Promising levels of enantiocontrol are observed in the silanediol-catalyzed addition of silyl ketene acetals to benzopyrylium triflates. This rare example of enantioselective, intermolecular chromenone functionalization with carbonyl containing nucleophiles has potential applications in the synthesis of bioactive chromanones and tetrahydroxanthones.
Efficient Synthesis of Chromones with Alkenyl Functionalities by the Heck Reaction
作者:Tamás Patonay、Attila Vasas、Attila Kiss-Szikszai、Artur M. S. Silva、José A. S. Cavaleiro
DOI:10.1071/ch10295
日期:——
the Heck reaction in the field of chromones has been demonstrated. Bromochromones with the halogen atom in their rings A and B were reacted with various terminal alkenes to give hitherto unknown alkenyl‐substituted chromones. Reactivity of the substrates was found to markedly depend on the position of the bromineatom. Under phosphine‐free conditions using a phase‐transfer catalyst additive (tetrabutylammonium
NIS/TBHP Induced Regioselective Selenation of (Hetero)Arenes
<i>via</i>
Direct C−H Functionalization
作者:Chaochao Ding、Yuanzu Yu、Qiongli Yu、Zixin Xie、Yan Zhou、Jianmin Zhou、Guang Liang、Zengqiang Song
DOI:10.1002/cctc.201801548
日期:2018.12.7
A simple and efficient method for the regioselective selenation of (hetero)arenes via direct C−Hfunctionalization has been established using NIS and TBHP. The present protocol is compatible with different functional groups, and suitable for various (hetero)arenes and diselenides, efficiently affording the desired products in moderate to excellent yields.
Metal-free synthesis of novel indolizines from chromones and pyridinium salts via 1,3-dipolar cycloaddition, ring-opening and aromatization
作者:Kai-Kai Dong、Qiang Huang
DOI:10.1016/j.tetlet.2019.04.056
日期:2019.7
efficient, and economical synthetic approach to construct a variety of stucturally novelindolizines bearing a phenolic hydroxy group has been developed through 1,3-dipolar cycloaddition of chromones and pyridinium salts. The methodology is tolerant of a wide range of functional groups and applicable to library synthesis.
Helical Multi‐Coordination Anion‐Binding Catalysts for the Highly Enantioselective Dearomatization of Pyrylium Derivatives
作者:Theresa Fischer、Julia Bamberger、Melania Gómez‐Martínez、Dariusz G. Piekarski、Olga García Mancheño
DOI:10.1002/anie.201812031
日期:2019.3.4
A general and highlyenantioselective synthesis of oxygen heterocycles from readily available in situ generated pyrylium derivatives has been realized by embracing a multi-coordination approach with helical anion-binding tetrakistriazole catalysts. The high activity of the tetrakistriazole (TetraTri) catalysts, with distinct confined anion-binding pockets, allows for remarkably low catalyst loadings