Synthesis of <i>trans</i>-3-Substituted Cyclohexylamines via Brønsted Acid Catalyzed and Substrate-Mediated Triple Organocatalytic Cascade Reaction
作者:Benjamin List、Jian Zhou
DOI:10.1055/s-2007-984877
日期:——
We report a new organocatalytic cascade reaction. A combination of the amine substrate with a catalytic amount of a Brønsted acid merges enamine and iminium catalysis with Brønsted acid catalysis in a new organocatalytic cascade reaction. We found that the aniline substrate itself in combination with a catalytic amount of PTSA·H2O can function as an aminocatalyst accomplishing an aldol condensation-conjugate reduction cascade, which terminates in a Brønsted acid catalyzed reductive amination incorporating the amine substrate into the final product. This transformation furnishes trans-3-substituted cyclohexyl amines in good yields and good diastereoselectivities.
Phosphine Oxide-Catalyzed Enantioselective Intramolecular Aldol Reaction via Regioselective Enolization of Unsymmetrical Diketones with Tetrachlorosilane
The phosphine oxide-catalyzed asymmetric intramolecular aldol reactions of diketones were investigated. The combination of tetrachlorosilane and a chiral phosphine oxide catalyst promoted the acetyl-selective enolization of diketones, and the subsequent intramolecular aldol reaction occurred in an enantioselective manner. The introduction of two trimethylsilyl groups at the 4- and 4′-positions in BINAP
Cyclopentane Formation from Flexible Precursors Using Samarium(II) Reagents
作者:Christopher D. Aretz、Humberto Escobedo、Bryan J. Cowen
DOI:10.1002/ejoc.201800102
日期:2018.4.30
This study presents three efficient methods for five‐membered ring carbocycle synthesis using samarium(II) reagents. Simple organic starting materials engage in intramolecular Reformatsky aldol, enolate alkylation, and pinacol cyclizations. A promising lead result has also been established demonstrating enantioselectivity in a chiral ligand controlled Reformatsky aldol reaction.