A new class of amine N-oxides derived from trans-2,5-diphenylpyrrolidine were synthesized in enantiomerically pure form and tested as metal-free catalysts in the reaction of aldehydes with allyl(trichloro)silane to afford homoallylic alcohols. The products were obtained in fair to good yields and up to 85% ee. The behavior of structurally different catalysts and the influence of a coordinating unit present in the organocatalyst on controlling the stereochemical efficiency of the reaction were also investigated. Noteworthy a catalyst capable of promoting the allylation of aliphatic aldehydes with an almost unprecedent and unusually high enantioselectivity, up to 85%, was identified.
A general, enantioselective synthesis of 2-substituted thiomorpholines and thiomorpholine 1,1-dioxides
作者:Carson W. Reed、Craig W. Lindsley
DOI:10.1016/j.tetlet.2019.151104
日期:2019.10
In the course of our drug discovery programs, we had need to access chiral, 2-substituted thiomorpholines and their oxidized congeners, thiomorpholine 1,1-dioxides. Here, we disclose a high-yielding, general protocol for the enantioselective synthesis of C2-functionalized thiomorpholines and thiomorpholine 1,1-dioxides.
Pseudo-C2-symmetric chiral phosphorus ylide is designed and synthesized for the enantioselective preparation of allenic esters, amides, ketone, and nitrile. Up to 92% ee is achieved.
Design and synthesis of new bis-hydrazones and pyridine bis-hydrazones: application in the asymmetric Diels-Alder reaction
作者:David Monge、Antonio Bermejo、Juan Vázquez、Rosario Fernández、José M. Lassaletta
DOI:10.3998/ark.5550190.0014.205
日期:——
The design of two different types of new chiral bis -hydrazones 5 (bidentate N,N ligands, type A ) and pyridinebis-hydrazones 7 ('pincer' N,N,N ligands, type B) is discussed. Preliminary results on the copper(II)-catalyzed Diels-Alderreaction of N-(E)-crotyloxazolidin-2-one ( 8) with cyclopentadiene ( 9) revealed that the (2 S,6 S)-2,6-diphenylpiperidine C2-symmetric substructure in pyridine bis-hydrazone
Development of Chiral Bis-hydrazone Ligands for the Enantioselective Cross-Coupling Reactions of Aryldimethylsilanolates
作者:Scott E. Denmark、Wen-Tau T. Chang、K. N. Houk、Peng Liu
DOI:10.1021/jo502388r
日期:2015.1.2
aryldimethylsilanolates and arylbromides result in biaryl products with the same configuration and similar enantioselectivities implying that reductive elimination is the stereodetermining step. The origin of stereoselectivity is rationalized through computational modeling of diarylpalldium(II) complex which occurs through a conrotatory motion for the two aryl groups undergoing C–C bondformation.