S. T. Berman

Acylation of arsenic β-ketoylides by carboxylic acid halides

Conclusions1.In contrast to the corresponding phosphorus ylide, triphenylarsinebenzoylmethylene is acylated by acyl bromides at two reaction centers: at the O and C atoms. Triphenylarsineacetylmethylene gives only an O-acylation product.2.In contrast to the phosphorus analogs, acyloxyvinylarsonium salts rearrange on heating into the C-acylated analogs.3.During rearrangement of β-substituted benzoyloxyvinyltriphenylarsoriium bromides in the presence of sodium acetate and β-substituted acetoxyvinyltriphenylarsonium bromides in the presence of sodium benzoate, one and the same mixture of diacyl ylides is formed. It was shown that the rearrangement proceeds via the stage of splitting of the acyl group, followed by C-acylation of the ylide formed by an anhydride.

Acylation of arsenic β-ketoylides by trifluoroacetic anhydride

Conclusions1.Ambident arsenicβ-ketoylides are acylated by trifluoroacetic anhydride at the O atom of the carbonyl group to give diacyltriphenylarsinomethylenes.2.In contrast to their phosphorus analogs, the diacyltriphenylarsinomethylenes are cleaved by strong acids with rupture of either the CF3CO-C bond or the As-C bond.

Acylation of phosphorusβ-ketoylides by acid chlorides

ConclusionsContrary to the previously described results, the reaction of theβ-oxoalkylidenetriphenylphosphoranes with the acid chlorides of the p-nitrobenzoic, cinnamic, and phenylacetic acids gives only the acyloxyvinylphosphonium salts. As a result, all of the currently known reactions of phosphorusβ-ketoylides with acid chlorides lead to the O-acylation products.

Reaction of phosphorus ylids with perfluorobenzene

1. Triphenylphosphinemethylenes react with perfluorobenzene to form triphenylphosphinepentafluorophenylmethylenes. 2. Pentafluorostilbenes were obtained from triphenylphosphinepentafluorobenzylidene via the Wittig reaction.