Catalytic Hunsdiecker Reaction of α,β-Unsaturated Carboxylic Acids: How Efficient Is the Catalyst?
摘要:
UV-vis spectrophotometry is utilized to measure the relative efficiency of lithium acetate, tetrabutylammonium. trifluoroacetate, and triethylamine as catalysts for the conversion of 4-methoxycinnamic acid to 4-methoxy-beta-bromostyrene. In acetonitrile-water as solvent, the efficiency order is lithium acetate > triethylamine > tetrabutylammonium trifluoroacetate. For triethylamine as catalyst, solvent-dependent order is acetonitrile-water > dichloromethane > acetonitrile. Using triethylamine as catalyst (5-20 mol %), cinnamic acids, and propiolic acids are converted to corresponding beta-bromostyrenes and 1-halo-1-alkynes in 60-98% isolated yields within 1-5 min.
synthesis of a vast variety of heteroatom‐containing cyclobutene‐triflones [bis(trifluoromethylsulfonyl)cyclobutenes] and cyclobutenones has been developed starting from heteroatom‐substituted alkynes and a pyridinium salt (a latent Tf2C=CH2 source). This powerful methodology, involving cyclization reactions, allows for the selective preparation of oxygen‐, nitrogen‐, bromine‐, chlorine‐, iodine‐, sulfur‐
从杂原子取代的炔烃和吡啶鎓盐(潜在的Tf 2 C = CH 2来源)开始,开发了可控制的无金属合成各种杂原子的环丁烯-triflones [双(三氟甲基磺酰基)环丁烯]和环丁烯酮。。这种强大的方法涉及环化反应,可以选择性地制备氧,氮,溴,氯,碘,硫,硒,碲,磷和硅官能化的环丁烯衍生物。
Highly efficient and recyclable catalyst for the direct chlorination, bromination and iodination of terminal alkynes
作者:Wei Shi、Zhipeng Guan、Peng Cai、Hao Chen
DOI:10.1016/j.jcat.2017.07.019
日期:2017.9
Direct halogenation, including chlorination, bromination and iodination of terminalalkynes, are of great importance in organic synthesis. Here an efficient and recyclable nano-Ag/g-C3N4 catalyst system was developed and proved to be remarkably active with 39 examples varied from chlorination, bromination to iodination, of which 14 runs have yielded more than 95% of the product. Recycling of the catalyst
直接卤化,包括末端炔烃的氯化,溴化和碘化,在有机合成中非常重要。在此,开发了一种有效且可循环利用的纳米Ag / gC 3 N 4催化剂体系,并证明其具有显着的活性,从氯化,溴化到碘化的39种实例中,有14种的收率超过了95%。在几次运行后,也实现了催化剂的再循环而没有明显的活性损失:即使在苯乙炔的溴化过程中进行了5次运行,也观察到99%的收率。该催化剂系统成本低廉且易于制备,使得该方法通用,方便且经济。
Convenient Access to 2,3‐Disubstituted‐cyclobut‐2‐en‐1‐ones under Suzuki Conditions and Their Synthetic Utility
A regioselective synthesis of general applicability has been designed for the one‐pot preparation of 2,3‐disubstituted‐cyclobutenones from iodoalkynes through cyclobutenylation, Suzuki CC coupling, and ketone formation. This one‐pot methodology has been applied to the selective synthesis of an orally active cyclooxygenase II inhibitor. Furthermore, the obtained cyclobut‐2‐en‐1‐ones were used as synthons
palladium-catalyzed cross-coupling reaction of alkynyl halides with organoboronic acidsunderaerobicconditions has been developed. In the presence of bis(dibenzylideneacetone)palladium(0) and cesium carbonate, a variety of alkynyl halides (I, Br, and Cl) underwent the Suzuki-Miyaura cross-coupling reaction with organoboronic acids at room temperature to afford the corresponding unsymmetrical diarylalkynes
Tandem Palladium Catalysis for Rapid Construction of 3,4‐Fused Tricyclic Indoles
作者:Weiyi Wang、Min Yang、Dandan Han、Qiuqin He、Renhua Fan
DOI:10.1002/adsc.201901544
日期:2020.3.17
of a single catalyst to promote two or more mechanistically distinct cycles in onepot to assemble complex organic molecules, is an attractive target. In this paper, we report a reductant‐triggered tandem palladium catalysis process that rapidly assembles 3,4‐fused tricyclic indoles from three readily available starting materials. This tandem process involves a Pd0‐catalyzed in situ coupling/cyclization/Michael