Enantioselective biotransformation of α,α-disubstituted dinitriles to the corresponding 2-cyanoacetamides using Rhodococcus sp. CGMCC 0497
摘要:
A new application of nitrile-converting enzymes in the synthesis of optically active alpha,alpha-disubstituted-alpha-cyanoacetamides from alpha,alpha-disubstituted-malononitriles with whole cells of Rhodococcus sp. CGMCC 0497 is described. The products were obtained with enantiomeric excesses of up to >99%, and yields of up to 53%. They are very useful chiral intermediates especially for the synthesis of chiral alpha,alpha-disubstituted amino acids but have never been synthesized directly by chemical or enzymatic methods. (C) 2003 Elsevier Ltd. All rights reserved.
been developed for the reductive alkylation of malononitrile with aromatic aldehydes. This new procedure has vastly improved the yield and efficiency of the process, and increased the scope of the aromatic aldehydes. Incorporating water as the catalyst in ethanol for the condensation step allows stoichiometric amounts of malononitrile and aldehyde to be employed. The reduction step takes place quickly
report an enantioselective nickel-catalyzed intermolecular [2 + 2 + 2] cycloaddition of alkyne-tethered malononitriles with alkynes for the synthesis of densely substituted pyridines. The α-all-carbon quaternary center adjacent to pyridine is introduced by desymmetrizing the two cyano groups of disubstituted malononitriles. Notably, terminal alkynes are also tolerated with good regioselectivity to afford
Sodium Borohydride as the Only Reagent for the Efficient Reductive Alkylation of Malononitrile with Ketones and Aldehydes
作者:Robert E. Sammelson、Jason C. Dunham、Adam D. Richardson
DOI:10.1055/s-2006-926307
日期:——
malononitriles has been developed. In this method, sodium borohydride in isopropanol has a catalytic effect on the initial condensation between malononitrile and aldehydes or ketones at 0 °C. The sodium borohydride also simultaneously acts as a reagent and reduces the unsaturated intermediate formed in situ by the condensation. This simple reductive alkylation method effectively consumes all malononitrile
condensation–reduction approach, which was carried out in water, has been reported. Using Hantzsch esters as reducing agent, under the promotion of base, a variety of reduced Knoevenagel adducts could be easily prepared by direct alkylation of malononitrile, ethyl 2-cyanoacetate, and 2-(4-nitrophenyl)acetonitrile, respectively. Meanwhile, a gram-scale synthesis of the protocol was also realized with excellent
THE REACTIONS OF BENZYLIDENEMALONONITRILES AND β-NITROSTYRENES WITH<i>O</i>-PHENYLENEDIAMINE INCLUDING THE NEW ORGANIC REDOX REACTIONS BETWEEN THE OLEFINS AND 2-PHENYLBENZIMIDAZOLINES
The reactions of benzylidenemalononitriles and β-nitrostyrenes with o-phenylenediamine in ethanol at boiling temperature gave the reduced products of the olefins. The reactions were rationalized on the basis of the role of 2-phenylbenzimidazolines as a hydrogen donor.