A bifunctional heterogeneous catalyst containing two mutually incompatible acidic and basic sites, which exhibits cooperative catalytic behavior in the aldol condensation of acetone and various aldehydes, was synthesized by postgrafting of 1,5,7- triazabicyclo[4.4.0] dec-5-ene （TBD, a sterically hindered organic base） onto AI-MCM-41 molecular sieve. 2009 Xiao Bing Lu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
A novel unsymmetrical (S,S,S)-salen ligand bearing a derived chiral-BINOL was synthesized by the reaction of the condensation product of (1S,2S)-1,2-diaminocyclohexane mono(hydrogen chloride) with 3-adamanyl-5-tert-butyl-2-hydroxybenzalde-hyde and 3-formoyl-2-hydroxy-2'-alkyloxy-1,1'-binaphthyl,which originated from (S)-1,1'-bi-2-naphthol via a four-step reaction.The cobalt complexes of this ligand,in conjunction with a nucleophilic cocatalyst,exhibited excellent activity in catalyzing asymmetric,regio-and stereo-selective copolymerization of CO2 and racemic propylene oxide.The highest record of kinetic resolution coefficient (Krel) was obtained with the use of binary catalyst system consisting of (S,S,S)-salenCo(III) complex 1c and bulky bis(triphenylphosphine)-iminium chloride (PPNCl).The resulting poly(propylene carbonate)s have more than 99% carbonate linkages and more than 98% head-to-tail content.
REN WeiMin,ZHANG WenZhen & LU XiaoBing State Key Laboratory of Fine Chemicals
