Synthesis and insecticidal bioactivities of 2,3-dihydroimidazo[1,2-a]pyridin-5(1H)-one derivatives

A novel synthesis of 2,3-dihydroimidazo[1,2-a]pyridin-5(1H)-one, and insecticidal derivatives were described.     

Derivatives of phenyl-2,3-dihydroimidazo[1,2-a]pyridinone

The title compounds were prepared by the condensation of a series of β-keto esters with 2-benzylimidazoline. A mechanism is proposed wherein the dienamine 4 undergoes an intramolecular acylation with the elimination of ethoxide and subsequent hydride shift.     

Alkylation studies on 6-ethyl-2,3-dihydrothiazolo-[3,2-A] pyrimidine-5,7-diones

The title compound 7b undergoes alkylation with ethyl iodide or ethyl sulfate at the 7-position yielding the O-ethylated product 10 rather than 6,6-diethyl product 8 as reported previously. Reaction of 7b with mesyl chloride gives 13b which on reaction with potassium carbonate in absolute ethanol also gives 10. Treatment of 7b with phosphorus oxychloride gives 11b which on reaction with potassium carbonate or sodium ethoxide in ethanol produced a mixture from which no 10 was isolated. Authentic 8 was prepared by the reaction of 2-amino-thiazoline with ethyl diethylmalonyl chloride (20) in THF containing triethylamine or by the reaction of 5,5-diethyl-2-thiouracil (18) with excess 1,2-dibromoethane.     

Efficient Synthesis of New Tetracyclic Benzofuro[3,2-d]-imidazo[1,2-a] pyrimidine-2,5-(1 H,3 H)-diones

The aza‐Wittig reaction of iminophosphorane ( 1 ) with aromaic isocyanates gave carbodiimides ( 2 ), which were allowed to react further with (‐amino ester in the presence of a catalytic amount of sodium ethoxide to give selectively new tetracyclic benzofuro[3,2‐d]imidazo[1,2‐a]pyrimidine‐2,5‐(1H,3H)‐diones ( 5 ) in good yields. X‐ray structure analysis of 5i verified the proposed structure and the reaction selectivity.     

A study of some 1-alkyl-2,3-dihydroimidazo[1,2-a]benzimidazoles

A series of 1-alkyl-7-nitro (and 7-amino)-2,3-dihydroimidazo[1,2-α]benzimidazoles has been prepared. Similarly, a series of 1-alkyl-2,3-dihydroimidazo[1,2-α]benzimidazoles has been prepared. The prototropic tautomerism of this system has been studied. The site of electrophilic attack (alkylation) has been examined. 1-Alkylation takes place under strongly basic conditions and 9-alkylation occurs under neutral conditions.     

Synthesis and transformations of 2,3-dioxo-2,3-dihydroimidazo [1,2-a]-benzimidazole derivatives

9-(H)Alkyl-2,3-dioxo-2,3-dihydroimidazo[1,2-a]benzimidazoles were synthesized by the action of oxalyl chloride on 2-amino-1(H)alkylbenzimidazoles and subsequent cyclization of the resulting 2-amino-1-(H)alkyl-3-chlorooxalylbenzimidazolium chlorides in the presence of triethylamine. The behavior of the synthesized benzimidazoles with respect to the action of alkalis, lithium aluminum hydride, and ethylmagnesium bromide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1391–1395, October, 1976.     

Synthesis of 2,3-dihydroimidazo[1,2-a]-pyridines and their salts. (review)

In the present review the published data on the nomenclature, structure, and synthesis of 2,3-dihydroimidazo[1,2-a]pyridines up to 1998 are reviewed. Riga Technical University, Riga, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1321, October, 1999.     

Synthesis of imidazo[1,2-a]pyridine-6-carbohydrazides and 1H-pyrido[1,2-a]pyrimidine-7-carbohydrazides

The one-pot, multicomponent synthesis of imidazopyridine and pyridopyrimidine fused heterocyclic systems from readily available diamines, l,l-bis(methylthio)-2-nitroethene, cyanoacetohydrazide and aromatic aldehydes in good to high yields is described. This protocol has the advantages of simple work-up, mild reaction conditions, absence of catalyst and provides an entry point to fused heterocyclic structures.     

Electron impact ionization mass spectra of some substituted dipyrido[1,2-a:4,3-d]pyrimidinones

The electron impact ionization mass spectra of dipyrido [1,2-a:4,3-d]pyrimidinones are strongly influenced by the degree of aromaticity of the fused rings. The molecular ions of the compounds are fairly stable. The main routes of fragmentation involve formation of the [M – H]⁺ ion and loss of substituents, H₂CN˙, CO and alkyl radicals.     

