5 -Chloro-1,2,4-triazolo pyrimidine

Reaction of 5-chloro-l,2,4-triazolo[l,5-c]pyrimidines (165) with sodium hydroxide, thiourea, or hydrazine hydrate (79AJC1585) or with sodium azide (85EUP152841) also caused the displacement of the chlorine atom to... 

Heating the 8-amino-7-chloro-2-oxo-l,2,4-triazolo[l,5-c]pyrimidine 189 with hydrochloric acid caused hydrolysis of the chloro group yielding the 2,7-dioxo derivative 190 (68JOC530) (Scheme 72). 

Schiff bases (112) derived from 4-chlorobenzaldehyde and 1-substituted-5-amino-3-methylthio-l,2,4-triazoles (111) underwent cyclization with phe-noxyacetyl chloride or dichloroacetic acid in the presence of phosphoryl chloride and dimethylformamide to give the 7-(4-chlorophenyl)-fram-6,7-dihydro-3-methylthio-6-phenoxy-l-substituted-l,2,4-triazolo[4,3-a]pyrimidin-5-one 113 and l-substituted-6-chloro-7-(4-chlorophenyl)-3-methylthio 1,2,4-triazolo[4,3-a]pyrimidin-5-one 114, respectively (88JHC173) (Scheme 47). 

Reaction of the chloro derivative 210 with thiourea gave the thiolo derivative 211 [88IJC(B)825]. Displacement of the chlorine in 212 with 2-chlorothiophenol formed 2-(arylthio)-l,2,4-triazolo[l,5-a]pyrimidine (213) (89EUP337232) (Scheme 39). 

Reaction of 4-chloro-5-methyl-6-phenyl-2-pyrimidinamine (566) with formylhydrazine yielded a mixture of triazolo[4,3 c]pyrimidine (567) and its [l,5-c]isomer 568 (83USP4405780), and boiling 566 with formylhydrazine in DMF containing a 3-A molecular sieve afforded 567 (81GEP3029871) (Scheme 110). 

Methyl-5-oxo-l,5-dihydro-8-carbamoyl-l,2,4-triazolo[4,3-c]pyrimidines 577 and 578 were prepared by the cyclization of 576 with acetic anhydride and ethyl oxalate, respectively (89PHA604).The 4-methyl-l,2-dihydropyra-zolo[3,4-d]pyrimidine-3,6-dione 579 also was obtained in the latter case, as a consequence of breaking the amide bond and releasing the amine moiety. Coupling ethyl dithioacetate and 5-chloro-4-hydrazinopyrimidine (580) afforded the triazolo[4,3-c]pyrimidine 581 (89H239) (Scheme 114). 

Chloro-3-formyl-4-oxo-4/Y-pyrido[l,2-a]pyrimidine was transformed with hydrazine and ethylenediamine, respectively, to the tricyclic compounds 22898 and 229.285 Treatment of 2,3-diamino-4-oxo-4//-pyrido[l,2-a]pyrim-idines with sodium nitrite in aqueous acetic acid afforded the pyrido [1,2-a]-r-triazolo[4,5-d]pyrimidines (230).31 Reaction of the pyrido[l,2-a]pyrimi-... 

The halogen metal exchange reaction between 7-bromo or 7-iodo-3-phenyltriazolopyrimidine 165 and butyllithium in iV,N,N, N -tetra-methylethylenediamine afforded the 7-lithio compound 166, whereas a similar reaction with the 7-chloro derivative 165 (R = H) gave the ring-fission product, 5-amino-l-phenyl-l//-l,2,3-triazole-4-carbonitrile 169 (91 CPB2793). Reaction of 166 with electrophiles such as benzaldehyde and ketones gave 170 and 167 respectively, together with 7,7 -bis[3-phenyl-3//-1,2,3-triazolo[4,5-d]pyrimidine] 168 (Scheme 34). 

The carbocyclic nucleoside analogs 342-344 were prepared by diazo coupling of (lJ mJ-S-pyrimidylaminomethyl-l -trimethylcyclopentyl-methanol (339) with 4-chlorobenzenediazonium chloride to give 340, which upon reduction gave the triamine 341. Ring closure of 341 with nitrous acid gave (17 ,c/s)-3-[(5-amino-7-chloro-3//-l,2,3-triazolo[4,5-d]pyrimidin-3-yl)-... 

Pyrazolo[4,3-d]pyrimidine and pyrazolo[3,4-d]pyrimidine sulfonamides have been synthesized as selective calcitonin inducers <02JMC2342>. A series of para-substituted 3-arylpyrazolo[3,4-d]pyrimidines have been synthesized and evaluated as inhibitors of lck kinase <02BMCL1687). The synthesis of 3-aryl-pyrazolo[4,3- f]pyrimidines as potential corticotropin-releasing factor (CRF-1) antagonists has been described <02BMCL2133>. Cyclization of 4-chloro-5-heteroimine-l,2,3-thiadiazoles furnished pyrazolo[3,4-d]pyrimidines, triazolo[4,5-d]pyrimidines and purines <02BMC449>. 

Dealkylation, of azolium quaternary salts and betaines, 60, 244 Deazaflavines, bent, 55, 192 5-Deazalumazines, see Pyrido[2,3-(/]pyrimidine-2,4-diones Deaza-purines, -flavines, etc., see the systematically-named ring systems 4-Deazatoxoflavins, syntheses, 55, 182 Dechlorination, catalytic, of chloro-[ 1,2.4]triazolo[ 1,5-a]pyrimidines, 57, 125... 

Studies of allyl ether migrations in this system have stemmed solely from the efforts of Makisumi.23,24 By reacting 5-methyl-7-chloro-s-triazolo-(l,5-a)pyrimidine with sodium allyloxide in allyl alcohol at room temperature, the corresponding 7-allyloxy derivative was obtained. When this was rearranged at 150°, during 30 minutes, seven different products were obtained. These were separated into chloroform-soluble and chloroform-insoluble material. Out of the latter, by fractional crystallization two products were isolated. One of these was... 

Alkaline conditions favor the formation of triazolo[4,3-c]pyrimidines (91). Thus, on heating in an aqueous solution of NaHCOj, 4-chloro-5-amino-6-(ethoxycarbonyl)hydrazinopyrimidine (95) is converted to triazole 96. The action of diethoxymethylacetate on 95, followed by heating in hydrochloric acid, gives 9-aminopurine 97 (63JOC2257). 

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