Pyridine-2-thione, reaction with acetate

The reaction of 6-amino[l,2,4]triazin-5(2//)-ones or its thione derivatives 680 with acetic anhydride gave the 6-acetamido derivatives 681 and 682, respectively. Treatment with phosphorus pentasulfide in pyridine gave thiazolo[5,4-e][l,2,4]triazines 683 (84LA283 87AJC491) (Scheme 142). 

Methyl-4-oxoquinazolinyl-2-thiolacetic acid (378), obtained by the reaction of 6-methyl-4-oxoquinazoline-2-thione (377) and chloroacetic acid, upon treatment with acetic anhydride-pyridine, yields a cyclized product confirmed by the molecular ion peak [M] at m/z 232 and for which structure 7-methyl-2//-thiazolo[3,2-n]quinazolin-l,5-dione (379) was assigned on the basis of IR and H-NMR data in preference to possible... 

Reaction of 3//-imidazo[4,5-y]quinoline-2-thione (404) with chloroacetic acid gives acid 405 which, on treatment with a mixture of acetic anhydride and pyridine, undergoes cyclization to furnish a product confirmed by the appearance of a band at 1735 cm (N—C=0) and molecular ion peak [M] at m/z 241. Thiazolo[2, 3 2,3]imidazo[4,5-y]quinolin-6(7//)-one (406), in preference to the other possible isomer thiazolo[3, 2 l,2]-imidazo[4,5-y]quinolin-8(7//)-one (409), was assigned to the cyclized product on the basis of the comparative studies of proton signals of the cyclized product (406 or 409) with those of 407 or 408 (obtained by the reaction of 404 and 1,2-dibromoethane), as well as with the proton signals of acid 405 [86IJC(B)264] (Scheme 93). 

The 3-imino group of 4-cyano-2-ethyl-3-imino-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidine-l-thione was acylated with phenyl isocyanate (78MI1). The imino group of l-imino-4-cyano-3-methylthio-l//-pyrido[l,2-cjpyrimidine was alkylated and acylated with methyl iodide and acetic anhydride (75YZ13). Reaction of 3-amino-4-phenyl-4-[2-(A, N-di-n-pro-pylamino)ethyl-4,4 a,5,6,7,8-hexahydro-l //-pyrido[l, 2-c ]pyri midin-l-one with acetic anhydride in pyridine and with sodium nitrite in aqueous acetic acid afforded 3-acetamido and perhydro-l,3-dioxo derivatives, respectively (87USP4680295). 

Thiazolo-[4,5-d]- and -[5,4-d]-pyrimidines [C3NS-C4N2]. The reaction of the A" -thiazoline (139) with NaSH or with H2S and pyridine gives the thiazolo-[4,5-i/]pyrimidine-7-thione (140 R = Ac, R = H, X = S), and with acetic anhydride and PPA yields (140 R = H, R = Me,X = O), whilst the readily available ethyl 2-methylmercapto-5-aminothiazole-4-carboxylate will react with formamide to give the thiazolo[5,4- f]pyrimidin-4-one (141). ... 

Chiral imidazoUdin-2-thione or 2-one were prepared from o-glucoseamine by reaction with o,o -disubstituted arylisothiocyanates to give 39 which can be cycHzed to 40 [76]. Thus, a variety of derivatives were prepared carrying different aryl groups and as a consequence of hindered rotation, some of them exist as stable rotamers (Fig. 7). Treatment of 39 with acetic anhydride in pyridine at low temperature gave the respective per-O-acetyl derivative imidazolidine thione, which upon elimination of acetic acid gave the imidazoline thion 41 as a mixture of atropisomers [76]. 

Cyclization occurs directly through catalysis by the acid liberated when a pyridine-2(lH)-thione is heated with an a-halo acid ester. The most convenient method for preparing the thiazole, however, seems to be the cyclization of (2-pyridinethio)acetic acids in acetic anhydride in the presence of pyridine. Without base catalysis the reaction is slow, which suggests a mixed anhydride intermediate. Mixed anhydride formation with ethyl chlorofor-mate in pyridine, or carboxyl activation by DCC in pyridine, gives the mesoionic product. The cyclization reaction and the chemical stability of the thiazole are adversely affected by a pyridine 6-substituent. The initially formed acylpyridinium salt (407) undergoes rapid tautomerization to the aromatic thiazole form equilibrium between the forms (407) and (408) is verified by rapid deuteration at C-2 (R1 = H) in AcOH-d (81H(15)1349). 

In the presence of acetic acid and pyridine, 5-phenyl- or 5- eri-butyl-3-methylthio-l,2-dithiolium ions have been reacted with cyanoacetone to give, in the usual way, an a-(l,2-dithiol-3-ylidene) ketone. A similar reaction has been observed with 4-hydroxy-6-methylpyran-2-one and with 4-hydroxy-coumarin (Eq. 23). In the same way, 4-hydroxy-6-methylchromene-2-thione and 3-methylthio-5-phenyl-l,2-dithiolium cation gave the fused trithiapentalene 59. ... 

In the Taylor synthesis of (III.28) [31], aldehyde (HI.32) was obtained by reaction of2-amino-3-cyano-5-(dimethoxymethyl)pyridine and guanidine, followed by cleavage of the acetal with aqueous formic acid. The pyridine aminonitrile was elaborated in a sequence of high-yield steps from 3-cyano-5-methylpyridine-2-thione. These steps consisted of the following (yields in... 

Nayak observed" that l-(2-pyridyl)thiourea reacted with chloroacetic acid in ethanolic solution in the presence of sodium acetate to yield 2-(2-pyridyl-imino)thiazolidin-4>one, whereas the same reaction afforded 3-(2-pyridyl)-thiohydantoin when performed in pyridine solution. On treatment with chloroacetic acid in pyridine, p-bis(thioureido)biphenyl (323) similarly yielded p-bisCthiohydantoin-S-yObiphenyl." The reactions of monosubsti-tuted thioureas with -unsaturated /3 -dichlorocarbonyl compounds and 2-(l-chlorocyclohexyl)cyclohexanone afforded 1,3-thiazine- thiones and the spiro-compounds (324), respectively. 

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