作者:Nanda D. Paul、Sutanuva Mandal、Matthias Otte、Xin Cui、X. Peter Zhang、Bas de Bruin
DOI:10.1021/ja4111336
日期:2014.1.22
Cobalt(III)-carbene radicals, generated through metalloradical activation of salicyl N-tosylhydrazones by cobalt(II) complexes of porphyrins, readily undergo radical addition to terminal alkynes to produce salicyl-vinyl radical intermediates. Subsequent hydrogen atom transfer (HAT) from the hydroxy group of the salicyl moiety to the vinyl radical leads to the formation of 2H-chromenes. The Co(II)-catalyzed
钴(III)-卡宾自由基是通过卟啉钴(II)配合物对水杨基N-甲苯磺酰腙进行金属自由基活化而产生的,很容易与末端炔进行自由基加成,产生水杨基-乙烯基自由基中间体。随后氢原子从水杨基部分的羟基转移(HAT)至乙烯基,导致2H-色烯的形成。Co(II) 催化的过程可以耐受各种取代模式,并以良好的分离收率生产相应的 2H-色烯产物。EPR 光谱和 TEMPO 自由基捕获实验与所提出的自由基机制一致。DFT 计算揭示了通过金属自由基介导的过程形成水杨基-乙烯基自由基中间体。出乎意料的是,随后从羟基部分到乙烯基的 HAT 导致形成邻醌甲基化物中间体,该中间体自发地从钴中心解离,并很容易进行环内、σ 闭环反应,形成最终的 2H-色烯产物。
Direct Synthesis of 2-Methylbenzofurans from Calcium Carbide and Salicylaldehyde <i>p</i>-Tosylhydrazones
作者:Rugang Fu、Zheng Li
DOI:10.1021/acs.orglett.8b00676
日期:2018.4.20
A new methodology for the construction of methyl-substituted benzofuran rings from the reactions of calcium carbide with salicylaldehyde p-tosylhydrazones/2-hydroxyacetophenone p-tosylhydrazones is described. Various 2-methylbenzofurans and 2,3-dimethylbenzofurans could be obtained in satisfactory yield by using a cuprous chloride catalyst. The advantages of this protocol include the use of a readily
Palladium-Catalyzed Tandem Reaction of Alkyne-Based Aryl Iodides and Salicyl<i>N</i>-Tosylhydrazones to Construct the Spiro[benzofuran-3,2′-chromene] Skeleton
作者:Xue Song Shang、Nian Tai Li、Deng Yuan Li、Pei Nian Liu
DOI:10.1002/adsc.201501150
日期:2016.5.19
aryl iodides and salicyl N‐tosylhydrazones has been achieved to afford a series of compounds containing the novel spiro[benzofuran‐3,2′‐chromene] scaffold in moderate to good yields. This efficient catalytic reaction, which tolerates various functional groups, combines alkyne‐based 5‐exo‐dig cyclization, palladium(II) carbene migratory insertion and intramolecular cyclization, generating three new bonds
A method was developed for the preparation of 3-(2,2-dichloroacetyl)-2H-chromen-2-ones and (E)-N′-(2-hydroxybenzylidene)-N,4-dimethylbenzenesulfono hydrazides by reacting salicyl N-tosylhydrazones with ethyl 4,4,4-trichloro-3-oxobutanoate and dimethyl (1-diazo-2-oxopropyl)-phosphonate (Bestmann-Ohira reagent) in presence of RuCl3 ⋅ 3H2O.
Palladium-Catalyzed Tandem Carbene Migratory Insertion and Intramolecular Cyclization: Synthesis of Chromeno[4,3-<i>b</i>]chromene Compounds
作者:Xue Song Shang、Nian Tai Li、Hai Xiao Siyang、Pei Nian Liu
DOI:10.1021/acs.joc.5b00500
日期:2015.5.1
Chromeno[4,3-b]chromene is a ubiquitous structural motif found in various pharmaceuticals and biologically active compounds. A concise palladium-catalyzed reaction of vinyl iodides and salicyl N-tosylhydrazones has been achieved to afford a series of compounds containing the chromeno[4,3-b]chromene scaffold in moderate to high yield. This tandem reaction involves palladium(II) carbene migratory insertion and intramolecular cyclization assisted by an O nucleophile and tolerates various functional groups.