A Comprehensive Study on Metal Triflate-Promoted Hydrogenolysis of Lactones to Carboxylic Acids: From Synthetic and Mechanistic Perspectives
作者:Rui Zhu、Ju-Long Jiang、Xing-Long Li、Jin Deng、Yao Fu
DOI:10.1021/acscatal.7b01569
日期:2017.11.3
could efficiently hydrogenate lactones to carboxylicacids under extra mild conditions (e.g., a reaction temperature of <150 °C and 1 atm of H2) and showed a broad substrate scope. In addition, the catalytic protocol can be further applied to the hydrogenolysis of polyhydroxyalkanoate, as a renewable polymer, to the corresponding straight-chain carboxylicacids. An extensive mechanistic study was subsequently
内酯直接氢解为羧酸(即不接触羰基的C烷氧基-O键的氢解)通常是困难的,因为当前使用布朗斯台德酸作为催化剂的策略通常需要苛刻的条件,例如高温和高温H 2压力。在此,我们报告了已开发的无溶剂催化转化方法,其中W(OTf)6被认为可以促进氢解过程。该策略可以在特别温和的条件下(例如,反应温度<150°C和1 atm H 2的条件下)有效地将内酯氢化为羧酸),并显示出较宽的基材范围。另外,该催化方案可以进一步应用于作为可再生聚合物的聚羟基链烷酸酯的氢解成相应的直链羧酸。随后进行了广泛的机理研究,密度泛函理论计算揭示了一种反应模式,包括在W(OTf)6的帮助下C═O键的完全裂解催化剂。此外,通过电喷雾电离质谱已成功检测到该机理中产生的关键中间体,即具有OTf部分的moiety。通过与布朗斯台德酸催化体系的比较,研究证实了OTf部分的存在可以显着降低与重排和消除过程相关的障碍。同时,重点放在阴离子发挥
Transition Metal‐Free Reduction of Activated Alkenes Using a Living Microorganism
作者:Richard C. Brewster、Jack T. Suitor、Adam W. Bennett、Stephen Wallace
DOI:10.1002/anie.201903973
日期:2019.9.2
chemical synthesis via metabolic engineering. However, despite an increasing interest in the use of de novo metabolic pathways and designer whole-cells for small molecule synthesis, the inherent synthetic capabilities of native microorganisms remain underexplored. Herein, we report the use of unmodified E. coli BL21(DE3) cells for the reduction of keto-acrylic compounds and apply this whole-cell biotransformation
Synthesis of unstrained Criegee intermediates: inverse α-effect and other protective stereoelectronic forces can stop Baeyer–Villiger rearrangement of γ-hydroperoxy-γ-peroxylactones
作者:Vera A. Vil'、Yana A. Barsegyan、Leah Kuhn、Maria V. Ekimova、Egor A. Semenov、Alexander A. Korlyukov、Alexander O. Terent'ev、Igor V. Alabugin
DOI:10.1039/d0sc01025a
日期:——
by exploring the interplay between the primary and secondary stereoelectronic effects in the Baeyer–Villiger (BV) rearrangement by experimental and computationalstudies of γ-OR-substituted γ-peroxylactones, the previously elusive non-strained Criegee intermediates (CI). These new cyclic peroxides were synthesized by the peroxidation of γ-ketoesters followed by in situ cyclization using a BF3·Et2O/H2O2
在从不稳定的中间体中消除立体声电子保护时,我们可以将限制推到多远?我们通过对γ-OR取代的γ-过氧内酯(以前难以捉摸的Criegee中间体(CI))进行实验和计算研究,探索了Baeyer-Villiger(BV)重排中主要和次要立体电子效应之间的相互作用,从而解决了这个问题。 。这些新的环状过氧化物是通过γ-酮酸酯的过氧化反应,然后使用BF 3 ·Et 2 O / H 2 O 2系统原位环化而合成的。尽管主要影响(迁移的C–R m的排列带有断裂的O–O键的碳键在6元环中具有活性,次级作用的减弱(从OR孤对到断裂的C–R m键的捐赠)提供了足够的动力学稳定性,从而允许形成和分离稳定的γ-氢过氧-γ-过氧内酯,在C6-位带有甲基取代基。此外,源于两个新的立体电子因素的反应物稳定化也提供了补充保护,这两个因素在本工作中首次被确定和量化。首先,对γ-氢过氧-γ-过氧内酯的意料之外的偏爱削弱了主要的立体电子效应,并引入了约2
Enzymatic resolution of 3-substituted-4-oxoesters.
The lipase catalyzed hydrolysis of cyanomethyl 3-substituted-4-oxoesters was studied. With 3-methyl substituted esters, PPL led to optically active compounds. When the 3-substituent was a larger group, more satisfactory results were obtained with PL, especially if the substituent attached to the ketone function is other from methyl.