Development of a Phase-Transfer-Catalyzed, [2,3]-Wittig Rearrangement
摘要:
An investigation into the use of phase-transfer catalysis for the [2,3]-sigmatropic rearrangement of allyloxy carbonyl compounds is described. Initial studies focused on identifying viable substrate classes that would undergo selective [2,3]-rearrangement under phase-transfer catalysis. Under certain conditions, the [2,3]-sigmatropic rearrangement of allyloxy carbonyl compounds takes place in the presence of a phase-transfer agent, providing a rare example of a phase-transfer-catalyzed unimolecular reaction. In the course of this investigation, it was found that catalysis is dependent on several variables including base concentration, catalyst structure, and substrate lipophilicity. Preliminary testing of chiral, nonracemic phase-transfer catalysts has shown promising levels of enantioselectivity for future development.
Enantioselective Spirocyclopropanation of <i>para</i>-Quinone Methides Using Ammonium Ylides
作者:Lukas Roiser、Mario Waser
DOI:10.1021/acs.orglett.7b00869
日期:2017.5.5
The use of Cinchonaalkaloid-based chiral ammonium ylides allows for the first highlyenantioselective and broadly applicable spirocyclopropanation reactions of para-quinone methides. This strategy provides a straightforward protocol toward the chiral spiro[2.5]octa-4,7-dien-6-one skeleton, which is a frequently found structural motif in important biologically active molecules.
The First and Second <i>Cinchona</i> Rearrangement. Two Fundamental Transformations of Alkaloid Chemistry
作者:M. Heiko Franz、Stefanie Röper、Rudolf Wartchow、H. M. R. Hoffmann
DOI:10.1021/jo030363s
日期:2004.4.1
Stereochemistry, products, and driving forces of the “first and second Cinchona rearrangement” have been investigated and a unified theory is presented. The first cage expansion affords [3.2.2]azabicyclic α-amino ether and is formulated via a configurationally stable bridgehead iminium ion and quasiequatorial nucleophilic attack. The second cage expansion affords β-functionalized [3.2.2]azabicycles
The mechanism of enantiodifferentiation in the hydrogenation of alkenoic acidsover cinchona-modified Pd has been investigated using the tiglic acid → 2-methyl-butanoic acid transformation as test reaction. Application of simple derivatives of cinchonidine, modified at the (C-9)–OH and/or the quinuclidine nitrogen, proved that both functional groups are involved in the enantiodiscriminating step. Addition
The reaction of cinchonidine (cinchonine)-derived ammonium salts with nitroolefins in the presence of Cs2CO3 to afford optically active isoxazolineN-oxides with excellent ee and high de values has been developed.
[EN] PROCESS FOR PREPARING DIASTEREOMERICALLY ENRICHED PHOSPHORAMIDATE DERIVATIVES OF NUCLEOSIDE COMPOUNDS FOR TREATMENT OF VIRAL INFECTIONS<br/>[FR] PROCÉDÉ DE PRÉPARATION DE DÉRIVÉS DE PHOSPHORAMIDATES ENRICHIS EN DIASTÉRÉO-ISOMÈRES DE COMPOSÉS DE NUCLÉOSIDES, DESTINÉS AU TRAITEMENT D'INFECTIONS VIRALES
申请人:BRISTOL MYERS SQUIBB CO
公开号:WO2014008236A1
公开(公告)日:2014-01-09
The present invention is directed to a process for preparing diastereomerically enriched nucleoside phosphoramidates having the formula I: