(R)-(+)-Binol-functionalized mesoporous organosilica as a highly efficient pre-chiral catalyst for asymmetric catalysis.
(R)-(+)-Binol-functionalized chiral periodic mesoporous organosilicas (PMOs) with different framework compositions were successfully synthesized by cocondensation of (R)-2,2'-di(methoxymethyl)oxy-6,6'-di(1-propyltrimethoxysilyl)-1,1'-binaphthyl (BSBinol) with 1,2-bis(trimethoxysilyl)ethane (BTME) and tetramethoxysilane (TMOS) using triblock copolymer P123 as a template in acidic solution. The mixture of BTME and BSBinol can result in a highly ordered mesostructure in an acidic medium but the mesoporous materials synthesized using a mixture of TMOS and BSBinol can only be obtained in a weak acidic buffer solution. All the materials are efficient catalysts (coordinated with Ti) for asymmetric addition of diethylzinc to aldehydes. The chiral PMO with ethane and (R)-(+)-Binol in the framework exhibits an enantioselectivity as high as 90% with a turnover frequency (TOF) of 104 h(-1), which is even higher than the homogeneous (R)-(+)-Binol catalyst (83% ee with TOF of 96 h(-1)) using toluene as solvent under similar conditions. This work demonstrates the positive effect of the rigid pore wall in increasing the enantioselectivity of the chiral PMOs.
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Institution, 457 Zhongshan Road, Dalian 116023, China.
Xiao
X
Liu
Peiyuan
P
Wang
Yan
Y
Yang
Peng
P
Wang
Qihua
Q
Yang
D000447:Aldehydes / Q000737:chemistry; D002384:Catalysis; D004980:Ethane / Q000031:analogs & derivatives / Q000737:chemistry; D009281:Naphthalenes / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry; D016062:Porosity; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D014297:Trimethylsilyl Compounds / Q000737:chemistry
D000447:Aldehydes; D009281:Naphthalenes; D009942:Organometallic Compounds; C475744:S(-)2,2'-dihydroxy-1,1'-binaphthyl; D012821:Silanes; D012997:Solvents; D014297:Trimethylsilyl Compounds; C517344:bis(trimethoxysilyl)ethane; C061205:tetramethoxysilane; D012822:Silicon Dioxide; D004980:Ethane; C454811:diethylzinc