One Pot Synthesis of γ-Benzopyranones via Iron-Catalyzed Aerobic Oxidation and Subsequent 4-Dimethylaminopyridine Catalyzed 6-<i>endo</i>
Cyclization
作者:Di Zhai、Lingzhu Chen、Minqiang Jia、Shengming Ma
DOI:10.1002/adsc.201700993
日期:2018.1.4
One-potsynthesis of γ-benzopyranones was realized in decent yields and excellent regioselectivities via iron-catalyzed aerobic oxidation and 4-dimethylaminopyridine-catalyzed cyclization of related propargylic alcohols. Derivatizations to aromatic substituted γ-benzopyranones and synthesis of naturally occurring 3′,4′-dimethoxyflavone have also been realized.
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。
Photochemistry of chromones: photoreorganisation of 3-alkoxy-2-thienyl-4-oxo-4H-1-benzopyrans
作者:Satish C. Gupta、Somesh Sharma、Ashok Saini、Som N. Dhawan
DOI:10.1039/a901090d
日期:——
Photoirradiation of a methanolic solution of 3-alkoxy-2-thienyl-4-oxo-4H-1-benzopyrans with Pyrex filtered UV light leads to cyclised and cyclodehydrogenated angular products involving both thiophene and alkoxy groups. The reaction is initiated through H-abstraction. The product distribution depends upon the substituents on the thiophene ring.
Lewis base, N-methylmorpholine (NMM) accelerated Pd-catalyzed Sonogashira coupling of steric hindered super active esters, la-le, and terminal alkynes. This approach provided an efficient synthetic protocol for a broad array of acylated o-alkynoylphenols compounds, 3a-3e, under moderate conditions. The mechanistic study clearly demonstrated that NNM stabilized the catalytic palladium species, and accelerated the leaving of triazine moiety during the catalytic cycle of the cross-coupling reactions. In addition, piperazine was found to efficiently catalyze the 6-endo cyclization of acylated o-alkynoylphenols, which achieved the diversity oriented synthesis of gamma-benzopyranones, 4aa-4eg, with 93-99% yields. (C) 2016 Elsevier B.V. All rights reserved.
MAZUMDAR, A. K. D.;SAHA, G. C.;SINHA, T. K.;BANERJI, K. D., J. INDIAN CHEM. SOC., 1985, 61, N 11, 996-997
作者:MAZUMDAR, A. K. D.、SAHA, G. C.、SINHA, T. K.、BANERJI, K. D.