Thioesters from acyl halides

The reverse reaction in which thioacetamide is initially alkylated and then reacted under phase-transfer catalytic conditions with the acyl halide results in the formation of A-acylthioamidates (Scheme 4.15), with only trace amounts of the S-alkyl thioesters [35], S-Alkyl thioacetates have also been obtained from trifluoro-methylsulphonyloxy compounds upon reaction with potassium thioacetate in the presence of TDA-1 [61]. It is probable that tetraalkylammonium salts would be equally good catalysts. 

N-Formylsaccharin 102, an easily accessible crystalline compound, has been employed as an efficient CO source in Pd-catalyzed fluorocarbonyl-ation of aryl halides 103 to afford the corresponding acyl fluorides 104 (13OL5370). Reagent KF is expected to serve as a dual role not only as a nucleophile for Pd-catalyzed carbonylation but also as an activator for CO generation from 102. The reactions use a near-stoichiometric amount of the CO source (1.2 eq) and tolerate diverse functional groups. The acyl fluorides 104 can be readily transformed into various carboxylic acid derivatives such as carboxylic acid, esters, thioesters, and amides in a one-pot procedure. 

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