Unprecedented asymmetric induction through configurationally stable lithium N-(α-methylbenzyl)phosphinamides. A new entry to enantiomerically pure γ-aminophosphinic acids and esters
Unprecedented asymmetric induction through configurationally stable lithium N-(α-methylbenzyl)phosphinamides. A new entry to enantiomerically pure γ-aminophosphinic acids and esters
Asymmetric Deprotonation−Substitution of <i>N</i>-Pop-benzylamines Using [RLi/(−)-Sparteine]. Enantioselective Sequential Reactions and Synthesis of N-Heterocycles
Pop-directed asymmetric deprotonation of benzylic amines using [n-BuLi/(-)-sparteine] provides an efficient method for the synthesis of chiral NC alpha and NC alpha,alpha' derivatives with total selectivity with respect to competing allylic and ortho lithiation. The method described herein offers a straightforward route of accessing chiral N-Pop-protected nitrogen heterocycles.
Diastereoselective desymmetrization of diarylphosphinous acid-borane amides under Birch reduction
作者:Marek Stankevič
DOI:10.1039/c4ob02440k
日期:——
Treatment of diarylphosphinous acid-borane amides possessing chiral amido functionality with an alkali metal solution in liquid ammonia induced a preferential dearomatization of one aryl substituent at phosphorus leading to the formation of non-equimolar amounts of diastereomers. Diastereoselectivity of dearomatization depends strongly on the structure of a chiral auxiliary.
Diphenylphosphinamides have been regioselectively ortho-lithiated under mild conditions providing a simple access to ortho-functionalized derivatives in good yields. The application of the methodology to the diastereoselective desymmetrization of the phosphorus atom is described for the first time.
The enantioselective reduction of 1,3-dipolarnitrones to hydroxylamines was achieved by Rh(III)-catalyzed asymmetric hydrogenation and transfer hydrogenation. A wide range of chiral N,N-disubstituted hydroxylamines were synthesized with up to 99 % yield and >99 % ee. Mechanistic investigations and DFT calculations were conducted to elucidate the origin of reactivity and enantioselectivity.