Thioacyl anhydrides thioacylation

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... 

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

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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