Cycloaddition of 2-acylmethyl-1H-benzimidazoles to 4-arylidene-1,3-oxazol-5-ones

Cycloaddition of 2-phenacyl-1H-benzimidazole to 2-phenyl-or 2-methyl-4-arylidene-1,3-oxazol-5-ones occurs regioselectively to form the previously unknown N-(3-aryl-4-benzoyl-1-oxo-1,2,3,4-tetrahydropyrido[1,2-a]benzimidazol-2-yl)benz-and-acetamides. The analogous cycloaddition of the 2-acetonyl-1H-benzimidazole is complicated by prototropic isomerization and leads to the corresponding 1,2,3,5-tetrahydropyrido[1,2-a]benzimidazole. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 78, pp. 1008–1014, July, 2007.     

Chemistry of Indolopyridines with a Bridgehead Heteroatom. (Review)

Published data on the synthesis and reactions of indolopyridines with one bridgehead heteroatom and their benzannelated derivatives are reviewed for the first time.     

吡啶叶立德与查尔酮1,3-偶极环加成反应制备2-苯基-3-乙酰基中氮茚

报道在氧化剂存在下吡啶叶立德与查尔酮进行1,3-偶极环加成反应, 一锅法合成2-苯基-3-乙酰基中氮茚化合物的方法, 收率37%. 用类似的方法由α-溴代异喹啉季铵盐、查尔酮、碱和氧化剂进行反应, 可一锅法得到1-苯甲酰基-2-苯基-3-乙酰基吡咯并[2,1-a]异喹啉, 收率58%.     

Spatial Configuration of Derivatives of 5,5a,6,7-Tetrahydropyrido[1,2-a]benzimidazole and 6,7-Dihydro-5aH-pyrido[1,2-b]benzoxazole

The spatial configurations of 7,9-diphenyl-5a,6-tetramethylene-5,5a,6,7-tetrahydropyrido[1,2-a]benzimidazole and 7,9-diphenyl-5a,6-tetramethylene-2,5a,6,7-tetrahydropyrido[1,2-a]benzimidazol-2-one have been established by X-ray crystallography. Analogous configurations are proposed for a series of other derivatives of 5,5a,6,7-tetrahydropyrido[1,2-a]benzimidazoles and some derivatives of 6,7-dihydro-5aH-pyrido[1,2-b]benzoxazoles on the basis of ¹H NMR spectroscopic data and the results of quantum chemical calculations using the MNDO, AM1, and PM3 methods.     

11H-isoindolo[2,1-<Emphasis Type="Italic">a</Emphasis>]benzimidazoles (Review)

Data on methods for the synthesis of isoindolo[2,1-a]benzimidazole and its derivatives and their chemical characteristics are reviewed. Data from quantum-chemical calculations of certain structures are presented. Possible practical applications of the compounds are indicated. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 323–351, March, 2007.     

Indolopyridines containing a bridgehead heteroatom. 12. Synthesis and reduction of 12-arylidene-5,6-dihydroindolo[2,1-a]isoquinolinium trifluoroacetates

Condensation of 5,6-dihydroindolo[2,1-a]isoquinoline with aromatic aldehydes in trifluoroacetic acid afforded 12-arylidene-5,6-dihydroindolo[2,1-a]isoquinolinium trifluoroacetates. Hydrogenolysis of these salts on rhenium heptasulfide at elevated temperature and hydrogen pressure yielded indolo[2,1-a]isoquinolines, while reduction with sodium borohydride gave 12-arylmethylindoloisoquinolines. Photoluminescence was found for some indolo[2,1-a]isoquinolines.     

Recyclization of Condensed Carbethoxypyrimidines Accompanied by Substitution of a Carbon Atom into the Heterocycle

Condensation in ethanol of ethyl ethoxymethyleneacetoacetate with systems containing an amidine fragment (substituted 3-aminopyrazoles and 3-amino-1,2,4-triazole) gave 6-carbethoxy-7-methylpyrazolo[1,5-a]pyrimidines. Addition of base to solutions of the obtained bicyclic carbethoxy derivatives in the course of several minutes caused rearrangement to 6-acetyl-7-hydroxypyrazolo[1,5-a]pyrimidine and 6-acetyl-7-hydroxy-1,2,4-triazolo[1,5-a]pyrimidine respectively. A more prolonged refluxing in 15% aqueous alcohol solution of base caused 6-carbethoxy-7-methyl-2-phenylpyrazolo[1,5-a]pyrimidine and 6-acetyl-7-hydroxy-2-phenylpyrazolo[1,5-a]pyrimidine to recyclize to 7-methylpyrazolo[1,5-a]pyrimidine.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 569–576, April, 2005.     

Cycloaddition in Condensed Isoindoles. 3. Synthesis of Novel Tricyclic Derivatives of the 7-Azabenzonorbornene System

We have studied the reaction of 6-methyl-5,6-dihydroisoindolo[2,1-a]quinazolin-5-one with maleinimide derivatives for a 1:2 reagent ratio. We have shown that the reaction products are tricyclic derivatives of the 7-azabenzonorbornene system, and specifically 11-(2,5-dioxo-1-R-tetrahydro-1H-3-pyrrolyl)-2-methyl-20-R-2,10,20-triazahexacyclo[9.6.5.0^1,10.0^4,9.0^12,17.0^18,22]docosa-4(9),5,7,12(17),-13,15-hexaene-3,19,21-triones. We discuss a hypothesis for a probable reaction mechanism.     

