M. Sherif

The Chemistry of α-Haloketones and Their Utility in Heterocyclic Synthesis

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.

A convenient synthesis of thiazolopyrimidines, thiazolodipyrimidines and heterocyclothiazolopyrimidines

Abstract Ethyl 4-aryl-6-substituted-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates 1 reacted with bromomalononitrile (2) to give ethyl 3-amino-5-aryl-2-cyano-7-substituted-5H-thiazolo[3,2-a]pyrimidine-6-carboxylates 3. The latter compounds reacted with formic acid, hydroxylamine hydrochloride and with formamide to give 9H-3,4-dihydrothiazolo[3,2-a:4,5-b]dipyrimidine-8-carboxylates 5, 1H,8H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidine-7-carboxylates 8 and 2,7-diaminothiazolo[4,5-d]pyrimidine (7), respectively. Compounds 1b,e reacted with chloroacetyl chloride to yield ethyl 5-aryl-3-oxo-7-substituted-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylates 9a,b which coupled with arenediazonium chlorides to give the corresponding 2-arylhydrazone derivatives 10a,b. Compound 9a adds α-cyanocinnamonitriles 12a–c to yield ethyl 2-amino-4-aryl-3-cyano-9-(4-methoxyphenyl)-7-methyl-4H,9H-pyrano[2,3-d]thiazolo[3,2-a]pyrimidine-8-carboxylates 13a–c. Refluxing 1b–d with phenacyl bromide produced ethyl 5-aryl-7-methyl-3-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylates 14a–c.

β-enaminonitriles in heterocyclic synthesis: A novel synthesis and transformations of α-substituted-β-enaminonitriles

Abstract 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.

Heterocyclic synthesis with isothiocyanates : an expeditious synthetic route for polyfunctionally substituted 3-(thiazol-2'-ylidene)pyridines and their fused derivatives

Abstract 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.

NEW SYNTHESIS OF IMIDAZO[1,2-a]- AND PYRIMIDO[1,2-a]PYRIMIDINES

Abstract 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.

Studies on 2-Aminothiophenes: Synthesis, Transformations, and Biological Evaluation of Functionally-Substituted Thiophenes and Their Fused Derivatives

Abstract 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.

Synthesis and tautomeric structure of the azo-coupling products of 2 -methyl-7-phenylpyrimido[1,2-b][1,2,4 ]triazepine -4,9 (3h,5h)-dione

A simple synthetic strategy is described for synthesis of 3-arylazo-2-methyl-7-phenylpyrimido[1,2-b][1,2,4]triazepine-4,9-diones 4a–j. The acid dissociation constants were determined for the series prepared and were correlated by a Hammett-type equation using enhanced substituent constants. The results of such correlation together with the spectral data, including 15N isotopic labelling, indicated that the studied compounds exist predominantly in the hydrazone tautomeric form.

Synthesis and fungitoxicity of some pyrimidine derivatives

A series of 12 pyrimidine derivatives were prepared and testedin vitro against growth, sporulation and nucleic acid content ofFusarium oxysporum f. sp.lycopersici andHelminthosporium oryzae. Introduction of a thiazole ring together with two aryl groups into 2-aminopyrimidine brought about drastic toxicity for both fungi. Pyrimidine derivatives with aryl groups alone were less toxic. Nitro groups were found to enhance the toxicity of the pyrimidine derivatives especially when substituted in the ortho-position of the aryl groups. Inhibition of nucleic acid synthesis of both fungi was attributed mainly to the presence of the thiazole ring.

Preparation and Characterization of Biodegradable Polyurethane Nanocomposites Based on Poly(3-hydroxybutyrate) and Poly(Butylene Adipate) Using Reactive Organoclay

Polyurethane nanocomposites were synthesized using one-step solution polymerization of poly(3-hydroxybutyrate)-diol, poly(butylene adipate)-diol using 1,6-hexamethylene diisocyanate. Nanocomposites were prepared using an in-situ polymerization method. The structure was verified using FTIR and 1HNMR. Morphology was examined by XRD and TEM methods. Thermal properties were examined using DSC and TG. DSC showed that all samples were semicrystalline. The Cloisite 30B enhanced the melt crystallization of PHB segments while hindering those of the PBA segments. Thermal stability was improved compared to the neat PUs samples. The Coats-Redfern model was used to calculate the activation energy. Mechanical properties were improved with incorporation of organoclays.

Synthesis and antitumor screening of new 1,7-diphenyl-3-(1,3-disubstituted-1H-pyrazole-4-carbonyl)-[1,2,4]triazolo[4,3- a ]pyrimidin-5(1H)-ones

A new series of 3-(1,3-disubstituted-1H-pyrazole-4-carbonyl)-1,7-diphenyl-[1,2,4]triazolo[4,3-a]pyrimidin-5(1H)-ones 4 was prepared by reaction of the enaminone 2 with hydrazonoyl halides 3. The preliminary screening for antitumor activity of the synthesized compounds was carried out against Ehrlich Ascites Carcinoma tumor cells. The results revealed that the studied compounds 4 have low or no antitumor activity towards EAC tumor cells.