Synthesis of Chromones through LiO<i>t</i>Bu/Air-Mediated Oxidation and Regioselective Cyclization of<i>o</i>-Hydroxyphenyl Propargyl Carbinols
作者:Shuai Zhang、Changfeng Wan、Qiang Wang、Baiqun Zhang、Lingfeng Gao、Zhenggen Zha、Zhiyong Wang
DOI:10.1002/ejoc.201201665
日期:2013.4
A cascade oxidativecyclization reaction for the synthesis of chromone derivatives was developed by using LiOtBu as a mediator and air as an oxidant. The reaction was carried out without the assistance of a transition metal under mild conditions to afford the chromones in good yields with high regioselectivities.
Solvent-directed intramolecular hydrofunctionalization of readily available o-alkynoylphenols 1 was successfully achieved under reagent-free conditions. The hydrofunctionalization of 1 occurred by nucleophilic attack on the phenolic oxygen followed by consecutive migration of the phenolic H atom to the alkyne center, eventually affording γ-benzopyranones 2. The phenol O–H group forms intramolecular H-bonds
在无试剂条件下成功实现了容易获得的邻炔基酚1的溶剂导向分子内氢官能化。1的氢官能化通过对酚氧的亲核攻击随后酚氢原子连续迁移到炔烃中心而发生,最终得到 γ-苯并吡喃酮2。酚 O-H 基团与羰基形成分子内 H 键,我们预测这些 H 键在极性溶剂存在下可以扭曲成它们最优选的构象。区域选择性 6 -endo-dig环化似乎在热力学上优于 5 -exo-dig循环化,由 DFT 计算支持。该策略之所以引人注目,是因为它无试剂、区域选择性、原子经济性高、原子、碳和反应质量效率高。
Metal-free, visible-light-induced C(sp2)-H functionalization/C O bond formation for the synthesis of flavones using air as an oxidant
A green and practical method for synthesizing high value-added flavones from readily available chalcones based on visible-light-induced C(sp2)-H functionalization /CO bondformation is described. This reaction utilizes organic dye (Rose Bengal) as the photosensitizer and atmospheric oxygen as the green oxidant and oxygen source without any metals and external additive requirement. Through this methodology
描述了一种基于可见光诱导的 C(sp 2 )-H 功能化/C O 键形成,从现成的查耳酮合成高附加值黄酮的绿色实用方法。该反应以有机染料(玫瑰红)为光敏剂,大气中的氧气为绿色氧化剂和氧源,无需任何金属和外加剂。通过这种方法,以中等到良好的收率合成了多种黄酮。
Parikh; Shah, Journal of the Indian Chemical Society, 1959, vol. 36, p. 729