Stereoselective Hydrosilylation of Enals and Enones Catalysed by Palladium Nanoparticles
作者:Meryem Benohoud、Sakari Tuokko、Petri M. Pihko
DOI:10.1002/chem.201100655
日期:2011.7.18
A highly versatile and efficient hydrosilylation method by palladium nanoparticle catalysis allows the direct and chemoselective synthesis of 1) enolsilanes of high isomeric purity, 2) saturated aldehydes or ketones, or 3) the corresponding saturated acetals from α,β‐unsaturated aldehydes or ketones. The choice of the product is determined by simply switching the solvent from THF to mixtures of THF/water
Ketone Synthesis by a Nickel-Catalyzed Dehydrogenative Cross-Coupling of Primary Alcohols
作者:Thomas Verheyen、Lars van Turnhout、Jaya Kishore Vandavasi、Eric S. Isbrandt、Wim M. De Borggraeve、Stephen G. Newman
DOI:10.1021/jacs.9b03280
日期:2019.5.1
intermolecular coupling of primaryalcohols and organotriflates has been developed to provide ketones by the action of a Ni(0) catalyst. This oxidative transformation is proposed to occur by the union of three distinct catalytic cycles. Two competitive oxidation processes generate aldehyde in situ via hydrogentransfer oxidation or (pseudo)dehalogenation pathways. As aldehyde forms, a Ni-catalyzed carbonyl-Heck
Lanthanoid triisopropoxides are active catalysts for aldol reactions. Aldehydes give the corresponding β-hydroxyaldehydes at low temperatures in good yields, whereas ketones are less reactive, but form condensation products at high temperatures. Exceptionally, γ- or δ-diketones easily undergo condensation to give five- and six-membered unsaturated ketones in high yields. The lanthanoid propoxides, catalyzing the Michael addition of ketones to α,β-unsaturated ketones, which give δ-diketones, are also good catalysts for the Robinson-type annelation. In these reactions, the catalytic activity of the lanthanum propoxide is higher than those of the heavy lanthanoid propoxides, and is almost comparable to that of sodium isopropoxide. Since aluminum triisopropoxide shows poor activity, the lanthanoid propoxides are considerably basic for trivalent metal alkoxides.
Cooperative Organocatalysis for the Asymmetric γ Alkylation of α-Branched Enals
作者:Giulia Bergonzini、Silvia Vera、Paolo Melchiorre
DOI:10.1002/anie.201004761
日期:2010.12.10
α Branched leads to γ: The direct and enantioselective γalkylation of α‐substituted α,β‐unsaturated aldehydes under dienamine catalysis has been achieved. A cooperative catalysis system that involves dienamine activation of α‐branched enals and chiral Brønsted acid catalysis promotes an SN1‐alkylation pathway while ensuring complete γ‐site selectivity and high stereocontrol (see scheme; Bn=benzyl)
α分支导致γ:在二烯胺催化下,实现了α-取代的α,β-不饱和醛的直接和对映选择性γ烷基化。一个合作的催化系统涉及α-支链烯类的二烯胺活化和手性布朗斯台德酸催化,可促进S N 1烷基化途径,同时确保完全的γ位选择性和高度立体控制(参见方案; Bn =苄基)。
A comprehensive investigation and optimisation on the proteinogenic amino acid catalysed homo aldol condensation
作者:Karoline A. Ostrowski、Dominik Lichte、Moritz Stuck、Andreas J. Vorholt
DOI:10.1016/j.tet.2015.11.069
日期:2016.2
A systematic investigation regarding the application of catalytic amounts of all 20 proteinogenic amino acids in the homo aldolcondensation of aldehydes is described obtaining excellent yields of the desired α,β-unsaturated aldehyde. These investigations proved the basic amino acids, lysine and arginine, are effective as organocatalysts, if comparably low concentrations are applied. Through the stepwise