Chiral N-heterocyclic carbene catalyzed staudinger reaction of ketenes with imines: highly enantioselective synthesis of N-Boc beta-lactams.
N-heterocyclic carbenes (NHCs) were demonstrated to be efficient catalysts for the Staudinger reaction of ketenes with N-tosyl, N-benzyloxycarbonyl, or N-tert-butoxycarbonyl imines. Chiral NHC 8b, conveniently prepared from L-pyroglutamic acid, catalyzed the reactions of arylalkylketenes with a variety of N-tert-butoxycarbonyl arylimines to give the corresponding cis-beta-lactams in good yields with good diastereoselectivities and excellent enantioselectivities (up to 99% ee). Two possible catalytic pathways, initiated by the addition of NHC to ketenes or imines, were discussed.
Zhang
Yan-Rong
YR
Beijing National Laboratory for Molecular Sciences, Laboratory of Chemical Biology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
He
Lin
L
Wu
Xu
X
Shao
Pan-Lin
PL
Ye
Song
S
D002384:Catalysis; D005030:Ethylenes / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D047090:beta-Lactams / Q000138:chemical synthesis* / Q000737:chemistry*
D005030:Ethylenes; D007097:Imines; D007659:Ketones; D047090:beta-Lactams; C008223:ketene