Tetrahydro-5,5-dimethyl-2 -pyrimidine

Dimethyl-l-(phenyl-acetyl)- E8b, 432 (2,4-Pentandion + Ar — CH2-CO-NH-NH2) Pyrido 4,3-d -l,3-oxazol 6-Methyl-2-phenyl-4,5,6,7-tetrahydro- E8a, Pyrimidine 4-Hydroxy-S-isopropyl-2-phenyl- E9b/2, 100 (R-CH = CH-NR2 + Ar-CO-NCO)... 

Bci 2,4-Dioxo-5-methyl-l - car boxy methyl -1,2,3,4-tetrahydro-pyrimidin (V) konkurriort die Decarboxylierung zu 2,4-Dioxo-l,5-dimethyl-pyrimidin (VI) mit der Photodimerisierung 3 ... 

The relative stereostructure of 9-acetyl-7-hydroxy-l,2-dimethyl-7-meth-oxycarbonyl-4-phenyl-6-oxo-l, 4,7,8-tetrahydro-6/7-pyrido[l, 2-u]pyri-midine-3-carboxylate 122 was justified by an X-ray diffraction analysis (97JOC3109). The stereochemistry and solid state structure of racemic trans-6,9-//-l, 6-dimethyl-9 z-ethoxy-9-hydroxy-4-oxo-l,6,7,8,9,9 z-hexahydro-4//-pyrido[l,2- z]pyrimidine-3-carboxylate (123), adopting a cw-fused conformation, were determined by X-ray investigations (97H(45)2175). 

The A-substituted derivatives of 4-oxo-4//-pyrido[l,2-n]pyrimidine-3-carboxamides and -3-acetamides and l,6-dimethyl-4-oxo-1,6,7,8-tetrahy-dro-4//-pyrido[l,2-n]pyrimidine-3-carboxamide were prepared by treatment of the appropriate 3-carboxylic acids and acetic acid, first with an alkyl chloroformate in the presence ofNEt3 in CHCI3 below — 10°C, then with an amine (98ACH515). A-Phenethyl and A-[2-(3,4-dimethoxyphenyl)ethyl] derivatives of 6-methyl-6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-acetamide were obtained in the reaction of 6-methyl-6,7,8,9-tetrahydro-4//-pyrido[l,2-n]pyrimidine-3-acetic acid and phenethylamines in boiling xylene under a H2O separator. Hydrazides of 4-oxo-4//- and 4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-acetic acid were prepared from the appropriate ester with H2NNH2 H2O in EtOH. Heating 4-oxo-4//- and 6-methyl-4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l, 2-n]pyrimidine-3-acetic hydrazides in EtOH in the presence of excess Raney Ni afforded fhe appropriafe 4-oxo-6,7,8,9-fefrahydro-4//-pyrido[l,2-n]pyrimidine-3-acefa-mide. In the case of the 4-oxo-4// derivative, in addition to N-N bond... 

Cyclocondensation of 2-(nitromethylene)perhydropyrimidine (379) and dimethyl acetylenedicarboxylate yielded a mixture of 9-nitro-l,2,3,4-tetrahydro-6-oxo-6//-pyrido[l,2-n]pyrimidin-8-carboxylate 380 and a pyr-rolo[l,2-n]pyrimidine-7-ylideneacetate 381 (93BCJ2118). Their ratio... 

Dimethyl sulfoxide 1 -Dimethyl-1,4,5,6-tetrahydro-pyrimidine Pyrantel pamoate 3,5-Dinitrobenzoic acid Diatrizoate sodium Dioctyl sodium sulfosuccinate Docusate calcium... 

The carboxyl group of 2-[4-(4-carboxybenzoyl)benzyloxy]-3-methyM77-pyrido[l,2- ]pyrimidin-4-one, prepared by hydrolysis of the methyl ester, was reacted first with (Et02C)20 in DMF at room temperature and then with 4-phenylpiperazine and 4-piperidinopiperidine to give the appropriate amide derivatives <1996EPP733633>. The N-substituted derivatives of 4-oxo-477-pyrido[l,2-tf]pyrimidine-3-carboxamides and -3-acetamides and 1,6-dimethyl-4-oxo-l,6,7,8-tetrahydro-477-pyrido[l,2-tf]pyrimidine-3-carboxamide were prepared by treatment of the appropriate... 