Nitriles in Organic Synthesis: Synthesis of Pyrido[2,1-b]benzothiazole Derivatives and Polyfunctionally-substituted Pyridines

A variety of pyrido[2,1-b]benzothiazole derivatives could be prepared by reaction of 2-cyanomethylbenzothiazole, formaldehyde, and various active methylene reagents. Also some polyfunctionally-substituted pyridines were prepared by reaction of 2-cyanomethylbenzothiazole, formaldehyde, and an -functionally substituted acrylonitrile.     

3-Acetyl-4-methylpyrido[2,1-a]-isoquinolin-2-ones. [2+4] cyclocondensation of 3,4-dihydroisoquinolines with triacetylmethane

Treatment of 3,4-dihydroisoquinolines with triacetylmethane in refluxing alcohol for 2-3 h gave 3-acetyl-4-methylpyrido[2,1-a]isoquinolin-2-ones. Their basic physicochemical properties have been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 77–85, January, 2006.     

Pd-mediated synthesis of novel pentacyclic benzoazepino[2,1-a]isoindoles from enamides of Baylis-Hillman adducts

Novel pentacyclic benzoazepino[2,1-a]isoindole derivatives were synthesized by palladium-mediated consecutive cyclization from enamides of Baylis-Hillman adducts.     

Reaction of 1,3-Dibromo- and 1,3-Dichloroacetone with 2-Aminoazaheterocycles

The reactions of 1,3-dibromoacetone with 2-aminoazines and 2-aminoazoles has been carried out for the first time and the pure intermediate quaternary salts have been isolated. They undergo cyclization to the corresponding imidazoazines and imidazoazoles containing a bromomethyl group. Similar condensations were carried out with 1,3-dichloroacetone.     

Synthesis of New Imidazo[4,5-b]pyridine Derivatives

New imidazo[4,5-b]pyridine derivatives with various substituents in the 2-position (,-unsaturated ketones, imines, ²-pyrazolines, pyrimidines, 1,2,3,4-tetrahydropyrimidines) and derivatives of the new pyrido[3',2':4,5]imidazo[1,2-d][1,2,4]triazine ring system were synthesized. Biological data for selected compounds are presented.     

Condensed Pyridopyrimidines. 7. Synthesis of Condensed Triazolo[4,3-c]- and Tetrazolo[1,5-c]pyrimidines

Novel dihydro-5H-pyrano[3',4':5',6']pyrido[2,3-d]-1,2,4-triazolo[4,3-c]pyrimidines and 1,2,3,4-tetrazolo[1,5-c]pyrimidines have been synthesized from 2-amino-3-cyano-7,7-dimethyl-7,8-dihydro-5H-pyrano[4,3-b]pyridine.     

Synthesis of 1- and 2-Carbamoylalkyl-2,3-dihydro-1H-indole and 9-Carbamoylalkyl-2,3,4,4a,9,9a-hexahydro-1H-carbazole Derivatives

Treatment of 1,2,3,9a-tetrahydro-9H-imidazo- and 1,2,3,4,10,10a-hexahydropyrimido[1,2-a]indol-2-one derivatives with formic acid gave 1-carbamoylalkyl-2,3,3-trimethyl-2,3-dihydro-1H-indoles. 9-Carbamoylmethyl- and 9-(2-carbamoylethyl)-4a-methyl-2,3,4,4a,9,9a-hexahydro-1H-carbazoles were prepared from 5,6,7,7a-tetrahydro-1H,4H-imidazo- and 1,2,6,7,8,8a-hexahydro-5H-pyrimido[2,1-k]carbazolones in a similar manner. Synthesis of 2-(2-carbamoylpropyl)-2,3,3-trimethyl-2,3-dihydro-1H-indole was carried out by reduction of 1,3-dihydrospiro[2H-indolo-2,2'-piperidine] derivative with Zn in acetic acid solution.     

Condensed isoquinolines 31. Reaction of 5-aryl-3-halo-12H-isoquino[2,3-a]quinazolines with electrophilic reagents

Treatment of 5-aryl-3-halo-12H-isoquino[2,3-a]quinazolines with electrophilic reagents readily forms their oxidation products. Acylation of the 3-chloro-5-phenyl-7,12-dihydroisoquino[2,3-a]quinazolinium perchlorate with Ac₂O in the presence of pyridine gave the product of electrophilic substitution at the C-7 atom 1-(3-chloro-5-phenyl-12H-isoquino[2,3-a]quinazolin-7-yl)-1-ethanone. By the same route phenacyl bromides react with the anhydro base 1 to give 5-aryl-7-(2-aryl-2-oxoethyl)-3-halo-isoquino[2,3-a]quinazolin-13-ium bromides. These salts readily react with nucleophilic reagents to form the products of addition at the C-12 atom. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1044–1052, July, 2008.