نتایج جستجو برای: unsaturated β

تعداد نتایج: 192068  

Journal: :Organic letters 2012
Kun Jiang Bhoopendra Tiwari Yonggui Robin Chi

A diastereoselective access to β-lactam fused spirocyclic oxindoles and related compounds bearing all carbon spiro centers is described. This N-heterocyclic carbene-catalyzed process employed challenging β,β-disubstituted α,β-unsaturated imines to react with enals.

Journal: :Chemical science 2017
Jinchao Yang Alistair J M Farley Darren J Dixon

The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated β-substituted-α,β-unsaturated esters catalyzed by a bifunctional iminophosphorane (BIMP) organocatalyst is described. The low acidity of the alkyl thiol pro-nucleophiles is overcome by the high Brønsted basicity of the catalyst and the chiral scaffold/thiourea hydrogen-bond donor moiety provides the required enant...

Journal: :Organic & biomolecular chemistry 2012
Shveta Pandiancherri Sarah J Ryan David W Lupton

Lewis base catalysed 1,3-dipolar cycloaddition between α,β-unsaturated acyl fluorides and N-[(trimethylsilyl)methyl]amino ethers has been achieved using 1 mol% DMAP. Competition experiments and (19)F-NMR studies indicate that the cycloaddition occurs preferentially between the α,β-unsaturated acyl fluoride and the unstabilised azomethine ylide. In addition, an enantioselective variant, using ch...

Journal: :Organic letters 2011
Jun-ichi Matsuo Kosuke Harada Mizuki Kawano Ryosuke Okuno Hiroyuki Ishibashi

3-[(Trialkylsilyl)methyl]cyclobutanones reacted with aldehydes by activation with titanium(IV) chloride to give acyclic β,γ-unsaturated β'-hydroxyketones.

Journal: :Organic & biomolecular chemistry 2015
Brij Bhushan Ahuja Arumugam Sudalai

An efficient catalytic route for the synthesis of α,β-unsaturated nitriles from easily accessible gem-dibromoolefins has been developed. The method utilized inexpensive reagents such as Cu2O as a catalyst, L-proline as a ligand and NaCN as a cyanide source to afford α,β-unsaturated nitriles in high yields (62-86%). A deuterium exchange study has shown that one of the bromide atoms of gem-dibrom...

Journal: :Chemical record 2017
Mingsheng Xie Lili Lin Xiaoming Feng

In this review, the recent developments in catalytic asymmetric inverse-electron-demand hetero-Diels-Alder reaction, which is recognized as one of the most powerful routes to construct highly functionalized and enantioenriched six-membered heterocycles, are described. The article is organized on the basis of different kinds of electron-deficient heterodienes, including α,β-unsaturated ketones/a...

2018
Dimitris Kalaitzakis Manolis Sofiadis Myron Triantafyllakis Konstantinos Daskalakis Georgios Vassilikogiannakis

Asymmetric and site-selective formal [3 + 2]-annulations of γ-alkyl-β,γ-unsaturated γ-lactams with α,β-unsaturated aldehydes have been developed. These organocatalysed transformations yield high value enantioenriched bicyclic γ-lactams with up to four new stereocenters (sometimes including a quarternary carbon). The overall transformation starts from simple and readily accessible furans and ove...

2014
Jamie M. Neely Tomislav Rovis

α,β-Unsaturated carboxylic acids undergo Rh(III)-catalyzed decarboxylative coupling with α,β-unsaturated O-pivaloyl oximes to provide substituted pyridines in good yield. The carboxylic acid, which is removed by decarboxylation, serves as a traceless activating group, giving 5-substituted pyridines with very high levels of regioselectivity. Mechanistic studies rule out a picolinic acid intermed...

Journal: :Organic letters 2014
Smita Basu Vaishali Gupta Johannes Nickel Christoph Schneider

The enantioselective vinylogous Michael reaction of vinylketene silyl N,O-acetals derived from α,β-unsaturated N-acyl pyrroles and a broad range of α,β-unsaturated aldehydes proceeds with good regio-, diastereo-, and enantioselectivity when the Hayashi-Jørgensen diphenylprolinolsilylether was employed as a chiral organocatalyst. Products were obtained in generally good yields and as single ster...

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