Reactivity of chiral exocyclic N-acyliminium ions with aromatic derivatives
摘要:
Chiral N-acyliminium ions obtained from optically active N-[1-(phenylsulfonyl)alkyl]oxazolidin-2-ones at low temperature in the presence of titanium tetrachloride react with electron-rich aromatic compounds to afford the corresponding adducts in good yields and variable diastereoselectivities. Chemoselective cleavage of the oxazolidin-2-one ring with lithium/ammonia affords the corresponding benzylamines in enantioenriched form. The utilization of 4-benzyloxazolidin-2-one as a chiral auxiliary leads to intramolecular cyclization with exclusive formation of one diastereomer. The obtained tricyclic derivatives possess the core structure of some aza analogs of the anticancer drug podophyllotoxin. (C) 2003 Elsevier Science Ltd. All rights reserved.