Asymmetric Acid-Catalyzed Meerwein−Ponndorf−Verley−Aldol Reactions of Enolizable Aldehydes

Abstract

A highly, stereo- and regioselective Meerwein-Ponndorf-Verley-Aldol etherification process of enolizable aldehydes is described. This new transformation is catalyzed by trifluoroacetic acid. The method also allows cross-aldol reactions with alpha-branched enolizable aldehydes and thus provides access to defined configured quaternary stereogenic centers.

Efficient Organocatalytic Cross-Aldol Reaction between Aliphatic Aldehydes through Their Functional Differentiation

“…The aldol reaction has long been recognized as one of the most fundamental tools for the construction of new carbon–carbon bonds . In this area, the cross-aldol reaction between two different aldehydes has remained an elusive challenge because of undesired side reactions including homoaldol reaction and multiple addition of nucleophilic species such as the enolate and the enamine to the aldol product. − …”

Investigation of Various Organocatalysts for Improved and Efficient One Pot Synthesis of 2,3-Dihydro-1H-1,5-benzodiazepines Under Solvent-Free Condition

“…The synthetic approach is outlined in (Scheme-I). Various aliphatic and aromatic acids have been used to catalyze the synthesis of 1,5-benzodiazepines, out of which trifluoroacetic acid (TFA) came out to be the most effective catalyst under solvent-free condition ( Recently, trifluoroacetic acid has emerged as a promising catalyst for the synthesis of wide variety of reactions such as Paal-Knorr Furan Synthesis 15 , Meerwein-Ponndorf-Verley-Aldol reactions of enolizable aldehydes 16 , Pictet-Spengler reaction 17 , Claisen rearrangement 18 and cross-coupling reactions 19,20 . Trifluoroacetic acid is the simplest stable perfluorinated carboxylic acid chemical compound, with the formula CF3CO2H.…”