An Aminocatalyzed Stereoselective Strategy for the Formal α-Propargylation of Ketones
作者:Igor D. Jurberg
DOI:10.1002/chem.201701433
日期:2017.7.21
A two‐step reaction sequence is described for the asymmetric formal α‐propargylation of ketones. This approach takes advantage of an aminocatalyzed conjugateaddition of ketones to alkylidene isoxazol‐5‐ones, followed by a controlled nitrosative degradation event. The target compounds can be accessed in broad scope, in moderate to good yields, perfect diastereocontrol and good to excellent enantioselectivity
The regioselective synthesis of N-unsubstituted pyrrol-3-yl hydroxamates starting from (Z)-4-arylmethyleneisoxazol-5-ones may be readily achieved by the use of sequential 5(4H)-oxazolone cycloaddition and nitrile oxide addition reactions.
Cooperative Catalysis with Coupled Chiral Induction in 1,3-Dipolar Cycloadditions of Azomethine Ylides
作者:Alberto Cayuelas、Olatz Larrañaga、Verónica Selva、Carmen Nájera、Takahiko Akiyama、José M. Sansano、Abel de Cózar、José I. Miranda、Fernando P. Cossío
DOI:10.1002/chem.201801433
日期:2018.6.7
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/Brønsted base catalysis. The components of these catalytic pairs are silver saltsderivedfrom enantiopure commercially available BINOL‐based phosphoric acids and Cinchona alkaloids. Chiral phosphoric silver(I) salts promote
2-arylbenzimidazolines (8), generated in situ from o-phenylenediamine (7) and the appropriate arylaldehydes, by reaction with 4-arylmethylenepyrazol-5-ones (1) or isoxazol-5-ones (2) produce the 4-arylmethylderivatives (3) or (4) and the C,C- (5) or the C,N-linkeddimers. The reaction was rationalised on the basis of the role of 2-arylbenzimidazoline as a reducing agent and proceeds by a non-chain
Enantioselective Synthesis of Functionalized Diazaspirocycles from 4‐Benzylideneisoxazol‐5(4<i>H</i>)‐one Derivatives and Isocyanoacetate Esters
作者:Pablo Martínez‐Pardo、Adrián Laviós、Amparo Sanz‐Marco、Carlos Vila、José R. Pedro、Gonzalo Blay
DOI:10.1002/adsc.202000611
日期:2020.9.8
spirocyclic compounds bearing three contiguous stereocenters and high functionalization were obtained through a formal [3+2] cycloaddition reaction catalyzed by a cooperative system. The spiro compounds were synthesized from 4‐arylideneisoxazol‐5‐ones and isocyanoacetate esters using a bifunctional squaramide/Brønsted base organocatalyst derived from a Cinchona alkaloid and silver oxide as Lewis acid. This method