Other Asymmetric and Diastereoselective Aldols

Cinchona-based primary amine catalysis in the asymmetric functionalization of carbonyl compounds has been reviewed and their modularly designed thioamide 0 derivatives have been applied successfully to direct cross-aldol reactions between aldehydes and ketones, reactions of activated carbonyl compounds (isatins) with acetylphosphonate as the enol precursor, and C( 1) functionalization of 1,3-dicarbonyl compounds by aldehydes and ketones. Cross-aldol addition to C(3) of isatins by the methyl group of 4-aryl-tra 5 -cf, -unsaturated methyl ketones has also been promoted 

A fluorous chiral organocatalyst (18) promotes the formation of the anti-Mol product (with up to 96% ee) on reaction between aromatic aldehydes with ketones in brine. The enantioselectivity achieved on promotion of aldol and Mannich reactions by another di-diamine-based catalyst (19) can be reversed by the addition of an achiral acid and is to be the subject of further mechanistic investigation.  

DFT calculations, focusing on the C-C bond forming steps, have been used to rationalize the high regio- and stereo-selectivities found for direct aldol reactions of aliphatic ketones (propanone, butanone, and cyclohexanone) with a chiral primary-tertiary diamine catalyst (trans-N,N-dimethy diaminocyclohexane).  

A chiral bifunctional pyrrolidinylsilanol catalyst is able to direct enantioselective (88% ee) reaction of ethanal with isatin by silanol activation of the electrophile and enantio-control through hydrogen bonding.  

Cross aldehyde reaction between simple ketones has been promoted enantioselectively by chiral l,T-binaphthyl 2,2 -(POPh2) (BINAPO), with SiCl30Tf/i-Pr2NEt.  

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