No abstract

N-Tosyl-(S a )-binam-L-prolinamide is an efficient catalyst for the aqueous aldol reaction, between glyoxylic acid, as monohydrate or aqueous solution, and ketones. This reaction led to the formation of chiral a-hydroxy-g-keto carboxylic acids in high levels of diastereoand enantioselectivities achieving mainly anti aldol products.

Aqueous Enantioselective Aldol Reaction of Methyl-and Phenylglyoxal Organocatalyzed by N-Tosyl-(S a)-binam-L-prolinamide. -Chiral -oxo--hydroxycarbonyl compounds and -oxo--hydroxy-,-unsaturated esters are synthesized by aldol reactions of methylglyoxal (I) under aqueous conditions or phenylglyoxal monohydrate with ketones or aldehydes. -(MOLES, F. J. N.; GUILLENA, G.; NAJERA*, C.; Synlett 26 (2015) 5, 656-660, http://dx.doi.org/10.1055/s-0034-1379969 ; Dep. Quim. Org., Univ. Alicante, E-03080 Alicante, Spain; Eng.) -H. Toeppel 30-032

N-Tosyl-(S a)-binam-L-prolinamide is an efficient catalyst for the aqueous aldol reaction between ketones and glyoxylic acid, as the monohydrate or as an aqueous solution, or a 50% toluene solution of ethyl glyoxylate. These reactions led to the formation of chiral α-hydroxy-γ-keto carboxylic acids and esters in high levels of diastereo-and enantioselectivities (up to 97% ee), providing mainly anti aldol products. Only cyclopentanone and cyclohexane-1,4-dione afforded an almost 1:1 mixture of the syn/anti-diastereoisomers; however, the reaction between 4-phenylcyclohexanone and ethyl glyoxylate gave the corresponding syn,syn-product as the major diastereoisomer.

Abstract:The direct aldol reaction between methylglyoxal (40% aqueous solution) or phenylglyoxal monohydrate and ketones or aldehydes is catalyzed by Ntosyl-(Sa)-binam-L-prolinamide to afford the corresponding chiral γ-oxo-β-hydroxy carbonyl compounds, mainly as anti isomers with enantioselectivities up to 97%. Georg