The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Zirconyl chloride promoted highly efficient solid phase synthesis of amide derivatives

An efficient solid phase route for the synthesis of amide derivatives by the reaction of carboxylic acids with urea in the presence of catalytic amount of zirconyl chloride under microwave irradiation conditions was described.In this way,a range of interesting amide derivatives was obtained in good to excellent yields.The catalyst was recycled with fresh reactants and it gave almost similar results without significant loss of activity up to the third run.     

Cerium(Ⅳ) ammonium nitrate catalysed facile and efficient synthesis of polyhydroquinoline derivatives through Hantzsch multicomponent condensation

A general and convenient practical approach for the synthesis of polyhydroquinoline derivatives has been achieved via one-pot four-component Hantzsch condensation of aromatic aldehydes,dimedone,ethyl acetoacetate and ammonium acetate in the presence of a catalytic amount of cerium(Ⅳ) ammonium nitrate (CAN),in ethanol solvent at ambient temperature.Simple work-up,mild reaction conditions,inexpensive and non-toxic catalyst,and excellent product yields are the advantageous features of this method.     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Synthesis and antimicrobial study of linked heterocyclics containing Pyrazole-pyrimidine-thiazolidin-4-one

A new series of linked heterocyclics, 3-[4-(4-chlorophenyl)-6-(3,5-dimethyl-1-phenyl-1H-4-pyrazolyl)-2-pyrimidinyl]-2-(aryl/heteryl)-1,3-thiazolan-4-ones (6a-j), has been synthesized by the one-pot cyclo-condensation of 4-(4-chlorophenyl)-6-(3,5-dimethyl-1-phenyl-1H-4-pyrazolyl)-2-pyrimidinamine (5), aryl/heteroaryl aldehyde and thioglycolic acid. The structures of the synthesized compounds have been confirmed via IR, (1)H-NMR, (13)C-NMR, MS and elemental analyses. Further, all the newly synthesized compounds 6a-j have been assayed for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi. The compounds containing moieties like 4-nitrophenyl (6c), 3-nitrophenyl (6d), 4-dimethylaminophenyl (6g), 2-furyl (6i) and 1,3-benzodioxole (6j), at 2-position of thiazolidin-4-one ring exhibited good inhibitory activity against all the tested organisms.     

Synthesis of some new 3-[5-(2-oxo-2H-3-chromenyl)-1,3-oxazol-2-yl]-1,3-thiazolan-4-ones as antimicrobials

<正>A series of some new 2-imino-5-[(Z)-1-(4-methylphenyl)methylidene]-3-[5-(2-oxo-2H-3-chromenyl)-1,3-oxazol-2-yl]-1,3- thiazolan-4-ones 5a-j has been synthesized and assayed for their antibacterial activity against Gram-positive bacteria viz.Bacillus subtilis(ATCC 6633),Staphylococcus aureus(ATCC 6538p) and Micrococcus luteus(IFC 12708),and Gram-negative bacteria viz. Proteus vulgaris(ATCC 3851).Salmonella typhimurium(ATCC 14028) and Escherichia coli(ATCC 25922).Among the screened compounds,5d,5e,5f,5g,and 5j exhibited potent inhibitory activity compared to standard drug,and emerged as potential molecules for further development.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8′‐methylene‐bis‐4‐oxo‐1H and 2H‐chromeno[4,3‐C]pyrazoles

The ethyl ester of 5,5′‐methylene‐bis‐salicyclic acid 3 was prepared by the esterification of 5,5′‐methylene‐bis‐salicylic acid 2 . The compound 3 on reacting with ethylacetoacetate yields 6,6′‐methylenebis‐(3‐acetyl‐4‐hydroxycoumarin) 4 . The compound 4 was regioselectively converted into either 8,8′‐methylene‐bis‐(4‐oxo‐1H‐chromeno[4,3‐c]pyrazoles) 6 or 8,8′‐methylene‐bis(‐4‐oxo‐2H‐chromeno[4,3‐c]‐pyrazoles) 7 under microwave irradiation. High yields are achieved even on a gram scale, while reaction times are considerably shortened compared to conventional heating conditions.     

Knoevenagel condensation of α,βunsaturated aromatic aldehydes with barbituric acid under non-catalytic and solvent-free conditions

An efficient route for the synthesis of 5-(arylpropenylidine)-2,4,6-pyrimidinetrione 3 from an appropriateα,β-unsaturated aromatic aldehydes 1 and barbituric acid 2 under both non-catalytic and solvent-free microwave irradiation conditions was described.In this way,a range of biologically important compounds 3 was obtained in good to excellent yields (86-98%) in a very short reaction time (30-80s).