Investigation of the Appel reaction with bromotrichloromethane-triphenylphosphine (CBrCl3/PPh3)

Abstract

Abstract:The Appel reaction of an alcohol with CCl4/PPh3 and with CBr4/PPh3 produce alkyl chlorides and alkyl bromides, respectively. It was found that in the case of using BrCCl3-PPh3, a mixture of alkyl chlorides and alkyl bromides are formed. Dichloromethane (CH2Cl2) and acetonitrile (CH3CN) were used as solvents, where the reaction was found to be solvent-dependent.

Use of Triphenylphosphine-Bromotrichloromethane (PPh3-BrCCl3) in the Preparation of Acylhydrazines, N-Methylamides, Anilides and N-Arylmaleimides From Carboxylic Acids

“…This includes the dehydration of aldoximes and amides to nitriles (1) and the amidation of carboxylic acids (4). Only the actual Appel reaction itself, ie., the transformation of alkanols to haloalkanes with BrCCl3-PPh3 is more complex, where under certain conditions the transfer of the bromo-substituent vs. the chloro-substituent is not selective (2). In the following, the authors tried to examine whether amidation reactions of carboxylic acids with the less nucleophilic anilines would proceed equally well as with amines.…”

“…Although there are a number of ways to transform carboxylic acids to acyl halides, the reagents needed such as phosphorus trichloride, phosphorus tribromide, phosphorus pentachloride, phosphoryl chloride, thionyl chloride and sulfuryl chloride are not always available in certain countries. Against this background, the authors developed the reaction system triphenylphosphine (PPh3)bromotrichloromethane (BrCCl3) to prepare acyl halides in situ [1,2]. This reaction system is a variation of the Appel reagent [3], where tetrachloromethane (CCl4) is replaced by the environmentally less hazardous BrCCl3.…”