4-Phenyloxazolidin-2-ones and isoindolin-1-ones: chiral auxiliaries for Diels–Alder reactions of N-substituted 1,3-dienes

Terminally N-substituted dienes derived from 3-methylisoindolin-1-one, 4-isopropyl- and 4-phenyloxazolidin-2-one undergo Diels–Alder reaction with a range of activated dienophiles. The reactions reported are completely regio- and endo-selective, with the diastereoisomeric excess with respect to the auxiliary good to excellent in most of the cases reported. A model has been developed for rationalising the stereochemical outcome of these reactions.