排序方式: 共有13条查询结果,搜索用时 15 毫秒
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Holly V. Adcock Elli Chatzopoulou Paul W. Davies 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(51):15745-15749
Gold carbene reactivity patterns were accessed by ynamide insertion into a C(sp3) H bond. A substantial increase in molecular complexity occurred through the cascade polycyclization of N‐allyl ynamides to form fused nitrogen‐heterocycle scaffolds. Exquisite selectivity was observed despite several competing pathways in an efficient gold‐catalyzed synthesis of densely functionalized C(sp3)‐rich polycycles and a copper‐catalyzed synthesis of fused pyridine derivatives. The respective gold–keteniminium and ketenimine activation pathways have been explored through a structure–reactivity study, and isotopic labeling identified turnover‐limiting C H bond‐cleavage in both processes. 相似文献
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Nicholas D. C. Tappin Weronika Michalska Simon Rohrbach Philippe Renaud 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14378-14382
An operationally simple method to affect an atom‐transfer radical addition of commercially available ICH2Bpin to terminal alkenes has been developed. The intermediate iodide can be transformed in a one‐pot process into the corresponding cyclopropane upon treatment with a fluoride source. This method is highly selective for the cyclopropanation of unactivated terminal alkenes over non‐terminal alkenes and electron‐deficient alkenes. Due to the mildness of the procedure, a wide range of functional groups such as esters, amides, alcohols, ketones, and vinylic cyclopropanes are well tolerated. 相似文献
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Dr. Yongquan Ning Xinyu Zhang Yi Gai Yuanqing Dong Dr. Paramasivam Sivaguru Yingying Wang Dr. Bhoomireddy Rajendra Prasad Reddy Prof. Giuseppe Zanoni Prof. Xihe Bi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6535-6543
Despite the growing importance of volatile functionalized diazoalkanes in organic synthesis, their safe generation and utilization remain a formidable challenge because of their difficult handling along with storage and security issues. In this study, we developed a bench-stable difluoroacetaldehyde N-triftosylhydrazone (DFHZ-Tfs) as an operationally safe diazo surrogate that can release in situ two low-molecular-weight diazoalkanes, diazoacetaldehyde (CHOCHN2) or difluorodiazoethane (CF2HCHN2), in a controlled fashion under specific conditions. DFHZ-Tfs has been successfully employed in the Fe-catalyzed cyclopropanation and Doyle–Kirmse reactions, thus highlighting the synthetic utility of DFHZ-Tfs in the efficient construction of molecule frameworks containing CHO or CF2H groups. Moreover, the reaction mechanism for the generation of CHOCHN2 from CF2HCHN2 was elucidated by density functional theory (DFT) calculations. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1632-1635
The first stereoconvergent cyclopropanation reaction by means of photoredox catalysis using diiodomethane as the methylene source is described. This transformation exhibits broad functional group tolerance and it is characterized by an excellent stereocontrol en route to trans ‐cyclopropanes regardless of whether E‐ or Z ‐styrene substrates were utilized. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(3):855-859
Electron‐rich diazo compounds, such as aryldiazomethanes, are powerful reagents for the synthesis of complex structures, but the risks associated with their toxicity and instability often limit their use. Flow chemistry techniques make these issues avoidable, as the hazardous intermediate can be used as it is produced, avoiding accumulation and handling. Unfortunately, the produced stream is often contaminated with other reagents and by‐products, making it incompatible with many applications, especially in catalysis. Herein is reported a metal‐free continuous flow method for the production of aryldiazomethane solutions in a non‐coordinating solvent from easily prepared, bench‐stable sulfonylhydrazones. All by‐products are removed by an in‐line aqueous wash, leaving a clean, base‐free diazo stream. Three successful sensitive metal‐catalyzed transformations demonstrated the value of the method. 相似文献
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Tristan Chidley Islam Jameel Shafa Rizwan Philippe A. Peixoto Laurent Pouysgu Stphane Quideau W. Scott Hopkins Graham K. Murphy 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17115-17121
A facile and highly chemoselective synthesis of doubly activated cyclopropanes is reported where mixtures of alkenes and β‐dicarbonyl‐derived iodonium ylides are irradiated with light from blue LEDs. This metal‐free synthesis gives cyclopropanes in yields up to 96 %, is operative with cyclic and acyclic ylides, and proceeds with a variety of electronically‐diverse alkenes. Computational analysis explains the high selectivity observed, which derives from exclusive HOMO to LUMO excitation, instead of free carbene generation. The procedure is operationally simple, uses no photocatalyst, and provides access in one step to important building blocks for complex molecule synthesis. 相似文献
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