1140972-11-7Relevant academic research and scientific papers
Cooperative Catalysis with Coupled Chiral Induction in 1,3-Dipolar Cycloadditions of Azomethine Ylides
Cayuelas, Alberto,Larra?aga, Olatz,Selva, Verónica,Nájera, Carmen,Akiyama, Takahiko,Sansano, José M.,de Cózar, Abel,Miranda, José I.,Cossío, Fernando P.
supporting information, p. 8092 - 8097 (2018/05/30)
1,3-Dipolar cycloadditions (1,3-DC) between imino esters (as precursors of N-metallated azomethine ylides) and π-deficient alkenes are promoted by cooperative asymmetric Lewis acid/Br?nsted base catalysis. The components of these catalytic pairs are silver salts derived from enantiopure commercially available BINOL-based phosphoric acids and Cinchona alkaloids. Chiral phosphoric silver(I) salts promote HOMO raising of in situ formed 1,3-dipoles, whereas protonated cinchona alkaloids generate a LUMO lowering for the dipolarophiles resulting in a global acceleration of the 1,3-DC. The best results were obtained with BINOL-derived silver phosphate and hydrocinchonine. Matching between both cooperative metallo- and organocatalyst results in an enhanced enantiomeric excess, superior to that reached by both separate components. NOESY experiments and DFT calculations are compatible with a non-covalent interaction (hydrogen bond) between both catalysts, which results in close contacts and mutually coupled chiral environments.
Binap-silver salts as chiral catalysts for the enantioselective 1,3-dipolar cycloaddition of azomethine ylides and alkenes
Mancebo-Aracil, Juan,Martin-Rodriguez, Maria,Najera, Carmen,Sansano, Jose M.,Costa, Paulo R.R.,De Lima, Evanoel Crizanto,Dias, Ayres G.
, p. 1596 - 1606 (2013/02/23)
Binap-AgSbF6 catalyzed 1,3-dipolar cycloadditions between azomethine ylides and electrophilic alkenes are described and compared with analogous transformations mediated by other Binap-silver(I) salt complexes. Maleimides and 1,2-bis(phenylsulfo
Enantioselective synthesis of polysubstituted prolines by Binap-silver-catalyzed 1,3-dipolar cycloadditions
Najera, Carmen,de Gracia Retamosa,Sansano, Jose M.,Cozar, Abel de,Cossio, Fernando P.
experimental part, p. 2913 - 2923 (2009/07/11)
The enantioselective 1,3-dipolar cycloaddition reaction of stabilized azomethine ylides, generated from iminoesters, with maleimides was efficiently achieved by intermediacy of an equimolar mixture of chiral (R)- or (S)-Binap and AgClO4. The high stability of the titled catalytic metal-complex to light exposure and its insolubility in toluene made possible its recovery and reutilization in other new process. In order to get a better understanding of the behavior of these chiral catalysts, we have carried out DFT1 calculations demonstrating the experimentally observed high enantio- and endo-selectivity through a very asynchronous transition state.
