Thiazolo pyrimidines, from 5-amino

Ahmed et al. [140] reported the synthesis of thiazolo[5,4-d]pyrimidines from p3uimidines without 5-amino or 5-nitro substituents. The reaction between 5-bromo-4-thioxo-p3mmidi-nones and dimethylcyanamide affords carbodiimide intermediates, which is a very fast... 

Treatment of 2-imino-3-phenyl-4-amino-(5-amido)-4-thiazoline with isocyanates or isothiocyanates yields the expected product (139) resulting from attack of the exocyclic nitrogen on the electrophilic center (276). Since 139 may be acetylated to thiazolo[4,5-d]pyrimidine-7-ones or 7-thiones (140). this reaction provides a route to condensed he erocycles (Scheme 92). 

Thiazolo[5,4-d]pyrimidine, 2,5,7-trichloro-nucleopfulic substitution, 6, 686 Thiazolo[3,2-a]pyrimidine-5,7-diones IR spectra, 6, 672 Thiazolopyrimidines synthesis, 5, 572, 574, 578 Thiazolopyrimidines, amino-purine synthesis from, 5, 591 Thi azolo[3,2-ajpyrimidines synthesis... 

The one-step synthesis of further tri- and tetracyclic pteridine derivatives from 2-aminopyrazine 153 has also been described <2001JHC1173>. Cyclic analogues of A -[bis(methylthio)methylene]amino reagents such as 2-(methylthio)-2-thiazoline, 5,6-dihydro-2-(methylthio)-4//-l,3-thiazine, 2-(methylthio)-2-imidazoline, 2-(methylthio)-l,4,5,6-tetrahydro-pyrimidine, 2-(methylthio)-2-pyrazine, and 2-chloropyrimidine reacted with aminopyrazine 153 to afford thiazolo/thia-zino[2,3-3]- 159 ( = 1 (53%), n = 2 (42%)), imidazo/pyrimidino[2,l-/ ]- 160 ( = 1 (53%), = 2 (57%)), pyrazino[2,l-/ ]-161 (21%), and pyrimido[2,l-/ ]-pteridine 162 (42%) derivatives, respectively. 

Amino-6-mercaptouracil, easily prepared from 6-chloro-5-nitrouracil and sodium hydrosulfide, condenses with formic acid or acetic anhydride to furnish thiazolo[5,4-condensation with chloracetic acid and phenacyl halide gives 6-hydroxy- and 6-arylpyrim-... 

In addition to cyclization of 2-mercaptoadenines with dibromoethane to a mixture of [2,3-Z>] and [3,2-a] isomers (86, 85) shown in Scheme 23, the method starting from 2-aminothiazole also produced this heterocycle. This compound—a cyclic isothiourea—was condensed with ethyl nitrosocyanoacetate to 5-amino-6-nitroso-thia/o 1 o[3,2-nitroso group with sodium dithionite to 6-amino derivative 91 followed by acylation with acyl chloride yielded 5-amino-6-acylaminothiazolo[3,2-u]pyrimidin-7-one (92). Heating 92 with polypho-sphoric acid produced 2-aryl- or 2-heteroaryl-thiazolo[2,3-/)]purin-4(3//)-ones 93. 

The Wittig-type reactions of iminophosphoranes with isocyanates and related compounds have also been extensively used in heterocyclic synthesis. Examples include the preparations of the mesoionic [l,3,4]thiadiazolo[2,3-c][l,2,4]triazines (210) from (209), 0 bicyclic guanidines, e.g. (212), from (211), naphthypyridines (215), (216), and (217) from (213) and (214), 2 pyrido[l,2-f]pyrimido-[4,5-d)pyrimidines (218), 7H-pyrido-[4,3-c]- (219) and 10H-pyrido[3,4-b]- (220) carbazoles, tricyclic fused 2,4-diimino-l,3-diazetidines (222) from the bisiminophosphorane (221), benzotriazepines (225) from (223) and (224), 6 and mesoionic thiazolo-[2,3-b]-1,3,4-thiadiazoles (227) and N,N-bisheteroarylamines from the iminophosphorane (226), derived from 3-amino-4-phenylthiazole-2(3H)-thione. The carbodiimides (229), prepared from the iminophosphorane (228), can be converted into quinolines or a-carboline derivatives depending on the nature of the isocyanate used in the reaction with (228) and the reactions of iminophosphoranes (230) and (231) with aryl and styryl isocyanates provide one-pot syntheses of quinoline, a-carboline, and quinindoline derivatives. 9... 

