Chemoenzymatic one-pot reaction of noncompatible catalysts: combining enzymatic ester hydrolysis with Cu(<scp>i</scp>)/bipyridine catalyzed oxidation in aqueous medium
作者:Henning Sand、Ralf Weberskirch
DOI:10.1039/c7ra05451c
日期:——
chemoenzymatic one-pot reactions in aqueousmedia remain challenging and are limited today to metal-catalysts that display high activity in aqueousmedia. Here, we report the first combination of two incompatible catalytic systems, a lipase based ester hydrolysis with a water-sensitive Cu/bipyridine catalyzed oxidation reaction, in a one-pot reaction in aqueous medium (PBS buffer). Key to the solution
The formyloxyl radical: electrophilicity, C–H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
作者:Miriam Somekh、Mark A. Iron、Alexander M. Khenkin、Ronny Neumann
DOI:10.1039/d0sc04936k
日期:——
outer-sphere electrontransfer between the formyloxyl radical donor and the [CoIIIW12O40]5− polyanion acceptor forming a donor–acceptor [D+–A−] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O˙ towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes
过去,很少通过实验观察到甲酰氧基自由基HC(O)O 3,这些研究是在电子结构的背景下进行的理论光谱分析。缺乏方便的制备甲酰氧基自由基的方法,使得人们无法研究其对有机底物的反应性。最近,我们发现在甲酸/甲酸锂的阳极电化学氧化中形成了HC(O)O 3。使用[Co III W 12 O 40 ] 5-聚阴离子催化剂,可导致由苯形成甲酸苯酯。在这里,我们介绍我们对电化学原位反应性的研究用有机底物生成HC(O)O 3。根据实验和计算得出的哈米特线性自由能关系,与苯的反应和选择的取代衍生物表明,HC(O)O 3是亲电子的。HC(O)O 3与末端烯烃的反应明显有利于抗马尔可夫尼科夫氧化反应,产生相应的醛作为主要产物以及进一步的氧化产物。以1-己烯为代表的底物进行的可能的反应路径分析,有利于从烯丙基C–H键中抽出氢形成己烯丙基的可能性,然后强烈建议在C1位置进一步进攻第二个HC(O)O˙自由基。据推测,进一步的氧化产物主要是由于HC(O)O
Direct Catalytic Enantioselective Benzylation from Aryl Acetic Acids
作者:Patrick J. Moon、Zhongyu Wei、Rylan J. Lundgren
DOI:10.1021/jacs.8b11390
日期:2018.12.19
We demonstrate that metal-catalyzed enantioselective benzylation reactions of allylic electrophiles can occur directly from aryl acetic acids. The reaction proceeds via a pathway in which decarboxylation is the terminal event, occurring after stereoselective carbon-carbon bond formation. This mechanistic feature enables enantioselective benzylation without the generation of a highly basic nucleophile
Synthesis of Diastereomerically and Enantiomerically Pure 2,3-Disubstituted Tetrahydrofurans Using a Sulfoxonium Ylide
作者:Jennifer M. Schomaker、Veera Reddy Pulgam、Babak Borhan
DOI:10.1021/ja0469075
日期:2004.10.1
via Sharpless asymmetric epoxidation chemistry, offer access to a wide variety of enantiomerically pure compounds. In this communication, we describe the use of a Payne rearrangement to control regioselectivity in the ring-opening of a series of 2,3-epoxy alcohols with dimethylsulfoxonium methylide to yield diastereomerically and/or enantiomerically pure disubstituted tetrahydrofuran rings. The factors
Chemoselective hydrogen peroxide oxidation of allylic and benzylic alcohols under mild reaction conditions catalyzed by simple iron-picolinate complexes
作者:Shinji Tanaka、Yoshihiro Kon、Takuya Nakashima、Kazuhiko Sato
DOI:10.1039/c4ra05819d
日期:——
Chemoselective oxidation of allylic alcohols to α,β-unsaturated carbonyl compounds proceeded efficiently using hydrogen peroxide with iron-picolinate catalysts. The in situ generated [Fe(Me-Pic)3] (Me-Pic = 6-methylpicolinate) catalyzed oxidation of the alcohol moiety of primary allylic alcohols while the [Fe(Pic)3] (Pic = picolinate) and [Fe(Me-Pic)2(Pic)] did not show sufficient catalytic activity