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Sn exchanged HBeta zeolite was prepared and characterized by PXRD, surface area, TPD and TEM analysis. The Sn exchanged zeolite was found to be highly efficient catalyst for the direct synthesis of α-amino nitrile from various ketones and aldehydes with amine and trimethyl silylcyanide (TMSCN) under solvent-free condition. Excellent yield of α-amino nitrile (up to 96%) was achieved within 10–120 min at room temperature. The Sn exchanged HBeta zeolite was recovered and reused several times without the loss of its catalytic performance.

The reactions of 2-(4,5-dihydrothiazol-2-ylthio)-1-arylethanone with different nucleophiles including semicarbazide hydrochloride, hydroxylamine hydrochloride, hydrazine, ethylenediamine and aminoethanol have been investigated, and the formation of a variety of products with different reagents is highlighted.

Fe(Cp) 2 PF 6 (5 mol %) efficiently catalyzed Mannich reaction of aldehydes, anilines, and ketones under solvent-free condition to give β-amino-ketones in high yield (up to 94%) within 30 min with anti -isomer in excess. Simple experimental conditions and product isolation procedure makes this protocol potential for the development of clean and environment-friendly strategy for the synthesis of β-amino-ketones.

The reaction of hydroxylamine hydrochloride with ethyl 3‐aroyl‐1‐cyano‐4‐hydroxy‐2,4,6‐triarylcyclohexanecarboxylate has led to the formation of ethyl 2‐[amino(hydroxyimino)methyl]‐3‐aryl‐5‐(hydroxyimino)‐5‐arylpentanoate via a tandem ring opening and oximation process. The structures of the products are confirmed by NMR and X‐ray techniques, and the conformational features of the product arrived at are compared with a molecular dynamics simulation study.

Synthesis of novel 1,2,3-selena/thiadiazoles, linked to different benzo-1,3-heteroazole ring by sulfur has been reported. Structural features of the compounds have been analyzed by 1H and 13C NMR, mass and single crystal X-ray studies.

The synthesis and characterization of a new set of selenadiazoles, 3-aryl-3-(4-aryl-1,2,3- selenadiazol-5-yl)-2-phenyl-2-propenenitrile derived from corresponding semicarbazones have been reported. The structural features of selenadiazoles synthesized have been analyzed by 1 H NMR, 13 C NMR and X-ray techniques.

The chemoselective reaction of hydrazine on the ketone rather than the ester in a gem diester system with a γ‐keto group by hydrazinium sulfate and a tandem deesterification of one of the esters in this system by N,N‐dimethylformamide are reported.

The conformational features of diethyl 2-[3-{2-(aminocarbonyl)hydrazono}-1-(4-methoxyphenyl)-3-phenylpropyl]malonate are analysed in solid and solution states in the light of the diastereotopic characteristics, and compared with that of {3-[4-( N , N -dimethylamino)phenyl]-1-(4-methylphenyl)-3-(phenylsulfanyl)propylidene} semicarbazide.

The title compound, C17H17N5OS, adopts the configurations Z around the imine C=N bond and E around the C(O)—NH bond. The configurations are stabilized by two intra­molecular N—H⋯N hydrogen bonds. In the crystal structure, mol­ecules are linked together by N—H⋯O hydrogen bonds, forming a three-dimensional network.

This article describes the acetic anhydride induced rearrangement of nitrone to amide and the addition of Grignard reagent to the nitrones yielding substituted hydroxylamines. It has been found that the conversion of C-phenyl-N-(1-methyl2-aryl)ethyl nitrones 1 to N-(1-methyl-2-arylethyl)arylcarboxamides 2 is clean, selective and quantitative under solventless condition with microwave irradiation. The Grignard addition on nitrones 1 with phenylmagnesium bromide has been found to be very effective giving hydroxylamine derivatives quantitatively. All the synthesised compounds have been fully characterized by NMR and single crystal X ray analysis.

In the title compound, C25H28N4OS, the benzene rings are nearly perpendicular to the central C—C—C—S linkage, whereas the semicarbazide plane forms a dihedral angle of 67.7 (1)° with the central linkage. In the crystal structure, inversion-related mol­ecules exist as N—H⋯O hydrogen-bonded dimers.