Cycloaddition and cyclization routes were used to access certain 1,3-diazines. The 4+2 cycloaddition reaction of 4-(N-allyl-N-aryl)amino-l,3-diaza-l,3-butadienes with vinyl-, isopropenyl-, and chloroketene led to pyrimidinone-fused pyrimidinones <97T13841>. Cis-cyclopenta[d]pyrimidines were derived from cis-2-amino-l-cyclopentanecarboxylates by cyclization with KOCN and KSCN <97JHC1211>. 2-Thioxopyrido[3, 2 4,5]thieno[3,2-r/]pyrimidin-4(3//)-ones 19 were prepared by cyclocondensation of 2-carbethoxy-3-amino-4-phenyl-6-substituted-thieno[2,3-/)]pyridines and isothiocyanates <97JHC937>. Thiazolyl-benzimidazoles derived from 2-cyanomethyl-l//-benzimidazole and 2,3-dihydrothiazole-2-(3//)-thiones were cyclized to the corresponding thiazolo[4,5-r/]pyrimidines <97PHA346>. Reductive cyclization of 6-cyanomethyl-5-nitropyrimidines afforded 7-alkyl-5//-pyrrolo[3,2-r/]pyrimidines and 6-amino-7,7-dialkyl-7//-pyrrolo[3,2-rf]pyrimidines <97T391>. 7-Methyl-5-alkyl-2-vinyl-pyrazolo[3,4-r/]pyrimidine-4,6(5//,7//)-diones arose from cyclization and alkylation of... 

On the other hand, thiazolo[5,4-d] pyrimidines also obtained from 5-aminothiazole derivatives, are prepared from aminomalononitrile (or its derivatives) and isothiocyanates [141] or thioesters [142]. The next to 5-amino and 4-cyano (or conforming carboxamide or ester groups) on the thiazole ring are proper functionalities to concept a fused pyrimidine ring system. 7-Aminothiazolo[5,4-d]pyrimidines can be prepared from 5-amino-4-cyanothiazoles by reaction... 

Difluorophenyl)methyl]thio -7- [(1 S,2S)-2-hydroxy-l-(hydroxymethyl)propyl] amino thiazolo [4,5 -d]pyrimidin-2(3H)-one 126 (Seheme 56) which are useful for treating a chemokine mediated diseases sueh as asthma, allergic rhinitis, COPD, inflammatory bowel disease, osteoarthritis, osteoporosis, rheumatoid arthritis, psoriasis, cancer, etc., was prepared in a 7-step process, starting from 4-amino-6-hydroxy-2-mercaptopyrimidine and 2,3-difluorobenzyl bromide [82],... 

The synthesis of thiazolo[4,5-d]pyrimidines has been successfully accomplished by various methods. 4-Amino-5-ethoxycarbonylthiazole derivative has been cyclized to thiazolo[4,5-d]pyrimidine by its reaction with phenyl isothiocyanate [87], Many 4-amino-5-carbamoylthiazole derivatives have been cyclized to the corresponding thiazolo[4,5-d]pyrimidines using triethyl orthoformate/acetic anhydride mixture [88-91], Moreover, 4-amino-5-cyano thiazoles have been used to prepare the same fused ring system via their reaction with triethyl orthoformate, followed by treatment of the intermediate with hydrogen sulfide, guanidine, amines, and isothiocyanates [92, 93], Other thiazolo[4,5-d]pyrimidines have been obtained from 4-amino-5-cyano, carbamoyl, or ethoxycarbonyl thiazoles via cyclization with acetic anhydride [94] or formic acid [95],... 

Thiazolo[3,2-a]pyrimidines [C3NS-C4N2].—Condensation of 6-amino-4-hydroxy-pyrimidine-2-thiol with ethyl a-chloroacetoacetate yields a sulphide, which cyclizes on crystallization from ethanol to give a bicyclic product which is cither compound (82) or its isomer formed by ring-closure at the other nitrogen. Dehydration and acetylation of the amino-group occur with acetic anhydride. 

Pyrrolo[l -a]thiazolo[5,4-e]pyrimidines (C3NS-C4N-C4N2).—A representative of this ring system has been produced from 4-amino-5-ethoxycarbonyl-3-o-tolyl-A -thiazoline by the reaction sequence shown in Scheme 5. ... 

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