Development of Non-<i>C</i>2-symmetric ProPhenol Ligands. The Asymmetric Vinylation of <i>N</i>-Boc Imines
作者:Barry M. Trost、Chao-I (Joey) Hung、Dennis C. Koester、Yan Miller
DOI:10.1021/acs.orglett.5b01755
日期:2015.8.7
The development and application of a newgeneration of non-C2-symmetric ProPhenol ligands is reported herein. Rational design of the ProPhenol ligand paved the way to the first catalytic and asymmetric vinylation of N-Boc imines via hydrozirconation giving rise to valuable allylic amines in excellent yields and enantioselectivities. The utility of this method was demonstrated by developing the shortest
Diastereoselective preparation of novel tetrahydrooxazinones via heterocycloaddition of N-Boc, O-Me-acetals
作者:Patricia Gizecki、Ramzi Ait Youcef、Céline Poulard、Robert Dhal、Gilles Dujardin
DOI:10.1016/j.tetlet.2004.10.154
日期:2004.12
Under Lewis acid conditions, reaction of N-Boc, O-Me acetals with the (R)-(+)-O-vinyl-pantolactone does not lead to the expected dihydrooxazine, but to the corresponding tetrahydrooxazinone, as a result of the loss of the t-Bu group. A diastereoselective and asymmetrical way to these new heterocyclic compounds is described, together with the first evidence of their ability to undergo N-acylation.
Asymmetric phase-transfer catalysis was first applied to the synthesis of chiral N,S-acetals by using amino acid-based bifunctional thiourea-ammonium salt catalysts. The reaction could be performed on the gram scale to give up to 93% ee and 99% yield with a catalyst loading as low as 0.1 mol % within 5 min.
Highly Enantioselective Titanium-Catalyzed Cyanation of Imines at Room Temperature
作者:Abdul Majeed Seayad、Balamurugan Ramalingam、Kazuhiko Yoshinaga、Takushi Nagata、Christina L. L. Chai
DOI:10.1021/ol902540h
日期:2010.1.15
A highly active and enantioselective titanium-catalyzed cyanation of imines at roomtemperature is described. The catalyst used is a partially hydrolyzed titanium alkoxide (PHTA) precatalyst together with a readily available N-salicyl-β-aminoalcohol ligand. Up to 98% ee was obtained with quantitative yields in 15 min of reaction time using 5 mol % of the catalyst. Various N-protecting groups such as
Asymmetric Synthesis of <i>anti</i>-β-Amino-α-Hydroxy Esters via Dynamic Kinetic Resolution of β-Amino-α-Keto Esters
作者:C. Guy Goodman、Dung T. Do、Jeffrey S. Johnson
DOI:10.1021/ol4009206
日期:2013.5.17
method for the asymmetricsynthesis of enantioenriched anti-α-hydroxy-β-amino acid derivatives by enantioconvergent reduction of the corresponding racemic α-keto esters is presented. The requisite α-keto esters are prepared via Mannich addition of ethyl diazoacetate to imines followed by oxidation of the diazo group with Oxone. Implementation of a recently developed dynamickinetic resolution of β-substituted-α-keto