A first approach for catalytic asymmetric Strecker reaction of aldehydes with a secondary amine in the presence of sodium fluoride using hydroquinine as chiral catalyst was developed. The catalytic system gave α-aminonitriles in excellent yields (up to 95%) and high enantioselectivities (er up to 94:6). The efficacy of the chiral product was successfully fulfilled in the improved synthesis of (S)-clopidogrel (an antiplatelet agent).

Recyclable chiral amide-based organocatalyst 5 efficiently catalyzed asymmetric Strecker reaction of various aromatic and aliphatic N-benzhydrylimines with ethyl cyanoformate as cyanide source at −10 °C to give a high yield (95%) of α-aminonitriles with excellent chiral induction (ee, up to 99%) with the added advantage of recyclability. Based on experimental observations a probable mechanism was proposed for this reaction. This protocol with catalyst 5 was extended for the synthesis of (R)-phenylalanine and pharmaceutically important drug intermediate (R)-3-phenylpropane-1,2-diamine in high yield with high enantioselectivity.

Fe(Cp) 2 PF 6 (5 mol %) efficiently catalyzed Mannich reaction of aldehydes, anilines, and ketones under solvent-free condition to give β-amino-ketones in high yield (up to 94%) within 30 min with anti -isomer in excess. Simple experimental conditions and product isolation procedure makes this protocol potential for the development of clean and environment-friendly strategy for the synthesis of β-amino-ketones.

The chemoselective reactions of selenium dioxide with differently substituted adducts generated by 1,4-addition on benzylidene acetophenone are described. This reaction has been shown to be dependent on the nature of the substituent present, leading to different products by α-oxidation/α-oxidation followed by dehydrogenation/dehydrogenation, enolization, and cyclization.

The synthesis and characterization of new 5-(2-nitro-1-arylpropyl)-4-aryl-1,2,3-selenadiazoles, obtained from the α-functionalised semicarbazones are described. The structures of these compounds have been established by 1 II and 13 C NMR spectral data.

A novel method for the synthesis of 1,3-enynes is described through oxidative cyclization of the semicarbazones of Michael adducts having potential nitrile functionality. Reaction of these 1,3-enynes with diaryl nitrones has yielded a diastereomeric mixture of highly substituted 2,3-dihydro-1H-pyrrole derivatives via a tandem regioselective addition with subsequent rearrangement.

An efficient solventless synthesis of alpha-aryl-N-1-methyl-2-(2/4-chlorophenyl)]ethyl nitrones has been achieved in excellent yield. The compounds are characterized by NMR and X-ray studies. The antimicrobial activities of the synthesized compounds have also been investigated.

The reaction of hydroxylamine hydrochloride with ethyl 3‐aroyl‐1‐cyano‐4‐hydroxy‐2,4,6‐triarylcyclohexanecarboxylate has led to the formation of ethyl 2‐[amino(hydroxyimino)methyl]‐3‐aryl‐5‐(hydroxyimino)‐5‐arylpentanoate via a tandem ring opening and oximation process. The structures of the products are confirmed by NMR and X‐ray techniques, and the conformational features of the product arrived at are compared with a molecular dynamics simulation study.

A novel method for the synthesis of 1,3-enynes is described through oxidative cyclization of the semicarbazones of Michael adducts having potential nitrile functionality. Reaction of these 1,3-enynes with diaryl nitrones has yielded a diastereomeric mixture of highly substituted 2,3-dihydro-1H-pyrrole derivatives via a tandem regioselective addition with subsequent rearrangement.

The chemoselective reaction of hydrazine on the ketone rather than the ester in a gem diester system with a γ‐keto group by hydrazinium sulfate and a tandem deesterification of one of the esters in this system by N,N‐dimethylformamide are reported.

The 1,3-tautomerism associated with 2-(2-hydroxy-5-substituted-aryl)benzimidazoles was studied in different solvents. The effect of hydrogen bonding involving the hydroxyl group of the 2-aryl ring on the tautomerism was investigated using NMR spectroscopy. The influence of the solvent concentration on 2-(2-hydroxy-5-chloroaryl)benzimidazole was studied in acetone-d6 and DMSO-d6. Copyright © 2005 John Wiley & Sons, Ltd.