Some interesting fused 1,2,3-triazole ring systems have been reported. A series of 5-piperidyl-substituted 7-hydroxy-3f/-l,2,3-triazolo[4,5-d]pyrimidines 143 has been synthesized from pipecolinate esters, benzylazides, and cyanoacetamide <06CHE246>. 4-Alkylidene-5,6-dihydro-4//-pyrrolo-[l,2-c][l,2,3]triazoles 144 were prepared from alkylidenecyclopropanes via diiodogenation/Cu(I)-catalyzed 1,3-dipolar cycloaddition/intra-molecular Heck reaction sequence <06SL1446>. 6,6-Dimethyl-2-phenyl-4,5,6,7-tetrahydro-27/-benzotriazol-4-one 145 were prepared from A-(5,5-dimethyl-3-oxocyclohexenyl)-S,S-diphenylsulfilimine and... 

In einer Photoreaktion reagiert 2,5-Diphenyl-l,3,4-oxadiazol mit l,3-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-pyrimidin unter Ringspaltung. Das gebildete 5-(a.-Benzoylhydrazono-ben-zyl)-1,3-dimethyl-2.4-dioxo-1.2,3,4-teirahydro-pyrimidm (4 44%) kann zu anderen Folgepro-dukten wciterreagieren78". 

Disubstituierte 5-Brom-6-methyl-2,4-dioxo-l, 2,3,4-tetrahydro-pyrimidine rcagieren mit aliphatischen Aminen in Dimethylformamid unter Ersatz des Brom-Atoms durch eine Amino-Gruppe4. Dagegen erfolgt bei Reaktion mit aromatischen Aminen allylische Substitution durch eine Arylamino-Gruppe, und man erhalt z.B. 6-Anilino-1,3-dimethyl-... 

Dipolar cycloaddition of anhydro pyrido[2,l-b][l,3]thiazinium hydroxides (128) with aryl isocyanates and dimethyl acetylenedicarboxylate gave pyrido[l,2]pyrimidines (129) and quinolizine-l,2-dicarboxylates (130), respectively (76CB3668). 1,4-Dipolar cycloaddition of pyrido[2,l-h][l,3]thi-azinium betaine (131, R = Me) with 1-diethylamino-l-propyne afforded cycloadduct 132, from which quinolizin-4-one 133 formed by a rapid cheletropic extrusion of carbonyl sulfide (93TL5405 95T6651). 1,4-Dipolar cycloaddition of anhydro 4-hydroxyl-2-oxo-6,7,8,9-tetrahydro-2//-pyrido-[2,l-b][l,3]thiazinium hydroxides (131) and 4-phenyl-l,2,4-triazoline-3,5-dione yielded 135 via 134 [94H(39)219 95H(41)1631] and 136 (95T6651). 

Attempts to reduce the quaternary salts of 4-oxo-4//-pyrido[l,2-a]-pyrimidines with sodium borohydride or lithium aluminum hydride remained unsuccessful.137 At the same time the 6,7,8,9-tetrahydro quaternary salts may readily be reduced with sodium borohydride to the 1-alkyl-l,6,7,8,9,9a-hexahydro derivatives.75-77,133 1481269 270 Sodium borohydride reduction of the 1,6- and l,7-dimethyl-3-carbamoyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[l,2-a]pyrimidinium salts proceeds stereoselectively and yields the thermodynamically controlled product.271 The l-methyl-3-carbamoyl-4-oxo-l,6,7,8,9,9a-hexahydropyrido[l,2-a]pyrimidines were also prepared by the catalytic (Pd/C) hydrogenation of the 1,6,7,8-tetrahydro derivatives,270-272 but this reaction led to a diastereoisomeric mixture.271... 

With carbon disulfide and ethanolic potassium hydroxide, ethyl 6-methyl-4-oxo-6,7,8,9-tetrahydro-4ii-pyrido[l,2-tt]pyrimidine gave the dipotassium salt (247), which was methylated with dimethyl sulfate to the 9-methylthio-thiocarbonyl compound (248) and alkylated with 1,2-dibromoethane to the... 

