first highly enantioselective and regiodivergent conjugate addition of trialkylaluminium reagents to nitrodienes and nitroenynes is described. By a design of the substrate and a fine-tuning of the reaction conditions, it is possible to selectively form the 1,4- or 1,6-adduct. The same combination of catalyst, copper source, and a ferrocene-based phosphine ligand afforded enantioselectivities up to 95%
Probing α‐Amino Aldehydes as Weakly Acidic Pronucleophiles: Direct Access to Quaternary α‐Amino Aldehydes by an Enantioselective Michael Addition Catalyzed by Brønsted Bases
The high tendency of α‐amino aldehydes to undergo 1,2‐additions and their relatively low stability under basic conditions have largely prevented their use as pronucleophiles in the realm of asymmetric catalysis, particularly for the production of quaternary α‐amino aldehydes. Herein, it is demonstrated that the chemistry of α‐amino aldehydes may be expanded beyond these limits by documenting the first
<i>syn</i>
‐Selective Michael Reaction of α‐Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Brønsted Bases
作者:Ane García‐Urricelqui、Abel Cózar、Teresa E. Campano、Antonia Mielgo、Claudio Palomo
DOI:10.1002/ejoc.202100355
日期:2021.7.7
α-Branched aryl acetaldehydes are efficiently activated by a cinchona based squaric acid-derived peptide to provide, upon reaction with nitroolefins, 2,2,3-trisubstituted syn γ-nitroaldehydes with high diastereo- and enantioselectivity.
Self‐assembled catalyst: A new kind of chiral supramolecular organocatalyst, self‐assembled from chiral amines and poly(alkene glycol)s, was developed. The resulting self‐assemblies were found to be highlyefficient in the asymmetriccatalysis of the unusual Diels–Alder reaction between cyclohexenones and nitrodienes, nitroenynes or nitroolefins, giving excellent chemo‐, regio‐ and enantioselectivities
Cerium(<scp>iii</scp>)-catalyzed cascade cyclization: an efficient approach to functionalized pyrrolo[1,2-a]quinolines
作者:Chengtao Feng、Yizhe Yan、Zhenglei Zhang、Kun Xu、Zhiyong Wang
DOI:10.1039/c4ob00708e
日期:——
A general and practical route to the synthesis of multisubstituted pyrrolo[1,2-a]quinolines has been described from 2-alkylazaarenes and nitroolefins using cerium chloride as a catalyst via a tandem Michael addition, cyclization and aromatization.