Robert K. Smalley

Heterocycles by intramolecular aza-Wittig reactions of iminophosphoranes obtained from 2-azidobenzoyl- and 2-azidobenzylidene derivatives

Abstract Iminophosphoranes have been used in intramolecular aza-Wittig reactions to prepare pyrrolo[1,2-a]benzimidazoles, fused quinazolinones, quinolines, and an isoindolo[1,3,4]benzotriazepinone.

3H-azepines and related systems. Part 4. Preparation of 3H-azepin-2-ones and 6H-azepino[2,1-b]quinazolin-12-ones by photo-induced ring expansions of aryl azides

Abstract Photolysis of a series of p-substituted phenyl azides (p-X-C6H4N3; X= CO2Me, CO2Et, CN, CF3, SO2NH2, CO2CHPh2, COMe, CHO, and NO2) in 1:1 (v/v) THF-water solution produces, in the majority of cases, a 5-substituted-3 H -azepine-2-one. In a like manner, 3 H -azepin-2-one-3-carboxylates can be prepared from 5-substituted-2-azidobenzoates, providing the 5-substituent is electron-withdrawing. 3 H -Azepin-2-one mono- and di-carboxylic acids, the former in admixture with decarboxylated material, and 6 H -azepino[2,1-b]quinazolin-12-ones, are obtained by irradiation of 2-azidobenzoic acid and of 5-azidoisophthalic acid, respectively. The mode of formation of the azepino-quinazolinones is discussed.

Base-induced intramolecular cyclisation of o-azidophenyl sec-alkyl ketones. A new synthesis of 2,2-dialkylindoxyls

Abstract o -Azidophenyl sec -alkyl ketones in ethanolic potassium hydroxide at room temperature cyclise in high yield to 2,2-dialkylindoxyls.

3H-Azepines and related systems. Part 5. Photo-induced ring expansions of o-Azidobenzonitriles to 3-Cyano- and 7-Cyano-3H- azepin-2(1H)-ones

Abstract Unlike other aryl azides bearing electron-withdrawing ortho-substituents, o-azidobenzonitriles on photolysis in aqueous-tetrahydrofuran yield mixture of the expected 3-cyano- and the unexpected 7-cyano-3H-azepin-2(1H)-ones. In one instance ring-contraction to a 2-azabicyclo[3.2.0]hept-6-ene-3-one is noted. X-Ray crystallographic data for 7-cyano- and 4-chloro-7-cyano-3H-azepin-2-one, and for the azabicycloheptenone, are presented.

1,3-dipolar cycloadditions of 2-ethoxy- and 2-(ethylthio)-1-azetines with nitrile oxides, nitrile ylides and nitrilimines : an unexpected 1,2,4-triazole formation

Abstract 2-Ethoxy- and 2-(ethylthio)-1-azetines readily undergo 1,3-dipolar cycloadditions with nitrile oxides and nitrile ylides to give stable 4,5-bicyclic cycloadducts. With nitrilimines, however, the expected 1,3-dipolar cycloadducts and/or unexpected ring-opened products, namely 1,2,4-triazoles, are formed depending on the nature of the nitrilimine N -substituent. In contrast, the azetines fail to react with nitrile sulphides, azomethine ylides, nitrones, aryl azides, and various dienes. X-ray crystallographic data on the nitrile oxide, nitrile ylide, and nitrilimine cycloadducts, and on the 1,2,4-triazoles, are presented. Also a mechanistic rationale for triazole formation is offered.

Thermal rearrangement of some 3-substituted-2,1-benzisoxazoles

Abstract 3-(Phenyliminomethyl)- and 3-arylazo-2,1-benzisoxazoles undergo thermal rearrangement to 3-phenylquinazolin-4-one and 3-aryl-1,2,3-benzotriazin-4-ones, respectively.

1,3-Dipolar cycloadditions of 2-ethoxy- and 2-(ethylthio)-1-azetines with nitrilimines

Abstract 1,3-Dipolar cycloadditions of diphenylnitrilimines with 2EtO-and 2EtS-tetramethyl-1-azetines (1a,b) are accompanied by ring-opening and loss of EtXH (X = O or S) to give 1,2,4-triazoles (3), whereas with N-(4-nitrophenyl) nitrilimines the expected cycloadducts and/or ring-opened products are formed.

2-(1,2-Dihydro-3-oxo-4,5-diphenyl-3H-pyrrol-2-ylidene)-1,2-dihydro-4,5-diphenyl-3H-pyrrol-3-one: A new pyrrole-based indigotin analogue

Abstract Thermolysis, in boiling o-dichlorobenzene, of the cycloadducts 5 and 10a,b of diphenylcyclopropenone and 2-(alkylthio)azetines 4 and 9a,b yield the title compound 8.

Base-induced intramolecular cyclisation of N-(o-azidobenzoyl)-arylamines. A new synthesis of 2-aryl-1,2-dihydro-3H-indazolin-3-ones

Abstract In strong base, e.g., sodium hydride in dimethylformamide, N -( o -azidobenzoyl)arylamines cyclise in high yield to 2-aryl-1,2-dihydro-3 H -indazolin-3-ones.

1H- and 2H-indazoles by thermal and photolytic decomposition of o-azidobenzoic acid and o-azidobenzaldehyde derivatives

Ethyl o-azidobenzimidate (6) and o-azidobenzamidine (7) on thermolysis yield 3-ethoxy-(9; X = OEt) and 3-amino-1H-indazole (9; X = NH2), respectively. The former product is also obtained on irradiation of the imidate in methanol–tetrahydrofuran solution.2-Aryl- and 2-heteroaryl-3-chloro-2H-indazoles have been prepared by the action of hot thionyl chloride on o-azidoanilides. The trichloro-2H-indazoles obtained by the action of phosphorus pentachloride on o-azidobenzanilide (12) and by the action of thionyl chloride on N-(o-azidobenzoyl)-2-aminopyridine have been identified as the 3,5,7-trichloro derivatives. The reductive dehalogenation, nitration, and reactivity of the halogen towards nucleophiles, of 3-chloro-2-phenyl-2H-indazole (19) are reported.A new practicable synthesis of o-azidobenzaldehyde (31; X = O) is described. Thermolysis of its phenylhydrazone and semicarbazone derivatives yields 2H-indazoles.