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A simple and efficient one-pot three-component synthesis of the title compounds (IV) is presented.

With a view to find new therapeutic agents against microbial infections, two novel series of tricyclic and monocyclic 5-(phenylazo)thiophene systems are synthesized starting from 3-amino-2-thioxopyrimidinone (III) and 2-cyanoacetamidothiophene (XII), respectively.

Various new compounds containing a thiazolopyrimidine scaffold as part of a tricyclic or tetracyclic framework are synthesized and evaluated for their antibacterial and antifungal activities.

The reaction of phenyl isothiocyanate with the active methylene reagents 1a–e gives the nonisolable 1:1 adducts 2a–e. The latter react with α-halogenated compounds, e.g. phenacyl bromide, bromoacetyl bromide, chloroacetone, chloroacetonitrile and some hydrazonoyl halides to give the corresponding polyfunctionally substituted 2,3-dihydrothiazoles or thiazolidinone ring systems.

The active methylene reagents 1a-d reacted with phenyl isothiocyanate in basic DMF at room temperature to yield the non-isolable 1:1 adducts 2a-d. In-situ cyclization of the latter with γ-bromoacetoacetanilides afforded the 2,3-dihydrothiazoles 3a-h. The reactivity of 3a towards a variety of chemical reagents has been undertaken. Thus, on smooth alkaline hydrolysis, with benzaldehyde and with benzenediazonium chloride, the thiazole derivatives 4, 5, 7 and 9 were obtained. With acetylacetone, malononitrile, ethyl cyanoacetate and cinnamonitriles it gave the corresponding thiazol-4-yl-pyridine derivatives 10, 11, 12, and 13 respectively. 13 Reacted with hydroxylamine hydrochloride and phenyl hydrazine to give the corresponding fused ring systems 15 and 17 respectively.

6-Aryl-4-oxo-2- thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitriles (1) reacted with bromomalo-nonitrile(2) to give 3-amino-7-aryl-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2,6-dicarbonitriles (3a-c). The latter compounds reacted with either formic acid, formamide or ammonium thiocyanate to yield the 7-aryl-9-oxo-4-substituted-thiazolo[3,2-a:4,5-d′]dipyrimidine-8-carbonitrile derivatives (4–6), respectively. Compounds (3a-c) could be converted into 7-aryl-3-amino-1-benzyl-5-oxo-5H-imidazo[1,2-a]pyrimidine-6-carbonitriles (8) and 4-amino-8-aryl-2,6-dioxo-3-substituted-1,2-dihydro-6H-pyrim-ido[1,2-a]pyrimidn-7-carbonitriles (9) by treatment in boiling ethanol with benzylamine and cyclic secondary amines, respectively.

Novel synthesis of α-substituted-β-enaminonitriles could be obtained from reaction of β-enaminonitriles with paraformaldehyde and dimethylamine. Such compounds reacted readily with a wide variety of reagents to give unique heterocyclic systems.

A novel synthesis of condensed pyridinethione carbocyclic glycosides utilizing pyridine-2(1H)thiones and α-bromoglucose or α-bromogalactose tetraacetate as starting components is described.

The reaction of phenyl isothiocyanate with the Knovenagel condensated active methylene compounds 1a-d gave the non-isolable salts 3a-d . The latter underwent in-situ heterocyclization on treatment with some halogenated compounds e.g. phenacyl bromide, ethyl bromoacetate δ-bromoacetoacetanilide, ethyl δ-bromoacetoacetate and δ-bromo-β-oxo-butyronitrile into the corresponding polyfunctionally substituted 3-(thiazol-2′-yliene)pyridine derivatives, which could also be annulated into fused heterocyclic ring systems. Chemical and spectroscopic evidences for the structure of the new compounds are described.

The active methylene compounds - derivatives of malonic or 4-oxobutanoic acid - reacted with carbon disulfide in dimethyl formamide containing potassium hydroxide to yield the non-isolable dipotassium disulfide intermediates. The latter were cyclized by α-haloketones to give thiophene, thieno[2,3- b ]thiophene, thieno[3,2- c ]pyrazole and thieno[3,2- b ]pyridine derivatives. The reactivity of the products toward various reagents was studied.

