ENANTIOSELECTIVE DIELS-ALDER REACTIONS - ROOM-TEMPERATURE BIS(OXAZOLINE)-ZINC, BIS(OXAZOLINE)-MAGNESIUM, AND BIS(OXAZOLINE)-COPPER TRIFLATECATALYSTS

A series of chiral bis(oxazoline) ligands, differing in the length of the chain connecting the chiral oxazoline subunits and in the nature o f the substituent at the chiral center, were examined in the room temp erature Zn(OTf)(2), Mg(OTf)(2) and Cu(OTf)(2) catalyzed reaction of N- crotonyloxazolidinone with cyclopentadiene. A 1,4-bis(oxazoline) ligan d proved best for Zn(OTf)(2) and afforded product consistent with reac tion via an octahedral model, while 1,3-bis(oxazoline) ligands were be st for Mg(OTf)(2) and Cu(OTf)(2). (C) 1997 Elsevier Science Ltd.