer; Lewis acid catalysts were used to shorten the reaction times. In all cases high diastereofacial selectivity is observed and Diels-Alder adducts can be obtained in high optical purity. The stereochemistry of adducts has been elucidated by single crystal X-ray structure determinations, ¹H-NMR analysis and mechanistic considerations.