نتایج جستجو برای: regioselectivity

تعداد نتایج: 1520  

Journal: :Chemical communications 2013
Marc Garcia-Borràs Sílvia Osuna Marcel Swart Josep M Luis Miquel Solà

In this work we show that the regioselectivity of the Diels-Alder, 1,3-dipolar, and carbene cycloadditions to C(60) changes from the usual [6,6] addition in neutral species to the [5,6] attack when the number of electrons added to the fullerenic cage increases. Changes in the aromaticity of the five- and six-membered rings of C(60) during the reduction process provide a rationale to understand ...

Journal: :Journal of the American Chemical Society 2009
Xiao-Hua Chen Qiang Wei Shi-Wei Luo Han Xiao Liu-Zhu Gong

The privileged spiro[pyrrolidin-3,3'-oxindole] derivatives exhibit important biological activities. An enantioselective organocatalytic approach to the rapid synthesis of spiro[pyrrolidin-3,3'-oxindole] derivatives with high enantiopurity and structural diversity is described. The asymmetric catalytic three-component 1,3-dipolar cycloaddition of a broad range of methyleneindolinones with aldehy...

Journal: :Journal of the American Chemical Society 2012
Changwu Zheng Dian Wang Shannon S Stahl

Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugated dienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (nonoxidative) Heck reaction between a vinyl b...

2016
Bo Wang Di Qiu Yan Zhang Jianbo Wang

The recent development of intermolecular C-H insertion in the application of C(sp(3))-H bond functionalizations, especially for light alkanes, is reviewed. The challenging problem of regioselectivity in C-H bond insertions has been tackled by the use of sterically bulky metal catalysts, such as metal porphyrins and silver(I) complexes. In some cases, high regioselectivity and enantioselectivity...

Journal: :Journal of the American Chemical Society 2012
Takaki Imaizumi Yasuhiro Yamashita Shū Kobayashi

We developed a 1,3-dipolar cycloaddition reaction of azomethine imines with terminal alkynes catalyzed by group 11 metal amides to provide N,N-bicyclic pyrazolidinone derivatives. This reaction afforded the cycloadducts in a unique 5,7-disubstituted manner. Furthermore, we succeeded in applying this catalysis to asymmetric reactions, and the desired heterocycles were produced in high yields wit...

Journal: :Molecules 2017
Cédric Spitz Alain G Giuglio-Tonolo Thierry Terme Patrice Vanelle

A mild and metal-free regiodivergent addition of carbon nucleophiles to α,β-unsaturated electrophiles was developed. Total 1,2-regioselectivity was observed in the addition of nitrobenzyl chloride derivative 1 to α,β-unsaturated aldehydes 2 in the presence of TDAE. Moreover, the reaction between p-nitrobenzyl chloride 1a and α,β-unsaturated iminium salts 4 led to the formation of the 1,4-adduct...

2014
Rongling Yang Xueming Liu Zhiyi Chen Chunying Yang Yaosheng Lin Siyuan Wang Claudio M. Soares

Highly efficient and regioselective acylation of pharmacologically interesting gastrodin with vinyl undecylenic acid has been firstly performed through an enzymatic approach. The highest catalytic activity and regioselectivity towards the acylation of 7'-hydroxyl of gastrodin was obtained with Pseudomonas cepacia lipase. In addition, it was observed the lipase displayed higher activity in the e...

2014
Todd K. Hyster Christopher C. Farwell Andrew R. Buller John A. McIntosh Frances H. Arnold

We recently demonstrated that variants of cytochrome P450BM3 (CYP102A1) catalyze the insertion of nitrogen species into benzylic C-H bonds to form new C-N bonds. An outstanding challenge in the field of C-H amination is catalyst-controlled regioselectivity. Here, we report two engineered variants of P450BM3 that provide divergent regioselectivity for C-H amination-one favoring amination of benz...

Journal: :Journal of Molecular Structure 2021

The tosyl functional group is commonly used in carbohydrate chemistry as a nucleofuge. Tosylation of the primary hydroxyls carbohydrates are generally performed after orthogonal protection/deprotection reactions. However, it can be done regioselectively from unprotected sugars. Several examples have been described literature starting free monosaccharides. Yields good but may vary according to n...

Journal: :Journal of chemical information and modeling 2011
Jed Zaretzki Charles Bergeron Patrik Rydberg Tao-wei Huang Kristin P. Bennett Curt M. Breneman

This article describes RegioSelectivity-Predictor (RS-Predictor), a new in silico method for generating predictive models of P450-mediated metabolism for drug-like compounds. Within this method, potential sites of metabolism (SOMs) are represented as "metabolophores": A concept that describes the hierarchical combination of topological and quantum chemical descriptors needed to represent the re...

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