A convenientGewald synthesis of 3,5-diaminothiophene-2-carbonitrile derivatives (2) is reported. The synthetic potential of the β-enaminonitrile moiety in2 has been explored; it proved to be a promising candidate for the synthesis of polyfunctionally substituted thieno[3,2-b]pyridines and thieno[3,2-d]pyrimidines.

Phenylsulfonylacetophenones1 react with a mixture of elemental sulfur and malononitrile to yield the corresponding 2-amino-4-aryl-5-phenylsulfonylthiophene-3-carbonitriles2. Compound2a could be annelated to the corresponding thieno[2,3-d]pyrimidine and thieno[2,3-c]-pyrazole derivatives3 and5 upon reaction with nitrogen nucleophiles (cyanamide and hydroxylamine hydrochloride), respectively. The applicability and synthetic potency of5 to develop a facile convenient route to the polyfunctionally substituted thieno[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines8, 14, 17, 20, and21 is reported. Chemical and spectroscopic evidences for the structures of the new compounds are presented.

Starting from 2-benzoylbenzoic acid (1) and prototype hydrazine itself or some of its simple congeners produce phthalazin-1(2H)-one derivatives 2a–d. Reactions of 2 with P2S5 or POCl3 gave their th...

An expeditious synthetic route for the title precursor is reported. It provides access to a variety of polyfunctionally substituted pyridines, pyridazines, pyrazolopyridines, thiophenes, and thienopyridines.

The applicability and synthetic potency of novel reagent, 2-aryl-1,1-dicyano-3-(phenylsulfo-nyl)propenes 3 to develop an expeditious convenient synthetic route of unique polyfunctionally substituted carbocyclic and heterocyclic sulfone systems is reported. Chemical and spec­troscopic evidence for the structures of the newly synthesized compounds are described. Some of the obtained compounds were tested for their antimicrobial activity

This review focuses on the use of dimethylformamide dimethyl acetal in the preparation of heterocyclic compounds via formylation of active methylene groups, methyl groups to give enamines, and formylation of amino groups to give amidines. These compounds are found to be useful intermediates in the formation and modification of heterocyclic compounds. J. Heterocyclic Chem., (2009).

Heterocyclic enamines1 reacted with ethyl acetoacetate to afford the corresponding amide derivatives2. Treatment of2 with carbon disulphide yielded the dipotassium salts3which reacted in-situ with a variety of α -haloketones to give the respective substituted thiophenes5,8, and13. The reactivity of the latter products towards various chemical reagents was studied to yield their fused thiophene derivatives7,10,12, and14, respectively. Some representative compounds were tested for antimicrobial activity.

The molecular structures and spectral properties of α-haloketones as well as their syntheses are analyzed and reviewed. Their reactivity towards oxygen, nitrogen, and sulfur nucleophiles, carboxylic acids, carbon nucleophiles, alkenes, and alkynes are discussed.

Ethyl α-(3-carbamoyl-4,5,6,7-tetrahydrobenzo[b]thiophen-2-ylhydrazono)acetates 1 were prepared and established as previously described by our research group. Their reactivity toward a variety of active methylene reagents was studied to give pyran, pyridine, and pyridazine derivatives. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:300–306, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20019

2-Amino-4,5,6,7-tetrahydrobenzo[b]- thiophene-3-carboxamide (1) was prepared according to Gewald procedure. Its reactivity toward a variety of chemical reagents was studied to give thienopyridines and -pyrimidines. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:459–467, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10179

A novel synthesis of 2-thio-, and 2-oxo- and 2-methoxy-3-cyano-pyridine derivatives utilizing 2-furyl-methylene- and 2-thienylmethylene derivatives of acetophenone and activated nitriles as startin...

A novel one-pot synthesis of 3-bromomethylbenzo [d] isoxazole (3) utilizing o-hydroxy-α-bromoacetophenone is reported. Coupling of 3 with benzenediazonium chloride afforded, the first reported, C-(3-benzo [d] isoxazolyl)-N-(phenyl) formohydrazidoyl bromide (13). The chemical behaviour of 3 and 13 towards a variety of chemical reagents has been investigated