Chemo- and Regioselective Synthesis of Acyl-Cyclohexenes by a Tandem Acceptorless Dehydrogenation-[1,5]-Hydride Shift Cascade
作者:Lewis B. Smith、Roly J. Armstrong、Daniel Matheau-Raven、Timothy J. Donohoe
DOI:10.1021/jacs.9b12296
日期:2020.2.5
acceptorless dehydrogenation of the diol followed by a redox-neutral cascade process, which is independent of the iridium catalyst. Deuteriumlabelingstudies established that the key step of this cascade involves a novel base-mediated [1,5]-hydride shift. The cyclohexenyl ketone products could readily be cleaved under mildly acidic conditions to access a range of valuable substituted cyclohexene derivatives
描述了一种从五甲基苯乙酮和 1,5-二醇中获得取代的酰基环己烯的原子经济方法。该过程由铱 (I) 催化剂与庞大的富电子膦配体 (CataCXium A) 共同催化,该配体有利于无受体脱氢反应,而不是共轭还原成相应的环己烷。该反应产生水和氢气作为唯一的副产物,并且可以使用该方法以非常高的产率合成范围广泛的官能化酰基环己烯产物。进行了一系列对照实验,结果表明该过程是由二醇的无受体脱氢引发的,然后是氧化还原中性级联过程,该过程与铱催化剂无关。氘标记研究表明,该级联的关键步骤涉及一种新型碱介导的 [1,5]-氢化物转移。环己烯基酮产物在弱酸性条件下很容易裂解,以获得一系列有价值的取代环己烯衍生物。
Catalytic Asymmetric Synthesis of Cyclohexanes by Hydrogen Borrowing Annulations
作者:Roly J. Armstrong、Wasim M. Akhtar、Tom A. Young、Fernanda Duarte、Timothy J. Donohoe
DOI:10.1002/anie.201907514
日期:2019.9.2
Hydrogen borrowing catalysis serves as a powerful alternative to enolate alkylation, enabling the direct coupling of ketones with unactivated alcohols. However, to date, methods that enable control over the absolute stereochemical outcome of such a process have remained elusive. Here we report a catalytic asymmetric method for the synthesis of enantioenriched cyclohexanes from 1,5‐diols via hydrogen
(o-PPh2C6H4NHR)2RuCl2 (R = Me, 3; Et, 4; CH2Ph, 5) and (o-PPh2C6H4NH2)[(CH2NHR)2]RuCl2 (R = Me, 7; Et, 8; iPr, 9) modulated with mono-N-functionalized secondary amino ligands were synthesized and demonstrated as efficient catalysts in the hydrogenation of esters into alcohols. The catalytic performances of these new complexes are much better than their corresponding primary amino ligand-constituted complexes (o-PPh2C6H4NH2)2RuCl2
一系列钌配合物(o -PPh 2 C 6 H 4 NHR)2 RuCl 2(R = Me,3 ; Et,4 ; CH 2 Ph,5)和(o -PPh 2 C 6 H 4 NH 2)[ (CH 2 NHR)2 ] RuCl 2(R = Me,7 ; Et,8 ; iPr,9)调制的单氮原子合成了功能化的仲氨基配体,并证明了其为酯加氢成醇的有效催化剂。这些新的配合物的催化性能远远优于其相应的伯氨基配体构成的配合物(o -PPh 2 C 6 H 4 NH 2)2 RuCl 2(2)和(o -PPh 2 C 6 H 4 NH 2) [(CH 2 NH 2)2 ] RuCl 2(6)。与伯氨基配体相比,显着改善归因于仲氨基配体的电子密度增加。
Acetylation and formylation of alcohols with triphenylphosphine and carbon tetrabromide in ethyl acetate or ethyl formate
Alcohols were acetylated or formylated with triphenylphosphine and carbon tetrabromide in ethylacetate or ethyl (or methyl) formate at room temperature. THP or TBDMS ether of primary alcohol got converted into formate or acetate under the experimental conditions employed in one pot operation.
Primary and secondaryalcohols are acylated under mild conditions by the use of 2,2′-bipyridyl-6-yl carboxylates and cesium fluoride. Furthermore, the reaction is successfully applied to selectiveacylation of a primary carbinol group of diols containing primary and secondary carbinol groups or exclusive O-acylation of aromatic amino alcohols.