A Simple Primary Amine Catalyst for Enantioselective α-Hydroxylations and α-Fluorinations of Branched Aldehydes
摘要:
A new primary amine catalyst for the asymmetric a-hydroxylation and a-fluorination of alpha-branched aldehydes is described. The products of the title transformations are generated in excellent yields with high enantioselectivities. Both processes can be performed within short reaction times and on gram scale. The similarity in results obtained in both reactions, combined with computational evidence, implies a common basis for stereoinduction and the possibility of a general catalytic mechanism for a-functionalizations. Promising initial results in alpha-amination and alpha-chlorination reactions support this hypothesis.
The isomerization of epoxides to aldehydes using the readily available Crabtree's reagent is described. The aldehydes were transformed into synthetically useful amines by a one‐pot reductive amination using pyrrolidine as imine‐formation catalyst. The reactions worked with low catalyst loadings in very mild conditions. The procedure is operationally simple and tolerates a wide range of functional groups
A general Pd-catalyzed α- and γ-benzylation of aldehydes for the formation of quaternary centers
作者:Ivan Franzoni、Laure Guénée、Clément Mazet
DOI:10.1039/c5ob00702j
日期:——
A palladium-catalyzed benzylation of α-branched aldehydes has been developed using benzyl methyl carbonates. The method gives access to congested quaternary centers in the vicinity of one of the most sensitive carbonyl functionalities and displays unprecedented generality with respect to both coupling partners. Evidence for the direct involvement of a Pd-η3-benzyl intermediate is provided. Extension
Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes
作者:Samuel L. Bourne、Matthew O'Brien、Sivarajan Kasinathan、Peter Koos、Päivi Tolstoy、Dennis X. Hu、Roderick W. Bates、Benjamin Martin、Berthold Schenkel、Steven V. Ley
DOI:10.1002/cctc.201200778
日期:2013.1
Two tandem flowchemistry processes have been developed. A single palladium‐catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi‐functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium‐catalysed
Synthesis of rac-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:mi>α</mml:mi></mml:math>-aryl propionaldehydes via branched-selective hydroformylation of terminal arylalkenes using water-soluble Rh-PNP catalyst
the substitute on phenyl ring of ligands. These ligands were incorporated into water-soluble rhodium-PNP complex catalysts that were used to regioselective hydroformylation of a series of terminal arylalkenes, providing efficient access to rac-α-aryl propionaldehydes in good to excellent yield (up to 97%) and branched-regioselectivity (up to 40:1 b/l ratio). Furthermore, gram-scale and diverse synthetic
这项工作详细介绍了一类水溶性 PNP 配体的制备,这些配体因配体苯环上取代物的性质而异。这些配体被掺入水溶性铑-PNP络合物催化剂中,用于一系列末端芳基烯烃的区域选择性加氢甲酰化,从而以良好至极好的收率(高达 97%)和支链-区域选择性(高达 40:1 b / l比率)。此外,克级和多样化的合成转化证明了该方法在非甾体抗炎药中的合成应用。
Diastereofacial selectivity via aldol reactions using ethyl dithioacetate and ethyl dithiopropionate enolates
作者:A.I. Meyers、Robert D. Walkup
DOI:10.1016/s0040-4020(01)96754-7
日期:1985.1
The lithium enolate of ethyldithioacetate reacts with α-methyl aldehydes to yield the aldol products in which the syn configuration in the positions β and γ to the thiocarbonyl of the product is favored over the anti configuration. This selectivity is solvent-dependent, and is enhanced at lower temperatures. In most cases, syn:anti product ratios obtained under these conditions varied from 57:43 to