Chemistry and heterocyclization of thiosemicarbazones

The review summarizes the literatures dealing with the synthesis of thiosemicarbazone derivatives, chemical reactions and their applications in the synthesis of important heterocyclic as well as fused heterocyclic compounds J. Heterocyclic Chem., (2012).     

Reactions of 1-cyanazoles with carbohydrazides

(N″-acyl)azole-1-carbohydrazonamides were synthesized by the reaction of 1-cyanazoles with carbohydrazides. The yield of the final reaction products was shown to depend on the structure of the hydrocarbon radical in the carbohydrazide.     

Symmetrical spiro-phosphoroheterocycles from the selenation of carbohydrazides

2,4-Bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (Woollins’ reagent) reacts with benzoic hydrazides in refluxing toluene to give new symmetrical spiro heterocycles in 48-76% isolated yields. However, under identical conditions, treating Woollins’ reagent with thiophene-2-carbohydrazide leads to an additional product, 1,3,4-selenadiazole (27% yield) together with the spiro phosphorus heterocycle in 44% yield. Three representative X-ray structures are reported.     

Synthesis and heterocyclization of N-phenylaminolactams

Intramolecular alkylation of N-phenylhydrazides of -chlorovaleric and -chlorocaproic acids was used to prepare the corresponding N-phenylaminolactams. Their reaction with phosphoryl chloride formed the corresponding condensed tricyclic systems of tetrahydro--carbolines and azepino[2.3-b]indole. 3-b]indole.All-Russian Scientific Center for the Safety of Biologically Active Substances (VNTs BAV), Kupavna, Moscow Oblast, 142450. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1507–1510, November, 1995. Original article submitted June 9, 1995.     

Thiosemicarbazides in heterocyclization

This review summarizes the preparation of substituted thiosemicarbazides with their application with synthesis of important linear and heterocyclic compounds. J. Heterocyclic Chem., (2011).     

Aminonaphthoquinones in heterocyclization

Because of the interesting biological activities of aminonaphthoquinones, in this review we survey two classes of amino‐1,4‐naphthoquinones: 2,3‐diamino‐1,4‐naphthoquinone and 2‐amino‐1,4‐naphthoquinone. The review includes synthetic methodologies for these classes in addition to their heterocyclization processes. J. Heterocyclic Chem., (2012).     

Dicyanomethylene compounds and heterocyclization of acylthiosemicarbazides

(1,3‐Dioxo‐2,3‐dihydro‐1H‐inden‐2‐ylidene)propanedinitrile ( 1 , in ethyl acetate solution), 3‐(dicyano‐methylene)‐2‐indolone ( 2 , in ethanol/piperidine solution) and 7,7′,8,8′‐tetracyanoquinodimethane ( 3 , in pyridine solution) act on substituted acylthiosemicarbazides 4a‐d , forming the derivatives of oxoindeno‐pyrrolylidenehydrazide ( 5a‐d and 7a‐d ), thiazoloindolylidenehydrazide ( 12a‐d ), pyrroloindolylidene‐hydrazide ( 13a‐d ) and spiro[pyrrolylidene‐4,1′(cyclohexa‐2′,5′‐dienylidene)]propanedinitrile ( 18a‐d ). Rationales for these conversiones involving the nucleophilic addition on dicyanomethylene carbon atom are presented.     

Base-catalyzed intramolecular heterocyclization of o-alkynylbenzhydrazides

The reaction of methyl o-(2-R-ethynyl)benzoates with hydrazine affords either fused 4-R-methylphthalazin-1-ones or 2-amino-3-R-methylideneisoindolin-1-ones. The latter are on treatment with KOH undergo recyclization into the corresponding 4-R-methylphthalazin-1-ones.     

Direct heterocyclization of benzocrown ethers

The synthesis of novel 3,3‐dialkyl‐3,4‐dihydroisoquinoline derivatives via direct heterocyclization of benzocrown ethers is described. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:192–195, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20092     

Studies on heterocyclization of acetoacetanilide

Base-induced cyclocondensation of acetoacetanilide (1) and benzoyl isothiocyanate (2) afforded mercaptopyridine (4). Compound 4 reacted with NaOCl in presence of NH₄OH/NaOH to produce isothiazolopyridine (6). Heterocyclization of 4 by ethyl bromoacetate and/or phenacyl bromide afforded pyridothiazapene and pyridine derivatives 7, 8, respectively. The synthesis of pyrazolopyridine (9) was achieved by reaction of 4 with hydrazine hydrate. Oxidative cyclization of 4 by Br₂ produced isothiazolopyridine (10). Chlorination of compound 4 yielded isothiazolopyridine dioxide (11). Compound 1 transformed into pyrane derivatives 12 and 13 by reaction with benzylidenemalononitrile and benzylideneacetophenone, respectively. Heterocyclization of compound 1 by ethylcyanoacetate and diethyloxalate afforded pyridine and cyclopentane derivatives 14 and 15, respectively. Compound 1 heterocyclized to indenopyrane (16) or indenopyrrole (17) upon reacted with ninhydrin on cold and hot condition, respectively. Heterocyclization of compound 1 and benzilmonohydrazone afforded pyridazine derivative 18. Coupling of 1 with diazonium salt afforded hydrazone 19 which cyclized using CS₂/KOH gave pyridazine derivative 20.     

Unexpected heterocyclization of 1,4-naphthoquinone thioglucosides

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, p. 2899, December, 1991.     

Synthesis and heterocyclization of osazones of carbonyl-substituted glyoxals

Enolates of α-chloro-β-oxoaldehydes react with arylhydrazines in the presence of acetic acid, forming osazones of carbonyl-substituted glyoxals. The same osazones are obtained by the reaction of β-oxo-α-chlorenamines with arylhydrazines. Under conditions of acid catalysis, these osazones undergo intramolecular heterocyclization to the corresponding functionalized pyrazoles. Kazan' State Technological University. Kazan' 420015, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 190–193, February, 1998.     

Silver assisted heterocyclization of acetylenic compounds

Silver assisted heterocyclization of acetylenic alcohols or acids provides an easy and mild access to α-methylene oxygenated heterocycles.