JXsopropcnyl oxalate, obtained by catalytic addition of oxahc acrd to propyne, is a useful reagent for the access to a variety of adicarhonyl compounds such as oxamides, oxamates and oxalates, under very nuld condrhons. cc-Dicarbonyl compounds are useful synthons in organic chemistry, and the a-dioxo bridge is a key functionality of many elaborated compounds. Esters and amides of general formula ZCOCOZ' (Z, Z'= OR, NR2) have industrial uses as synthetic intermediatesl or co-component in polymerization2. Some of them show biological activity as pesticides3 or pharmaceutics> a-Ketoamides have been prepared by double carbonylation of organic halides with amines in the presence of palladium complexes.5 Oxamides, oxalates and oxamates have been obtained by carbonylation of amines, alcohols or amino alcohols with palladium(H) catalysts.6 These catalytic carbonylation reactions require the use of carbon monoxide and most of them are not selective since monocarbonylation occurs. Some reactive oxamides, oxalates or oxarnatesp such as oxalyldiimidazolet or diacetyloxamide.10 have been used for the synthesis of a-diketo derivatives. Because of the lack of selectivity of the direct carbonylation methods, oxalyl chloride is widely used and allows the access to a variety of a-dicarbonyl compounds, either via Friedel and Crafts reactions with aromatics7 or via acylation of nucleophiles. g The use of oxalyl chloride produces hydrochloric acid and its trapping requires bases which are not tolerated for some pharmaceutical syntheses.
We have previously reported that enol esters were easily available in one step by regioselective addition of carboxylic acids to terminal alkynes, catalyzed by ruthenium@) comp1exes.l r We also have shown that these activated esters were efficient 0-and N-acylation reagents. 12 We now wish to report on the use of diisopropenyl oxalate as a new acylating agent of nucleophiles, which presents the major advantage of releasing acetone as the only by-product on mono-or diacylation reactions under neutral conditions.