One-Pot Absolute Stereochemical Identification of Alcohols via Guanidinium Sulfate Crystallization
作者:Beau R. Brummel、Kinsey G. Lee、Colin D. McMillen、Joseph W. Kolis、Daniel C. Whitehead
DOI:10.1021/acs.orglett.9b03792
日期:2019.12.6
A novel technique for the absolute stereochemicaldetermination of alcohols has been developed that uses crystallization of guanidinium salts of organosulfates. The simple one-pot, two-step process leverages facile formation of guandinium organosulfate single crystals for the straightforward determination of the absolute stereochemistry of enantiopure alcohols by means of X-ray crystallography. The
Dynamic kinetic asymmetric transformation of 1,4-diols and the preparation of trans-2,5-disubstituted pyrrolidines
作者:Linnéa Borén、Karin Leijondahl、Jan-E. Bäckvall
DOI:10.1016/j.tetlet.2009.02.079
日期:2009.7
Dynamic kinetic asymmetric transformation (DYKAT) of a series of 1,4-diols is carried out with Candida antarctica lipase B (CALB), Pseudomonas cepacia lipase II (PS-C II), and a ruthenium catalyst. A β-chloro-substituted 1,4-diol is successfully transformed into an optically pure 1,4-diacetate, which is a highly useful synthetic intermediate. The usefulness of the optically pure 1,4-diacetates is demonstrated
synthetic route to C2-symmetric chiral 1,4-diols based on the borane-mediated oxazaborolidine-catalysed reduction of 2-ene-1,4-diones (2), of 2-yne-1,4-diones (3), and/or of Co-complexed diketones 4 is described. Good to excellent enantio- and diastereoselectivities have been obtained in the reduction of diketones 3 and 4, catalysed by oxazaborolidines 6 and 5, respectively.
An efficient method for the preparation of C2-symmetric, chiral alk-2-ene-1,4-diols (4) has been achieved, based on the borane-mediated reduction of symmetric alk-2-ene-1,4-diones (2) in the presence of oxazaborolidine (R)-1. In general, the presence of the double bond in 2 has been beneficial (compared with the related saturated 1,4-diketones 3) not only as far as the stereoselectivity in the reduction
New chiral 1,1′-bis(phospholano)ferrocene ligands for asymmetric catalysis
作者:Mark J. Burk、Michael F. Gross
DOI:10.1016/s0040-4039(00)78543-1
日期:1994.12
The synthesis of two new 1,1′-bis(phospholano)ferroceneligands are described. Preliminary catalytic studies showed that enantioselectivities as high as 83% ee could be achieved in the hydrogenation of several model olefin, ketone, and hydrazone substrates.