Conformational analysis of 4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l,2-a]pyrimidine-3-acetates and -3-carboxylates 30 (R = H) and their mono-methylated (R = Me, R1 = H) and 6,9-, 7,9-, and 8,9-dimethylated derivatives were carried out by H and l3C NMR spectroscopy (86JOC394). At ambient temperature the 6-methyl derivatives predominantly adopt the energetically most favorable half-chair conformation with a pseudoaxial methyl group. In the other half-chair conformation a serious 1-3 allylic strain exists between the pseudoequatorial methyl group and the adjacent carbonyl group. At the 7- and 8-methyl derivatives the half-chair conformations with equatorial methyl group occur almost exclusively, but the 9-... 

Wamhoff and Huang obtained alkyl 2,3,4,9-tetrahydro-6-oxo-67/-pyrido[l,2-a]pyrimidine-9-carboxylates 237 in the reaction of 3-(hexahy-dropyrimidin-2-ylidene)-2(3.//)-furanones 235 (R3 = H) and methyl propi-olate in a refluxing alcohol in excellent yields (Scheme 17) (84CB1856). When the reactions were carried out in benzene or dioxane, addition products 236 could be isolated, which then were transformed in quantitative yields to tetrahydro-6-oxo-6//-pyrido[ 1,2-a ]pyrimidine-9-carboxyl-ates 237 by stirring in an alcohol at ambient or elevated temperature. When 3-(hexahydropyrimidin-2-ylidene)-2(3//)-furanones 235 (R3 = Me) were reacted with methyl acrylate or with dimethyl acetylenedicarboxy-late, hexahydro- and tetrahydropyridopyrimidin-6-ones 238 and 239, respectively, were obtained in good yields (84CB1926). 

The stability of Chinoin-127 (19) was investigated in the solid state and in aqueous solutions (83MI11 85MI20). By means of TLC the formation of an oxidation product, 1,6-dimethyl-1,6,7,8-tetrahydro-4-oxo-4//-pyrido[l,2-a]pyrimidine-3-carboxamide 355, could be detected. 

Reaction of 3-formyl-4//-pyrido[l,2-a]pyrimidin-4-ones 409 with [(ethoxycarbonyl)methylene]triphenylphosphorane in a Wittig reaction in dimethylformamide at ambient temperature for 10 hours gave 3-trans-acrylates 410 (92JHC559). The 3-formyl group of 3,9-diformyl-l,6,7,8,-tetrahydro and 3-formyl-9-phenylhydrazono-6,7,8,9-tetrahydro-4//-pyr-ido[l,2-a]pyrimidines was transformed to a trans-acrylate side chain in a Wittig reaction with [(ethoxycarbonyl)methylene]triphenylphosphorane in dimethyl sulfoxide at room temperature for 24 hours (84JMC1253). 

The amino moiety of the 3-carbohydrazide group of unsaturated and 6,7,8,9-tetrahydro-4-oxo-47/-pyrido[l,2-n]pyrimidine-3-carbohydrazides was condensed with acetone and 5-nitro-2-furoaldehyde (830MR687 88EUP252809). The reaction of 6-methyl-6,7,8,9-tetrahydro-4-oxo-4//-pyrido[l,2-a]pyrimidine-3-carbohydrazide with diethyl 2-[2-dimethyl-amino)vinyl]-6-methylpyridine-3,5-dicarboxylate in boiling ethanol for 4 hours afforded N-( 1,6-naphthyridin-6-yl)-4-oxo-4//-pyrido[ 1,2-a]pyrimi-dine-3-carboxamide 426 (85MIP1). 

Reaction of aryldiazonium chlorides with sodium 6,9-dimethyl-6,7,8,9-tetrahydro- and 1,6-dimethyl-l, 6,7,8-tetrahydro-4-oxo-4//-pyrido[l, 2-u]pyrimidine-3-carboxylates 582 and 17 in water in the presence of sodium acetate at 5°C gave 9-(aryldiazo) derivatives 583 and 584 (83JMC1126). 

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