A NEW ROUTE TO N-MONOSUBSTITUTED THIOAMIDES UTILIZING PHOSPHORAMIDOTHIONATES AS REAGENTS FOR THE THIOAMIDATION OF CARBOXYLIC-ACIDS

Several N-monosubstituted thioamides have been synthesized from the corresponding carboxylic acid chlorides and primary amines by a new procedure. The procedure utilizes a commercially available and inexpensive organophosphorus reagent (dimethyl chlorothiophosphate) to derivatize the amine, form the carboxamide bond, and accomplish the thionation of the carbonyl by an intramolecular rearrangement. The phosphoryl group is then cleaved from the resulting thiocarbonyl phosphoryl mixed imide by a simple hydrolysis. Thioamides (RCSNHR') containing a variety of functionality (R = simple alkyl, phenyl, bulky alkyl, cycloalkylalkyl, α,β-unsaturated, and alkyl with remote keto, ester, or amide carbonyl groups; R’ = methyl, benzyl, allyl) have been prepared by this method in generally high overall yields (50-80%). Competing thionation of remote carbonyl groups or epimerization of a chiral center containing a proton a to a ketone group was not observed. © 1990, American Chemical Society. All rights reserved.