R. I. Vas’kevich

Electrophilic heterocyclization of 6-alken(yn)ylsulfanyl-pyrazolo[3,4-d]pyrimidin-4(5H)-ones

Abstract6-Allylsulfanyl-1-arylpyrazolo[3,4-d]pyrimidin-4(5H)-ones react with iodine and sulfuric acid to give angular pyrazolothiazolopyrimidine derivatives. The reaction of 6-(prop-2-yn-1-ylsulfanyl)-1-(4-tolyl)-pyrazolo[3,4-d]pyrimidin-4(5H)-one with sulfuric acid gives angularly fused pyrazolo[4,3-e][1,3]thiazolo-[3,2-a]pyrimidin-4-one, whereas in the reaction with sodium methoxide linearly fused pyrazolo[3,4-d][1,3]-thiazolo[3,2-a]pyrimidin-4-one was formed. Linearly fused pyrazolo[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazole derivatives were also obtained by reaction of 1-aryl-6-(3-phenylprop-2-en-1-ylsulfanyl)pyrazolo[3,4-d]pyrimidin-4(5H)-ones with sulfuric acid.

Synthesis of amino derivatives of triazolopyrimidine

Heterocyclization of 1-(4,6-dimethylpyrimidin-2-yl)-4-R-thiosemicarbazides by the action of methyl iodide in ethanol in the presence of sodium acetate is accompanied by Dimroth rearrangement leading to the formation of 5,7-dimethyl-2-R-amino[1,2,4]triazolo[1,5-a]pyrimidines. Analogous heterocyclization of 4-aryl-1-(4-methyl-6-oxo-1,6-dihydropyrimidin-2-yl)thiosemicarbazides gives 3-arylamino-7-methyl-5-oxo-[1,2,4]triazolo[4,3-a]pyrimidines. The presence in the pyrimidine ring of a carbonyl group capable of forming hydrogen bond with protons of the amino group stabilizes the molecule, thus hampering the Dimroth rearrangement.

Fused pyrimidine systems: XIII. Synthesis and some transformations of 1,3-thiazolo(thiazino)-fused pyrido[3,4-d]pyrimidines

Abstract2-[Allyl(propargyl)sulfanyl]pyrido[3,4-d]pyrimidin-4-ones at heating in polyphosphoric acid undergo an intramolecular cyclization with the formation of pyrido[4,3-e]thiazolo-[3,2-a]pyrimidin-5-ones of angular structure. Under similar conditions the cyclization of 2-(cinnamylsulfanyl)pyrido[3,4-d]-pyrimidin-4-one results in a linear pyrido[3′,4′:4,5]pyrimido-[2,1-b][1,3]thiazin-6-one. The iodocyclization of the same substrates affords the corresponding 9-(iodomethyl)(iodomethylidene)pyrido[4,3-e][1,3]thiazolo-[3,2-a]pyrimidin-5-ones and 3-iodopyrido[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazin-6-one of angular structure. 9-(Iodomethyl)-8,9-dihydro-5H-pyrido[4,3-e][1,3]thiazolo[3,2-a]pyrimidin-5-one treated with sodium azide gave 9-(azidomethyl) derivative whose cyclization with substituted alkynes in the presence of copper compounds provided pyrido [4,3-e][1,3]thiazolo[3,2-a]pyrimidinylmethyltriazoles.

Synthesis of fused triazolothienopyrimidine derivatives

Reactions of substituted 1-(thieno[2,3-d]pyrimidin-2-yl)-4-arylthiosemicarbazides with methyl iodide led to the formation of fused triazolothienopyrimidine derivatives.

Fused pyrimidine systems: XVI. Electrophilic intramolecular cyclization of 2-(alkenylsulfanyl)pteridin-4(3H)-ones

Abstract2-[Allyl(but-3-en-1-yl, pent-4-en-1-yl)sulfanyl]pteridin-4(3Н)-ones at heating in polyphosphoric acid undergo an intramolecular cyclization affording respectively 9-methyl-8,9-dihydro-5H-[1,3]thiazolo[3,2-a] pteridin-5-one and 10-methyl(ethyl)-9,10-dihydro-5Н,8Н-[1,3]thiazino[3,2-a]pteridin-5-ones of angular structure. The cyclization of 2-(alkenylsulfanyl)pteridin-4(3Н)-ones under the action of iodine or arylsulfenyl chlorides afforded iodo(arylsulfanyl) derivatives of angularly fuzed thiazolo- and thiazinopteridines.

Electrophilic intramolecular cyclization of functional derivatives of unsaturated compounds: V. Cyclization of anilides of styrylacetic acids in polyphosphoric acid

Anilides of styrylacetic acids at heating in polyphosphoric acid undergo an intramolecular cyclization giving 1,5-diarylpyrrolidin-2-ones, 5-aryl-1,3,4,5-tetrahydro-2H-benzazepin-2-ones, and 5-(3-fluorophenyl) dihydrofuran-2(3H)-one, where the ratio of the products depends on the character of the aromatic substituents in the amide and styrene fragments of the substrate.

