developed by using tubular carbonnitride (TCN) as a general heterogeneous photocatalyst under an oxygen atmosphere with visiblelight irradiation. This protocol has an excellent substrate scope and gives the desired aldehydes, ketones and esters in moderate to high yields. Importantly, this metal-free procedure employed photogenerated hydroxyl radicals in situ as green oxidation active species, avoiding
Experimental and Theoretical Studies on Gas-Phase Fragmentation Reactions of Protonated Methyl Benzoate: Concomitant Neutral Eliminations of Benzene, Carbon Dioxide, and Methanol
作者:Hanxue Xia、Yong Zhang、Athula B. Attygalle
DOI:10.1007/s13361-018-1997-8
日期:2018.8.1
a methanol molecule after a protonation on the methoxy group. The incipient proton migrates to the ring and randomizes to a certain degree before a subsequent transfer of one of the ring protons to the alkoxy group for the concomitant methanol elimination. The spectrum recorded from deuteronated methyl benzoate showed two peaks at m/z 105 and 106 for the benzoyl cation at a ratio of 2:1, confirming
活化后,质子化的苯甲酸甲酯通过三个不同的途径断裂。对通过氦等离子体电离(HePI)生成的质子化物质的m / z 137离子进行了质量选择,并进行了碰撞活化。在一个断裂途径中,质子化的分子通过消除苯分子产生了m / z 59的产物离子(途径I)。该M / Z以这种方式产生的59离子(通常被认为是甲氧羰基阳离子),然后通过脱羧原位形成甲基碳正离子,然后通过分子过程在苯环上引发亲电芳族加成反应,生成甲苯阳离子(途径II)。此外,质子化的苯甲酸甲酯也经历甲醇损失(途径III)。然而,在甲氧基上质子化之后,不是简单地除去甲醇分子。初始质子迁移至环并随机化至一定程度,然后环质子之一随后转移至烷氧基以伴随甲醇消除。氘化苯甲酸甲酯记录的光谱在m / z处显示两个峰苯甲酰基阳离子的比率为105和106,比率为2:1,这证明赋予电荷的质子是可移动的。然而,在达到完全加扰状态之前,发生了从苯中间体中间质子转移至甲氧基的甲醇损失。
Intermolecular Carbonyl–olefin Metathesis with Vinyl Ethers Catalyzed by Homogeneous and Solid Acids in Flow
作者:Miguel Ángel Rivero‐Crespo、María Tejeda‐Serrano、Horacio Pérez‐Sánchez、José Pedro Cerón‐Carrasco、Antonio Leyva‐Pérez
DOI:10.1002/anie.201909597
日期:2020.3.2
carbonyl-olefin metathesis of aromatic ketones and aldehydes with vinyl ethers in-flow, to give alkenes with complete trans stereoselectivity on multi-gram scale and high yields. Experimental and computational data support a mechanism based on a carbocation-induced Grob fragmentation. These results open the way for the industrial implementation of carbonyl-olefin metathesisover solid catalysts in continuous
Nucleophilic Catalysis with 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) for the Esterification of Carboxylic Acids with Dimethyl Carbonate
作者:Wen-Chung Shieh、Steven Dell、Oljan Repič
DOI:10.1021/jo011036s
日期:2002.4.1
0]undec-7-ene (DBU) is an effective nucleophilic catalyst for carboxylic acid esterification with dimethyl carbonate (DMC). The reaction pathway of this new class of nucleophilic catalysis has been studied. A plausible, multistep mechanism is proposed, which involves an initial N-acylation of DBU with DMC to form a carbamate intermediate. Subsequent O-alkylation of the carboxylate with this intermediate