Direct C–C Bond Formation of Allylic Alcohols with CO<sub>2</sub> toward Carboxylic Acids by Photoredox/Nickel Dual Catalysis
作者:Zhengning Fan、Shenhao Chen、Song Zou、Chanjuan Xi
DOI:10.1021/acscatal.2c00418
日期:2022.3.4
Carboxylation of allylic alcohols with carbondioxide is accomplished by photoredox/nickel dual catalysis, generating linear acids exclusively with good Z/E stereoselectivity. Hantzsch ester is employed as the reductant instead of stoichiometric metallic reductants, and the reaction can be conducted under room temperature with a blue LED light source. Mechanisticstudies reveal that the presence of
烯丙醇与二氧化碳的羧基化是通过光氧化还原/镍双重催化完成的,仅生成具有良好Z/E立体选择性的线性酸。采用 Hantzsch 酯代替化学计量的金属还原剂作为还原剂,反应可以在室温下用蓝色 LED 光源进行。机理研究表明,该催化体系中水的存在对反应的成功至关重要,并且反应更有可能在原位形成的烯丙基碳酸氢盐的氧化加成中进行。
A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds
Rhodium-catalyzed decomposition of alpha-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding alpha-silyl, alpha-hydroxy, alpha-alkoxy, alpha-amino, and alpha-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral alpha-vinyldiazoesters and Doyle's chiral catalyst Rh-2(MEPY)(4). In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh-2(MEPY)(4)-catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.
Electron Transfer Profile of Cyclopropanone Acetals in the Nonirradiated Reaction with Tetracyanoethylene, Chloranil, and Dicyanodichlorobenzoquinone
作者:Akira Oku、Manabu Abe、Masaharu Iwamoto
DOI:10.1021/jo00103a043
日期:1994.12
The donor profiles of cyclopropanone acetals 1 and 2 were examined in the reactions with electron accepters (TCNE, DDQ, chloranil, and 1-cyanonaphthalene). With TCNE under nonirradiating conditions, an exclusive 2 + 2 cycloaddition took place stereospecifically with monosubstituted acetals 1a-c but nonstereospecifically with disubstituted acetals 1d,e. With quinones, a ring-opening of the cyclopropane and its coupling with the quinone took place to give the C (cyclopropane)-O (quinone) adduct 9 (with chloranil) or 10 (with DDQ), the latter of which underwent the elimination of a phenol to produce unsaturated esters 5 and 6. In addition, the intervention of the C (cyclopropane)-C (quinone) adduct 14 (with chloranil) or 15 (with DDQ), both as the precursor of 5 and 6, was also postulated. With 1-cyanonaphthalene, under photolysis, the cis/trans isomerization of 1 and 2 occurred. The results provided evidences that cyclopropanone acetals, in general, are prone to function as donors. The mechanism of the reaction with quinones, in particular, was investigated in detail.
MITTELBACH, MARTIN;POKLUKAR, NORBERT, CHEM. AND PHYS. LIPIDS , 55<!>,(1990) N, C. 67-72