Simple and efficient one‐pot synthesis of 3,4‐dihydro‐2‐pyridones via solid‐supported Bi(III)nitrate catalyzed double michael addition‐azaannulation

4‐Aryl‐5‐carboethoxy‐6‐methyl‐2,3‐dihydro‐2‐pyridones were obtained, in high yield, by heating ternary mixtures of appropriate aldehydes, ethylacetoacetate and compounds possessing NH₂‐C=X functionality, in presence of immobilized Bi(III)nitrate and co‐catalyst Zn(II)chloride, under solventless conditions. The reaction proceeds smoothly at 140±5°C and seems to involve double Michael addition‐azaannulation.     

1,3‐Dipolar cycloadditions: Investigation of cycloadditions of c‐aryl‐n‐(4‐chlorophenyl) nitrones to n‐cinnamoyl piperidines

Investigation of cycloadditions of C‐aryl‐N‐(4‐chlorophenyl)nitrones to N‐cinnamoyl piperidines was carried out. Two diastereoisomeric and one regioisomeric cycloadducts, and in some cases ring‐opened compounds were characterized by spectroscopic and X‐ray data. Molecular modelling was carried out for conformational studies.     

1,3‐dipolar cycloadditions. Part XII ‐ selective cycloaddition route to 4‐nitroisoxazolidine ring systems

Cycloadditions of C,N‐diarylnitrones to β‐nitrostyrenes occurred to yield two diastereoisomeric cycloadducts, the 3,4‐trans‐4,5‐trans substituted isoxazolidine derivatives being formed selectively as the major products. These were characterised by spectroscopic and X‐ray data. Conformational studies were carried out by X‐ray crystallography and Molecular Modelling.     

Synthesis and characterization of a novel heterocycle: 1‐Substituted‐4‐arylazamethylene‐6‐arylpyrazolo[5,4‐d]‐1,3‐oxazine

A series of novel heterocycles 1‐aryl‐ or alkyl‐substituted‐4‐arylazamethylene‐6‐arylpyrazolo[5,4‐d]‐1,3‐oxazines were synthesized from the acylation of (5‐amino‐1‐substituted‐pyrazol‐4‐yl)‐N‐carboxamide in 63‐89% isolated yields at room temperature within 12 hours. The structure was confirmed by X‐ray crystal analysis.     

Diverse reactivity of α‐carbanions derived from alkylidenephosphoranes toward 2‐(1λ5‐diazynylidene)‐1H‐indene‐1,3‐(2H)dione. General approach to conjugated oxadiazines,pyridazines and spiro[3]pyrazoles

Different types of phosphonium carbanions were applied to 2‐diazonio‐1,3‐dioxo‐2,3‐dihydro‐1H‐inden‐2‐ide ( 1 ) in order to synthesize a number of condensed and fused N‐heterocycles. When 1 was treated with cyanomethyltriphenylphosphonium chloride oxadiazine‐, and pyridazine derivatives were obtained whereas bis‐indanylidene derivatives resulted from the reaction of 1 with methyl_ and ethyltriphenylphosphonium bromides. On the other hand, a series of substituted and unsubstituted spiro[3′]pyrazoles were obtained from the di azo substrate when reacted with vinyl_and allyltriphenylphosphonium bromides.     

Synthesis of some 2‐oxo and 2‐thioxo substituted pyrimidines using solvent‐free conditions

A series of oxo‐ and thioxopyrimidines 4 ( a‐m ) were synthesized by one‐pot three components cyclocondensation reaction of β‐ketoester, aldehyde and urea/thiourea using benzyltriethylammonium chloride as a catalyst under solvent‐free conditions. The yields of products following recrystallization from ethanol were of the order of 65‐87%. IR and ¹HNMR spectroscopy and elemental analysis were used for identification of these compounds.     

Preparation of 4,5‐dihydro‐1,3‐selenazoles by reaction of aromatic primary selenoamides with acetylenedicarboxylate

Reactions of primary selenoamides with dimethyl acetylenedicarboxylate afforded 2‐aryl‐5‐methoxy‐carbonylmethylene‐4,5‐dihydro‐1,3‐selenazol‐4‐ones in moderate to high yields. Reactions of the primary selenoamides with acetylenedicarboxylic acid gave 2‐aryl‐5‐carboxymethylene‐4‐ethoxy‐4,5‐dihydro‐1,3‐selenazol‐4‐ols in moderate yields.     

Transformations of phenylhydrazones of 5‐acyl‐1,2,4‐triazines to pyrazolo[4,3‐e][1,2,4]triazines or 4‐cyanopyrazole

A simple and high yielding preparation of pyrazolo[4,3‐e][1,2,4]triazines and 4‐cyano‐3‐methyl‐1‐phenylpyrazole derivatives from corresponding phenylhydrazones of 5‐acyl‐1,2,4‐triazines by melt under acidic medium and by thermal heating, respectively.