Thioacyl anhydrides

Thioacylation of Thiols with Thioacyl Halides, Thioacyl Anhydrides and Thioketenes... 

The most suitable synthetic method for these products is the heterocyc-lization reaction of N-thioacyl derivatives of amino acids (202) with phosphorus tribromide (378, 442-450, 559, 560) or anhydrous trifluoroacetic acid (448, 449, 451, 452) (Scheme 103). Treatment of N-thioacyl amino acids with acetic anhydride leads directly to the thiazolylacetate without isolation of an intermediate thiazolinone (365. 452). 2-Alkoxy-derivatives of A-2-thiazoline-5-one, however, can be obtained without acetylation by this method (453, 454). 

Substituted 5-hydroxythiazoles (267b), Rj = alkylmercapto, acyl-amino, and sec-amino, are prepared by cydization of N-thioacyl-amino acids (266) with phosphorus tribromide or acetic anhydride (Scheme 137) (317, 350). i en the cydization of 266, R2 = H, is carried out with acetic anhydride in the presence of benzaldehyde (317, 325) or ethylformate (317), the benzylidene (268), R2=Ph, Rj = SR or CH2Ph, or 4-ethoxymethylene (268), Rj = SR and R2 = OEt, derivative is obtained directly (Scheme 138). 

Thioacylation of Alcohols and Phenols with Anhydrides, Thiokeienes, Thioesters and Dithioesters... 

The utility of various thioxo- and dithio-carboxylic anhydrides was recently reviewed by Martin and Bamikow, who pointed out that bisthioacylthioanhydrides and the mixed anhydrides of thiocarbox-ylic and diphenyldithiophosphinic acids are effective thioacylating agents for alcohols (equation 46), whereas carboxylic dithiocarboxylic anhydrides transfer an acyl group to a nucleophile. 

Phenyl carbodithioates are obtained in acceptable yields by an intramolecular thioacylation according to equation (59).The intermediate mixed thiocarboxylic thiocarbonic acid anhydride is not isolated but spontaneously eliminates carbon oxysulfide. 

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