Synthesis of New Imidazo(1,2-a)pyrazolo(4,3-e)pyrimidin- 4(6H)-one Derivatives by Iodocyclization of 6-Alkenyl(alkynyl)- aminopyrazolo(3,4-d)pyrimidin-4(5H)-ones

Abstract6-Allyl(diallyl, prop-2-yn-1-yl)amino-1-R-pyrazolo[3,4-d]pyrimidin-4(5H)-ones reacted with iodine to give angularly fused 8-iodomethyl-7,8-dihydro-1-R-imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(6H)-ones which were treated with sodium acetate to obtain 8-methylidene-1-R-7,8-dihydroimidazo[1,2-a]pyrazolo-[4,3-e]pyrimidin-4(6H)-ones as a result of elimination of hydrogen iodide. 8-Methylidene-1-R-7,8-dihydroimidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(6H)-ones were converted into 8-methyl-1-R-imidazo[1,2-a]pyrazolo-[4,3-e]pyrimidin-4(5H)-ones on heating to the melting point. 8-Methylidene-1-phenyl-7,8-dihydroimidazo-[1,2-a]pyrazolo[4,3-e]pyrimidin-4(6H)-one underwent isomerization into linearly fused 6-methyl-1-phenyl-1,8-dihydro-4H-imidazo[1,2-a]pyrazolo[3,4-d]pyrimidin-4-one on heating in sulfuric acid.

Fused pyrimidine systems: XIV. Reaction of 2-alkenyl(alkynyl)sulfanylpyrido[3,4-d]pyrimidin-4(3H)-ones with arylsulfanyl chlorides

Abstract2-Allylsulfanylpyrido[3,4-d]pyrimidin-4(3H)-one reacted with arylsulfanyl chlorides in chloroform to give addition products to the exocyclic double bond, which were converted into linearly fused arylsulfanylthiazinopyridopyrimidines by the action of sodium acetate. The reactions of 2-allyl(cinnamyl, propargyl)sulfanylpyrido[3,4-d]pyrimidin-4(3H)-ones with arylsulfanyl chlorides in the presence of an equimolar amount of lithium perchlorate afforded angularly fused arylsulfanylmethylthiazolo- and -thiazinopyridopyrimidines.

Fused pyrimidine systems: XV. Intramolecular electrophilic cyclization of 2-allyl(propargyl, cinnamyl)amino-pyrido[2,3-d]pyrimidin-4(3H)-ones

Abstract2-(Allylamino)- and 2-(propargylamino)pyrido[2,3-d]pyrimidin-4(3H)-ones underwent intramolecular cyclization on heating in polyphosphoric acid to give angularly fused imidazo[1,2-a]pyrido[3,2-e]pyrimidin-5-ones. The cyclization of 2-(cinnamylamino)pyrido[2,3-d]pyrimidin-4(3H)-one under analogous conditions afforded linearly fused 4-phenyl-1,2,3,4-tetrahydro-6H-pyrido[2,3-d]pyrimido[1,2-a]pyrimidin-6-one. 2-(Allylamino)pyrido[2,3-d]pyrimidin-4(3H)-one reacted with iodine yielding 9-(iodomethyl)-8,9-dihydroimidazo[1,2-a]pyrido[3,2-e]pyrimidin-5(7H)-one as the major product, 2-(propargylamino)pyrido[2,3-d]pyrimidin-4(3H)-one gave rise to iodine addition product to the triple bond, and angularly fused 9-iodo-10-phenyl-7,8,9,10-tetrahydro-5H-pyrido[3,2-e]pyrimido[1,2-a]pyrimidin-5-one was obtained from the 2-(cinnamylamino) derivative. Electrophilic cyclization of 2-(allylamino)- and 2-(cinnamylamino)pyrido[2,3-d]pyrimidin-4(3H)-ones by the action of phenylsulfanyl chloride led to the formation of angularly fused 9-(phenylsulfanylmethyl)-8,9-dihydroimidazo[1,2-a]pyrido[3,2-e]pyrimidin-5(7H)-one and 10-phenyl-9-phenylsulfanyl-7,8,9,10-tetrahydro-5H-pyrido[3,2-e]pyrimido[1,2-a]pyrimidin-5-one.

Heterocyclizations of 1-(Benzothiazol-2-yl)-4-phenylthiosemicarbazide

Abstract1-(Benzothiazol-2-yl)-4-phenylthiosemicarbazide reacted with methyl iodide in the presence of sodium acetate in boiling ethanol to give 2,2′-dithiobis[N-(5-methylsulfanyl-4-phenyl-4H-1,2,4-triazol-3-yl)-benzenamine]. The reaction of the title compound with dimethyl acetylenedicarboxylate in dioxane led to the formation of methyl 3-(benzothiazol-2-yl)-2-(2-methoxy-2-oxoethyl)-2,3-dihydro-1,3,4-thiadiazole-2-carboxylate.