摘要:

Because of the high reactivity of Grignard reagents a direct highly enantioselective Grignard reaction with aldehydes has lately been disclosed In this report. Grignard leagents were: introduced with bis[2-(N,N'-dimethylamino)ethyl) ether (BDMAEF) to effectively deactivate then reactivity thus a highly enantioselective alkylation of aldehydes with Grignard reagents resulted from catalysis by (S)-BINOL-Ti(O'Pt)(2). It is thought that BDMAEE chelates the in situ generated salts MgBt(2) from Schlenk equilibrium of RMgBr and Mg(O'Pt)Br from transmetalation of RMgBt with Ti(O'Pt). The Mg salt can actively promote the undesired background reaction to give the racemate I he chelation definitely inhibits the catalytic activity of the Mg salts suppresses the unwanted background reaction, and enables the highly enantioselective addition catalyzed by (S)-BINOL-Ti(O'Pt)(2) Consequently, the Mg salt byproducts were not removed. less Ti(O'Pt)(4) than RMgBr was used. and extremely low temperature was avoided in this catalytic asymmetric reaction in comparison with the research disclosed before Various alkyl Grignard leagents were investigated in the asymmetric addition and 'BuMgBr resulted in the highest enantioselectivity. >99% Furthermore important intermediate secondary arylpropanols for chiral drug synthesis were effectively synthesized with high enantioselectivity, up to 97%, in one step

附注:

659YZTimes Cited:24Cited References Count:105