Phase transfer catalysis: some recent applications in organic synthesis

A survey dealing with the use of anhydrous potassium carbonate as an effici ent base for promoting organic reactions under solid-liquid phase transfer catalysis (SL-PTC) conditions is reported. In particular, the generation in situ of trifluoro- and trichloroacetamidide, and reactions of these azaani ons with 2-bromocarboxylic esters and epoxides, affording protected alpha-a mino acids and beta-amido alcohols, respectively, are described. The reduct ion of allylic nitroderivatives with CS2 to oximes or nitriles under SL- an d liquid-liquid PTC (LL-PTC) is also presented. Finally, new preparation me thods and a study of the reactivity of quaternary onium fluorides, hydrogen difluorides and dihydrogentrifluorides, together with the use of dihydrogen trifluorides as hydrofluorinating agents under SL-PTC conditions, are repor ted. (C) 1999 Elsevier Science B.V. All rights reserved.