Highly enantioselective synthesis of long chain alkyl trifluoromethyl carbinols and β-thiotrifluoromethyl carbinols through lipases
摘要:
Among a variety of lipases tested, Candida antarctica lipase has been found to promote the enantioselective acylation of long chain alkyl trifluoromethyl carbinols 1a-4a and beta-thiotrifluoromethyl carbinols 5a-7a, producing both R and S enantiomeric alcohols in good to excellent chemical yield and enantioselectivity. In all cases the lipase preferentially acylates the S enantiomer, irrespective the presence or not of a sulfur atom in beta position to the hydroxyl group, When the reaction was carried out on the non-fluorinated substrates 1c-2c, the process occurred much faster and with higher e.e. of the less reacting enantiomer than when conducted on the fluorinated substrates. Copyright (C) 1996 Elsevier Science Ltd
Efficient Synthesis of Optically Pure 1,1,1-Trifluoro-2-alkanols through Lipase-Catalyzed Acylation in Organic Media
摘要:
Lipase-catalyzed esterification was successfully utilized for the optical resolution of 1,1,1-trifluoro-2-alkanol 1 when racemic 1 was treated with lipase from Candida antarctica in hexane in the presence of molecular sieves (4 Angstrom) to provide the corresponding (S)-acetate 2 in an optically pure state. Alkanol 1 is known as an important component of liquid crystal compounds which display remarkable ferroelectric liquid crystal (FLC) characteristics. Five types of optically pure alkanols, i.e., 1,1,1-trifluoro-2-octanol (1a), 1,1,1-trifluoro-2-nonanol (1b), 1,1,1-trifluoro-2-decanol (1c), 1,1,1-trifluoro-2-undecanol (1d), and 1,1,1-trifluoro-8-(benzyloxy)-2-octanol (1e), were thus obtained by the lipase-catalyzed acylation.
The highly enantioselectivesynthesis of 1,1,1-trifluoroalkan-2-ols has been achieved by hydrogenating 1,1,1-trifluoroalkan-2-one enol acetates in the presence of chiral ruthenium catalysts. An enol acetate, 2-acetoxy-3,3,3-trifluoro-1-(phenylthio)propene, can be successfully transformed into enantiomerically pure trifluorolactic acid.