Pyrimidines. 65. Synthesis of 6-substituted thieno[2,3-d]pyrimidine-2,4(1H,3H)-diones

Several 6-substituted thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives were synthesized. 6-Ethoxycarbonyl derivatives 3 and 7 were prepared by treatment of 6-chloro-5-formyluracil 1 and 6-chloro-5-cyanouracil 6 with ethyl 2-mercaptoacetate in the presence of a base. Electrophilic substitution reactions (Vilsmeier-Haack reaction, bromination, and nitration) of 5,6-unsubstituted thieno[2,3-d]pyrimidine 9 , prepared by condensation of 6-mercaptouracil 8 with chloroacetaldehyde, afforded the corresponding 6-formyl-, 6-bromo-, and 6-nitrothieno[2,3-d]pyrimidines 10, 15 and 16 , respectively.     

Synthesis of 5-Phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

Syntheses are reported for a series of 2-alkylamino-6-phenyl-4-trifluoromethylpyridines. The reaction of 3-cyano-2-(hydroxyalkylamino)-6-phenyl-4-trifluoromethylpyridines with thionyl chloride gave the corresponding 2-(chloroalkylamino)pyridines, 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydro-imidazo[1,2-a]pyridines, and 9-cyano-6-phenyl-8-trifluoromethyl-2,3,4-trihydropyrido[1,2-a]-pyrimidines. X-ray diffraction structural analysis was used to study 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine.     

2,3,5,8(1)-Tetrahydroimidazo[1,2-a]pyrimidine-2,5-dione derivatives

The corresponding ylidene, azomethine, and azo derivatives of 2,3,5,8(1)-tetrahydroimidazo [1,2-a]pyrimidine-2,5-dione were synthesized by reaction of 7-methyl-and 6-bromo-7-methyl-2,3,5,8(1)-tetrahydroimidazo[1,2-a]pyrimidine-2,5-diones with aldehydes, insatin, aromatic nitroso compounds, and arenediazonium salts. Ylidene derivatives of 7-methyl-2,3,5,8(1)-tetrahydroimidazo[1,2-a]pyrimidine-2,5-dione were also obtained by reaction of 2-amino-4-methyl-6-oxo-1,6-dihydro-1-pyrimidylacetic acid with carbonyl compounds.     

Stepwise approach to the 2,3-dihydroimidazo[1,2-a]pyridine and 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine ring systems

The syntheses of 2,3-dihydro-8-fluoro-6-trifluoromethylimidazo[1,2-a]pyridine-3-carbonitrile ( 2 ), 8-fluoro-6-trifluoromethylimidazo[1,2-a]pyridine-3-carbonitrile ( 9 ) and 5-oxo-8-trifluoromethyl-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-3-carbonitrile ( 3 ) are described. These compounds are constructed in a stepwise approach starting from the properly substituted 2-halopyridines.     

Facile and efficient synthesis of 5,7-disubstituted thiazolo[5,4-d] pyrimidine-4,6(5H,7H)-diones

A facile and efficient approach was developed to access 5,7-disubstitued thiazolo[5,4-d]pyrimidine-4,6(5H,7H)-diones through condensation of N-substituted 5-amino-4-carbethoxythiazole with structurally diverse isocyanates in the presence of sodium hydride.The easy availability of substrates and tolerance of structural diversity in this reaction make it attractive to be used for construction of libraries in drug discovery process.     

Derivatives of 2,3-Dihydrocyclopenta[d] pyrido[1,2-a] pyrimidin-10(1H)one

The annulation of 2-amino-3-hydroxy-, 2-amino-3-carboxy-, and 2-amino-3-methylpyridine with ethyl cyelopenlanone-2-earboxylate led to the 5-hydroxy-, 2 , 5-carboxy-, 3, and 5-methyl-, 4 , derivatives of the 2,3-dihydrocycloperita[d]pyrido[1,2-a]pyrimidin-10(1H) one heterocycle. Alkylation of 2 with α-bromotolue, ne gave the 5-benzyloxy derivative.     

Synthesis of novel 2,3-substituted-2,4-dihydro-pyrazolo[4,3-d]pyrimidine-5,7-diones

Novel 2,3-substituted-2,4-dihydro-pyrazolo[4,3-d]pyrimidine-5,7-diones were successfully synthesized with moderate to good yields using a new synthetic approach. The structures of the regio-isomers in this series were determined by single crystal X-ray analysis and NMR spectra.     

Nitration of 2,3-dihydroimidazo[1,2-a]benzimidazole and its N 9-substituted derivatives

7-Nitro-2,3-dihydroimidazo[1,2-a]benzimidazole and its N9-substituted derivatives can be conveniently synthesized by nitration of the corresponding tricyclic precursors with a nitrating mixture or with the HNO3 /CF3COOH system. This reaction occurs fairly smoothly and with good regioselectivity.     

Pyrrolo [1,2-a] [1,3,5] triazine-2,4(1H, 3H)-diones. III—Fragementation under electron-impact

The mass spectra of eight pyrrolo[1,2-a][1,3,5]triazie-2,4(1H, 3H)-diones have been examined. An unusual feature in the fragmentation of those compounds having a 7-alkoxycarbonyl function, namely loss of the whole ester grouping with concomitant hydrogen rearrangement, is discussed.