Diastereomeric Preparation of a- and b-Phenylthio Substituted N-Acylpyrazoles
摘要:
When 3-phenyl-l-menthopyrazole was used as a chiral auxiliary, the diastereomeric preparation of alpha- and beta-phenylthio-substituted N-acylpyrazoles (4 and 9) was accomplished in high yield by the alpha-sulfenylation using diphenyl disulfide and the conjugate addition of thiophenol, respectively.
Catalytic, Enantioselective Addition of Alkyl Radicals to Alkenes via Visible-Light-Activated Photoredox Catalysis with a Chiral Rhodium Complex
作者:Haohua Huo、Klaus Harms、Eric Meggers
DOI:10.1021/jacs.6b03399
日期:2016.6.8
An efficient enantioselective addition of alkyl radicals, oxidatively generated from organotrifluoroborates, to acceptor-substituted alkenes is catalyzed by a bis-cyclometalated rhodium catalyst (4 mol %) under photoredox conditions. The practical method provides yields up to 97% with excellent enantioselectivities up to 99% ee and can be classified as a redox neutral, electron-transfer-catalyzed reaction
Photocatalytic Giese Addition of 1,4-Dihydroquinoxalin-2-ones to Electron-Poor Alkenes Using Visible Light
作者:Jaume Rostoll-Berenguer、Gonzalo Blay、José R. Pedro、Carlos Vila
DOI:10.1021/acs.orglett.0c02953
日期:2020.10.16
The optimized reaction conditions provide a good yield for the radical conjugate addition products (44 examples) with a wide range of structurally different Michael acceptors. A gram scale reaction using sunlight irradiation is also described. Furthermore, several transformations were carried out with the Giese addition products.
使用Ru(bpy)3 Cl 2作为光催化剂和(PhO)2 PO 2 H作为添加剂,实现了1,4-二氢喹喔啉-2-酮与Michael受体的可见光光氧化还原催化偶联。优化的反应条件为具有广泛结构上不同的迈克尔受体的自由基共轭加成产物(44个实例)提供了良好的收率。还描述了使用阳光照射的克级反应。此外,使用Giese添加产品进行了几次转化。
Catalytic Enantioselective Synthesis of Protecting-Group-Free 1,5-Benzothiazepines
作者:Sara Meninno、Chiara Volpe、Alessandra Lattanzi
DOI:10.1002/chem.201700837
日期:2017.4.3
2,3‐dihydro‐1,5‐benzothiazepinones, by an organocatalyzed sulfa‐Michael reaction of readily available α,β‐unsaturated N‐acyl pyrazoles with 2‐aminothiophenols followed by silica‐gel‐catalyzed lactamization, has been developed. The method proceeds under mild conditions at room temperature and it requires only 1 mol % catalyst loading, to give 2‐aryl/alkyl‐substituted 1,5‐benzothiazepines in generally
Conjugate addition of grignard reagents to<i>N</i>-(α,β-unsaturated)acylpyrazoles. Diastereoselective β-alkylation using 3-phenyl-<i>l</i>-menthopyrazole
The conjugate additions of N-(α,β-unsaturated)acylpyrazoles were carried out by the treatment with Grignardreagents in the presence of cuprous halides. The reaction of 2-(α,β-unsaturated)acyl-3-phenyl-l-menthopyrazoles 3a-h occurred in higher chemical yields and with asymmetric inductions on β-position, where the addition of magnesium bromide as a Lewis acid influenced to the yields and the diastereoselectivities
According to four different methods, various types of N-acylpyrazoles were prepared from the corresponding pyrazoles and carboxylic acids or their acid chlorides. Although N-acylpyrazoles were inert to alcohols under neutral or weakly basic conditions, the alcoholysis was dramatically accelerated by the action of strong acid or base. On the basis of these chemical properties, the regioselective synthesis of methyl benzyl 2,2-dimethylglutarate was achieved by selective protection and functionalization of a carboxylic acid derivative using N-acylpyrazoles.