propargylations occurred under retention of configuration at the propargyliccenter. Most important for the diastereoselectivity of the nucleophilic trapping reaction is the configurational stability of the diastereotopic cation 4 as reflected by substituent effects. In situ ionizations according to an S(N)1-mechanism not only result in a considerable loss but also in an inversion of diastereoselectivity.
addition reactions with eight chiral Li-amide bases, 1 - 8, and five [Cr(arene)(CO)3] complexes, 9 - 13, were investigated. Restriction of conformational freedom in the chiral Li-amide base Li-1, in general, did not result in an increase in asymmetric induction. A new route to enantiomerically enriched (75 - 92%) planarchiral ortho-substituted benzaldehyde complexesvia enantioselective lithiation of
Arenetricarbonylchromium complexes as chiral auxiliaries: asymmetric synthesis of β-lactams
作者:Clara Baldoli、Paola Del Buttero
DOI:10.1039/c39910000982
日期:——
A new enantioselective synthesis of β-lactams via condensation of optically pure ortho-substituted benzylideneaminetricarbonylchromium complexes with ester-enolates is reported; the enantiomeric excess is higher than 98%.
The SmI(2)-induced cross-coupling of Cr(CO)(3)-complexed nitrones with carbonyl compounds is described. This highly chemo- and diastereoselective reaction affords enantiopure [small beta]-amino alcohol complexes in excellent yields.
作者:Arlette Solladié-Cavallo、Jean Suffert、André de Cian
DOI:10.1016/s0022-328x(00)86752-2
日期:1982.9
The photochemical synthesis, spectroscopic properties (IR, 1H NMR, 13C NMR) X-ray structure of some novel chromium(O) dicarbonyl chelates are described.
描述了一些新型的铬(O)二羰基螯合物的光化学合成,光谱性质(IR,1 H NMR,13 C NMR)。