The preparations and applications of chiral auxiliaries for asymmetric induction.

摘要

A new C{dollar}sb2{dollar} symmetric secondary amine was prepared. Both enantiomers are readily available in enantiomerically pure form. A lithium amide derived from this chiral amine induced the rearrangement of cyclohexene oxide to cyclohexenol with 17% optical yield. This amine was also used as a chiral auxiliary in the enamine-enal cyclization and a 1:2.3 stereoselectivity was obtained.; A chiral ethylene diamine and {dollar}beta{dollar}-amino alcohols derived from this amine were prepared. They were used as chiral ligands for organometallic reagents in the asymmetric organic reactions. An optical yield of 75% was obtained in the ethylation of benzaldehyde with diethyl zinc in the presence of a chiral {dollar}beta{dollar}-amino alcohol. By contrast, a low optical yield ({dollar}<{dollar}10%) was obtained in the alkylation of aldehydes with organolithium and organomagnesium reagents mediated with a chiral ethylene diamine and in the dihydroxylation of olefins with OsO{dollar}sb4{dollar} and in the reduction of ketones with borane in the presence of these chiral ligands. Chiral compounds derived from this amine with a large dipole moment or similar steric features were prepared for the purpose of molecular structure and crystal packing study.; New analogues of trans-2-phenylcyclohexanol with different electronic and steric aromatic systems were prepared. Ene reaction of alkenes with glyoxylate esters and N-sulfinylcarbamate esters derived from these analogues were studied. A dramatic decrease of stereoselectivity was presumably due to the electronic effect of the aromatic system. A new application of trans-2-phenylcyclohexanol as a chiral auxiliary in the asymmetric allylic amination was demonstrated and a 4:1 diastereoselectivity was obtained in the case of trans-2-octene.