scholarly journals The Silicon–Hydrogen Exchange Reaction: Catalytic Kinetic Resolution of 2-Substituted Cyclic Ketones

Synlett ◽  
2021 ◽  
Author(s):  
Benjamin List ◽  
Hui Zhou ◽  
Pinglu Zhang

We have recently reported the strong and confined, chiral acid-catalyzed asymmetric “silicon−hydrogen exchange reaction”. One aspect of this transformation is that it enables access to enantiopure enol silanes in a tautomerizing σ-bond metathesis, via deprotosilylation of ketones with allyl silanes as the silicon source. However, until today, this reaction has not been applied to racemic, 2-substituted, cyclic ketones. We show here that these important substrates readily undergo a highly enantioselective kinetic resolution furnishing the corresponding kinetically preferred enol silanes. Mechanistic studies suggest the fascinating possibility of advancing the process to a dynamic kinetic resolution.

1979 ◽  
Vol 57 (22) ◽  
pp. 2896-2901 ◽  
Author(s):  
Robert A. McClelland ◽  
William F. Reynolds

Rate constants have been obtained for the acid-catalyzed N–H exchange of N-methyl, 2,N-dimethyl, and 2,4,6,N-tetramethylbenzamide and the acid-catalyzed isomerization of the three corresponding N,N-dimethylbenzamides. The ratio [Formula: see text] increases significantly with increased number of ortho methyl substituents. This is explained in terms of a suggestion of Perrin, that C—N bond rotation is not completely free in the N-protonated amide, since it must compete with a diffusion limited deprotonation reaction. The isomerization reaction, which requires such a rotation, is therefore slowed by ortho methyl substituents which hinder rotation, relative to the exchange reaction, which does not require rotation.


Author(s):  
Xue-Jiao Lv ◽  
Yong-Chao Ming ◽  
Hui-Chun Wu ◽  
Yankai Liu

A Brønsted acid-catalyzed cascade acyclic N,O-hemiaminal formation/oxa-Michael reaction is developed for the synthesis of cis-2,6-disubstituted tetrahydropyrans bearing an exo amide group, that is, cyclic N,O-aminals. By using TsOH, various different...


2020 ◽  
Vol 56 (43) ◽  
pp. 5815-5818 ◽  
Author(s):  
Xiang Li ◽  
Zi-Biao Zhao ◽  
Mu-Wang Chen ◽  
Bo Wu ◽  
Han Wang ◽  
...  

The first efficient palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones has been described through dynamic kinetic resolution under acidic conditions, providing a facile access to chiral trans cycloalkanols.


2021 ◽  
Author(s):  
Fuzhuo Li ◽  
Li-Cheng Yang ◽  
Jingyang Zhang ◽  
Jason Chen ◽  
Hans Renata

We report a biocatalytic transamination method to prepare a broad range of b-branched a-amino acids that proceeds with high diastereo- and enantioselectivity. Mechanistic studies show that the transformation proceeds through a dynamic kinetic resolution process that is unique to the optimal enzyme. To highlight its utility and practicality, the biocatalytic reaction is applied to the synthesis of several cyclic fragments and in the first total synthesis of jomthonic acid A.


2021 ◽  
Vol 86 (18) ◽  
pp. 13169-13174
Author(s):  
Pedro P. De Castro ◽  
Gabriel M. F. Batista ◽  
Giovanni W. Amarante ◽  
Hélio F. Dos Santos

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