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).     

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 of imidazoisoindol-3-ones by a palladium-catalyzed intramolecular C-H insertion reaction

A simple protocol for the synthesis of various imidazoisoindol-3-ones is described by employing a palladium-catalyzed intramolecular C-H insertion reaction of substituted 2-haloaryl imidazolin-2-ones.     

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.     

Microwave-assisted N-Boc deprotection under mild basic conditions using K3PO4·H2O in MeOH

A simple and efficient method for the deprotection of secondary Boc-protected amino compounds under mild basic conditions using K₃PO₄·H₂O in MeOH assisted by microwave irradiation has been presented.     

A <Emphasis Type="Italic">p</Emphasis>-methoxybenzyl (PMB) protection/deprotection approach toward the synthesis of 5-phenoxy-4-chloro-<Emphasis Type="Italic">N</Emphasis>-(aryl/alkyl) thiophene-2-sulfonamides

The synthesis of 17 phenoxy substituted 4-chloro-N-(aryl/alkyl)thiophene-2-sulfonamides using a PMB protection/deprotection strategy is described. Nucleophilic displacement of p-methoxybenzyl (PMB) protected 4,5-dichloro-N-(aryl/alkyl)-thiophene-2-sulfonamides was carried out with different phenols under mild basic conditions. Reaction times of 3–6 h and overall yields of 78–98% were achieved with the PMB group in place compared to no reaction without this protecting group. The PMB group was easily and selectively removed in 68–98% yield using TFA in DCM.     

Diastereoselective Reformatsky reaction of methyl 4-bromocrotonate with 1,2:5,6-di-O-isopropylidene-α-d-ribo-hexofuranos-3-ulose: application to novel bicyclic nucleosides

This paper describes an efficient synthetic route for novel bicyclic nucleosides. The stereochemistry of the targeted bicyclic nucleosides was successfully achieved by vinylogous Reformatsky reaction and ring closing metathesis reaction on a carbohydrate backbone.     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。     

Liebeskind-Srogl cross coupling mediated synthesis of verbenachalcone

A flexible and scalable total synthesis of verbenachalcone is achieved in eight linear steps from cheap commercially available starting material, 3-(4-hydroxyphenyl)propanoic acid.     

In silico targeting PAD4 for the treatment of rheumatoid arthritis

Structural Chemistry - Rheumatoid arthritis (RA) is an autoimmune disorder that causes chronic inflammation with periodic bursts of activity in multiple synovial joints which lead to irreversible...