Volume 22, Issue 2

The convenient synthesis of a series of 3-phenylpyrido[1,2- a ]pyrimidinones 4 , 3-phenylpyrimido[1,2- c ]quinazolinones 7 and 3-phenylpyrazino[1,2- a ]pyrimidinones 10 with promising biological activity is presented.

An efficient three-component synthesis of o -hydroxyphenyl-substituted pyrazolo[3,4- b ]pyridines from substituted salicylic aldehydes, β -keto esters and 5-aminopyrazoles in the presence of FeCl 3 is presented. Newly synthesized compounds were fully characterized by means of 1 H NMR, 13 C NMR, IR, HRMS and elemental analysis.

Claisen-Schmidt condensation of ferrocenecarboxaldehyde ( 2b ) with 2-acetylfuran ( 4 ) yielded (E) -3-ferrocenyl-1-(2-furyl)prop-2-en-1-one ( E -5 ) together with 1,5-di(2-furyl)-3-ferrocenylpentane-1,5-dione ( 6 ). Reactions of the ferrocenyl chalcones 3a,b and 5 with hydrazine hydrate, phenyl hydrazine, ethyl acetoacetate, ethyl cyanoacetate and malononitrile, were also studied. Possible reaction mechanisms were discussed and structures of the new products were unambiguously characterized by common analytical and spectroscopic methods.

A facile access to 3-alkyl-5- N -allylamino-2- N ′-benzoylimino-1,3,4-thiadiazoles via Dimroth rearrangement is reported. Alkylation of 5-allylamino-4-benzoyl-1,2,4-triazole-3-thione with alkyl halides in basic alcohol solution is regioselective. A mechanism for the formation of a 1,3,4-thiadiazole ring by 1,2,4-triazole recyclization is proposed. The obtained compounds were characterized by NMR, elemental analysis and X-ray diffraction analysis.

Synthesis and catalytic activity of chiral ligands 5,6-diphenyl-3-{3-[(4 S/R )-4-R/Ar-4,5-dihydro-1,3-oxazol-2-yl]pyridin-2-yl}amino-1,2,4-triazines 2 and their analogs 3 possessing an N -oxide function in the pyridine ring are described. The pivotal step in the synthesis of ligands 2 is the Buchwald-Hartwig Pd-catalyzed cross-coupling reaction between 3-bromo-5,6-diphenyl-1,2,4-triazine ( 7a ) and enantiopure 3-(4,5-dihydro-1,3-oxazol-2-yl)pyridin-2-amines 6a – d . Aromatic nucleophilic substitution of chlorine in 3-chloro-5,6-diphenyl-1,2,4-triazine ( 7b ) with 3-(4,5-dihydro-1,3-oxazol-2-yl)pyridin-2-amine 1-oxides 12 was investigated as the key reaction in the synthesis of ligands 3 . Two undesired derivatives 13 or 14 , resulting from unexpected reactions of 3 , were isolated depending on reaction conditions. Compounds 2 and 3 as well as the side products 13 and 14 were screened as chiral ligands in the copper catalyzed enatioselective nitroaldol reaction.

Michael addition reactions of O -nucleophiles to C(3) exocyclic nitromethylene derivative of diacetone glucose are reported. The reactions with primary alcohols proceed at ambient temperature in the presence of different bases with good yields and give products with excellent diastereoselectivity. The addition of the nucleophile occurs from the β-face of the carbohydrate as shown by single crystal X-ray analysis. The reactions with secondary alcohols give low yields of products while phenolic compounds do not react. Under certain conditions, isomerization of starting material is observed.

New synthesis of 1-alkyl-1 H ,1′ H -2,2′- bibenzo[ d ]imidazoles 3 by alkylation of a disodium derivative of 1 H ,1′ H -2,2′-bibenzo[ d ]imidazole 2a with alkyl halides is proposed. It is noteworthy that 1,1′-dialkylated byproducts 4 are formed in yields of <5%. The structure of all obtained compounds has been confirmed by 1 H NMR, 13 C NMR, and HRMS or elemental analysis.

Treatment of isoquinolinecarboxamide 4a with triethyl orthoformate, chloroacetyl chloride or carbon disulfide afforded the pyrimidinone 7 , oxopyrimidinethione 12 and chloromethylpyrimidinone 18 , respectively. These products were used as versatile starting materials for synthesis of other heterocyclic compounds. The heterocyclic hydrazide 6 was also obtained.

This article deals with spectrophotometric and ab initio studies of 1,3-diethyl-7-hydroxy-5,5,7-trimethyl-2-thioxo-1,2,3,5,6,7-hexahydro-4 H pyrano[2,3- d ]pyrimidin-4-one (HDEAC). Acid-base properties for I = 0.25 and in a strongly acidic solution of HCl (I → 0) were investigated. The obtained value of pK a (5.79±0.02) and -pK H (1.68±0.03) show that this compound is a weaker acid than thiobarbituric acid. For interpretation of the spectrophotometric data the ab initio methods with density functional theory at level PBE0/cc-pVDZ/SMD were used. The most energetically favorable structures for neutral and cationic forms of HDEAC were proposed.