scholarly journals Vanadium-catalyzed selenide oxidation with in situ [2,3] sigmatropic rearrangement (SOS reaction): scope and asymmetric applications

2004 ◽  
Vol 2 (9) ◽  
pp. 1315-1329 ◽  
Author(s):  
T. Campbell Bourland ◽  
Rich G. Carter ◽  
Alexandre F. T. Yokochi
Keyword(s):  
Sigmatropic Rearrangement

Acylation of Nitronates: [3,3]-Sigmatropic Rearrangement of in Situ Generated N-Acyloxy,N-oxyenamines

2018 ◽  
Vol 83 (18) ◽  
pp. 11057-11066 ◽  
Author(s):  
Aleksandr O. Kokuev ◽  
Yulia A. Antonova ◽  
Valentin S. Dorokhov ◽  
Ivan S. Golovanov ◽  
Yulia V. Nelyubina ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement

In situ preparation of cyclopropanones with the bicyclo[3.1.0]hexan-6-one skeleton (substituted examples of the Loftfield intermediate). Confirmation of a very facile intramolecular alkyl cyclopropanone – dienol rearrangement

1996 ◽  
Vol 74 (1) ◽  
pp. 79-87 ◽  
Author(s):  
T. S. Sorensen ◽  
F. Sun
Keyword(s):  
Nmr Spectroscopy ◽  
Sigmatropic Rearrangement ◽  
Unsaturated Ketone ◽  
Tert Butyl ◽  
H Nmr ◽  
In Situ Preparation ◽  
Rate Determining Step ◽  
Enol Formation ◽  
C Nmr

Four substituted bicyclo[3.1.0]hexan-6-ones (cyclopropanones) were prepared in situ, starting from the corresponding 2,6-dibromocyclohexanone and reductively removing the bromine atoms with the organometallic salt PPN+Cr(CO)4NO− The reaction is essentially instantaneous at −78 or−100 °C, and can be conveniently carried out in an NMR tube for easy characterization of the products by low-temperature 1H and 13C NMR spectroscopy. The1,5-di-tert-butyl and 1-tert-butyl analogs were thermally stable to ca. 0 °C, but the 1-tert-butyl-5-methyl and 1-tert-butyl-5-ethyl derivatives were extremely labile, rearranging at ca. −80 °C into a cross-conjugated enol, where the methyl (or ethyl) substituent was converted into an exomethylene group. These enols were also characterized as in situ species using 1H and 13C NMR spectroscopy, and by allowing the enol → α,β-unsaturated ketone rearrangement to take place at about 25 °C. The mechanism of the enol formation was investigated using a 1 -tert-butyl-5-CD3 analog, and the kH/kD ratio for enol formation was determined to be 6 ± 2. From this, the rate-determining step in the enol formation was postulated as a C-H → H-O transfer of a hydrogen atom in a cyclohexyl oxyallyl intermediate. The 1,5-di-tert-butylbicyclohexanone shows dynamic 1H NMR line broadening, the origin of which is also proposed to involve a cyclohexyl oxyallyl intermediate. Key words: cyclopropanone, oxyallyl, bicyclo[3.1.0]hexan-6-one, dienol, sigmatropic rearrangement.

scholarly journals Exploring the Scope of Tandem Palladium and Isothiourea Relay Catalysis for the Synthesis of α-Amino Acid Derivatives

Molecules ◽  
2020 ◽  
Vol 25 (10) ◽  
pp. 2463
Author(s):  
Jacqueline Bitai ◽  
Alexandra M. Z. Slawin ◽  
David B. Cordes ◽  
Andrew D. Smith
Keyword(s):  
Amino Acid ◽  
Transition State ◽  
Quaternary Ammonium ◽  
Palladium Catalyst ◽  
Quaternary Ammonium Salts ◽  
Sigmatropic Rearrangement ◽  
Ammonium Salts ◽  
Amino Acid Derivatives ◽  
Substitution Pattern

The scope and limitations of a tandem N-allylation/[2,3]-rearrangement protocol are investigated through the incorporation of a variety of functional groups within an allylic phosphate precursor. This method uses readily accessible N,N-dimethylglycine aryl esters and functionalized allylic phosphates, forming quaternary ammonium salts in situ in the presence of a palladium catalyst. Subsequent enantioselective [2,3]-sigmatropic rearrangement, promoted by the chiral isothiourea tetramisole, generates α-amino acid derivatives with two contiguous stereocenters. The incorporation of electron-withdrawing ester and amide groups gave the best results, furnishing the desired products in moderate to good yields (29–70%), with low diastereocontrol (typically 60:40 dr) but high enantioselectivity (up to 90:10 er). These results indicate that substrate–catalyst interactions in the proposed transition state are sensitive to the substitution pattern of the substrates.

Aryne-mediated [2,3]-sigmatropic rearrangement of tertiary 2,3-allenylamines bearing an electron-withdrawing group at the α-position

2021 ◽  
Author(s):  
Lu Han ◽  
Xue-Ting Zhang ◽  
Dong Xie ◽  
Shi-Kai Tian
Keyword(s):  
Sigmatropic Rearrangement ◽  
Rearrangement Reaction ◽  
Electron Withdrawing Group

An unprecedented [2,3]-sigmatropic rearrangement reaction of quaternary 2,3-allenylammonium ylides, generated in situ from tertiary 2,3-allenylamines and arynes, has been established. With 2-(trimethylsilyl)aryl triflates as aryne precursors, a range of tertiary...

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