Enantioselective cyanoformylation of aldehydes organocatalyzed by recyclable cinchonidine ammonium salts
作者:Rafael Chinchilla、Carmen Nájera、Francisco J. Ortega、Silvia Tarí
DOI:10.1016/j.tetasy.2009.08.007
日期:2009.10
and α,β-unsaturated aldehydes give lower enantioselectivities (up to 60%) in high yields. The observed sense of the enantioselection was always the same, and the organocatalyst was almost quantitatively recovered by ether-promoted precipitation without any loss of activity. The use of resin-supported cinchonidine-derived ammoniumsalts as an organocatalyst in this transformation was also explored.
Enantioselective and diastereoselective syntheses of cyanohydrin carbonates
作者:Yuri N. Belokon'、William Clegg、Ross W. Harrington、Eisuke Ishibashi、Hiroshi Nomura、Michael North
DOI:10.1016/j.tet.2007.07.016
日期:2007.9
cocatalyst are developed. Under these conditions, two chiral cyanoformates also reacted with aldehydes to give cyanohydrin carbonates. The stereochemistry of this process is predominantly determined by the stereochemistry of the titanium(salen) catalyst and the stereochemistry of two of the cyanohydrin carbonates was confirmed by X-ray crystallography. In a further extension of the chemistry, a homogeneous
Cyanide ion cocatalysis in Ti(salen) catalysed asymmetric cyanohydrin carbonate synthesis
作者:Yuri N. Belokon、Eisuke Ishibashi、Hiroshi Nomura、Michael North
DOI:10.1039/b602156e
日期:——
cocatalyst, 1-2 mol% of titanium(salen) complex catalyses the asymmetric addition of achiral cyanoformates to aldehydes, giving cyanohydrin carbonates with high enantiomeric excesses; and catalyses the diastereoselective addition of chiral cyanoformates derived from alpha-methylbenzyl alcohol to aldehydes, a reaction which exhibits double asymmetric induction.
Enantioselective cyanoformylation of aldehydes using a recyclable dimeric cinchonidine ammonium salt as an organocatalyst
作者:Rafael Chinchilla、Carmen Nájera、Francisco J. Ortega
DOI:10.1016/j.tetasy.2008.01.011
日期:2008.2
ammonium salt is used as a chiral organocatalyst in the enantioselective addition of alkyl cyanoformates to aldehydes in the presence of substoichiometric amounts of triethylamine. Quantitative yields and enantioselectivities up to 88% ee for the corresponding (R)-O-methoxycarbonyl cyanohydrins are obtained using only 1 mol % organocatalyst loading and working at 10 °C. The organocatalyst can be almost
Enantioselective cyanoformylation of aldehydes mediated by BINOLAM–AlCl as a monometallic bifunctional catalyst
作者:Jesús Casas、Alejandro Baeza、José M. Sansano、Carmen Nájera、José M. Saá
DOI:10.1016/s0957-4166(02)00824-8
日期:2003.1
BINOLAM–AlCl's, binaphthoxide aluminium chloride species generated in situ from either (R)- or (S)-3,3′-bis(diethylaminomethyl)-2,2′-dihydroxy-1,1′-binaphthalene (BINOLAM) behave as Lewis acid–Lewis base (LA-LB) catalysts in the enantioselective addition of methyl cyanoformate to aldehydes at room temperature, thereby leading to the asymmetric synthesis of (S)- or (R)-O-methoxycarbonyl cyanohydrins