Lm. Harwood et al., STUDIES ON LEWIS-ACID CATALYZED GENERATION AND INTERMOLECULAR TRAPPING OF CHIRAL STABILIZED AZOMETHINE YLIDS, Synlett, (10), 1993, pp. 777-780
Preparation of the ylid (2) derived from 5(R)-phenylmorpholinone (1) i
n the presence of freshly prepared MgBr2.Et2O and dipolarophiles can l
ead to improved cycloaddition yields, with inverse diastereo- and regi
oselection compared to the corresponding uncatalysed reactions.