Visible Light-Induced Decarboxylative Acylarylation of Phenyl Propiolates with α-Oxocarboxylic Acids to Coumarins Catalyzed by Hypervalent Iodine Reagents under Transition Metal-Free Conditions
作者:Shuai Yang、Hui Tan、Wangqin Ji、Xiangbiao Zhang、Pinhua Li、Lei Wang
DOI:10.1002/adsc.201600721
日期:2017.2.2
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Visible-Light-Promoted Dual C–C Bond Formations of Alkynoates via a Domino Radical Addition/Cyclization Reaction: A Synthesis of Coumarins
作者:Shangbiao Feng、Xingang Xie、Weiwei Zhang、Lin Liu、Zhuliang Zhong、Dengyu Xu、Xuegong She
DOI:10.1021/acs.orglett.6b01857
日期:2016.8.5
difunctionalization of alkynoates has been accomplished. This procedure provides a new strategy toward synthesis of the coumarin core structure by photoredox-mediated oxidation to generate the α-oxo radical, which supervenes a dominoradical addition/cyclization reaction in moderate to good yields with high regioselectivity at ambient temperature.
An efficientone-pot stepwise method to synthesize 3-styryl-4-arylcoumarins from simple alkynoates is demonstrated. On the basis of the control experiments, a possible mechanism involving light-driven radical cyclization and Pd-catalysed cross-coupling processes for this synthesismethod is proposed. The results of X-ray analysis and spectroscopy experiments prove that the substituent effect has a
Water-removable ynamide coupling reagent for racemization-free syntheses of peptides, amides, and esters
作者:Tao Liu、Xue Zhang、Zejun Peng、Junfeng Zhao
DOI:10.1039/d1gc03498g
日期:——
A novel ynamide coupling reagent, the by-product of which can be removed by water, was reported. It promotes the direct coupling between carboxylic acids and amines, alcohols or thiols to provide amides, peptides, esters and thioesters, respectively. No detectable racemization was observed for all the coupling reactions of carboxylic acids containing an α-chiral center. Importantly, a simple acidic
oxidative difunctionalization of aryl alkynoates at room temperature to access stereodefined fully substituted α,β-unsaturated acids bearing a chalcogen functionality in high yields (up to 95%). The protocol is operationally simple, metal-free, scalable, and suppresses the usual CO2 exclusion phenomenon. The utility of this method was showcased in the synthesis of vinyl halides, vinyl selenides, and