Ruthenium-NHC-Catalyzed Asymmetric Hydrogenation of Flavones and Chromones: General Access to Enantiomerically Enriched Flavanones, Flavanols, Chromanones, and Chromanols
作者:Dongbing Zhao、Bernhard Beiring、Frank Glorius
DOI:10.1002/anie.201302573
日期:2013.8.5
Two to four! Readily available flavones and chromones were efficiently converted into four valuable chiral classes of O‐heterocycles—flavanones, chromanones, flavanols, and chromanols—by means of an enantioselective Ru/NHC‐catalyzed hydrogenation process (see scheme; NHC=N‐heterocyclic carbene, PCC=pyridinium chlorochromate).
Benzopyrans. Part 41. Reactions of 2-(2-dimethylaminovinyl)-1-benzopyran-4-ones with various dienophiles
作者:Chandra Kanta Ghosh、Samita Bhattacharyya、Chandreyi Ghosh、Amarendra Patra
DOI:10.1039/a903145f
日期:——
propiolate (EP) ultimately gives xanthenones 33, 34 and 37, respectively, the latter being admixed with flavone 43. Enamine 2, cyclisable to xanthenone 11, gives 33 and 35 with DMAD, and 37 and 44 with EP. Reaction of 3 with DMAD affords 36 exclusively.
One-pot synthesis of 3-(furan-2-yl)-4H-chromen-4-ones from 1-(2-hydroxyphenyl)butane-1,3-diones and 2,5-dimethoxy-2,5-dihydrofuran catalyzed via K10 montmorillonite under solvent-free conditions
A new, concise and efficient method of one-potsynthesis of 3-(furan-2-yl)-4H-chromen-4-ones was developed using K10 montmorillonite catalysis undersolvent-freeconditions.
The alkylation and ring-expansion of chromones by diazoalkanes; reluctance of oxygen to engage in sigmatropic shifts
作者:Francis M. Dean、Robert S. Johnson
DOI:10.1039/p19810000224
日期:——
In general, chromones activated by electron-withdrawing groups at position 3 are alkylated (at position 2) by diazoalkanes in the same manner as the isomeric coumarins. For example, 6-methylchromone-3-carbonitrile (3a) is converted by diazoethane into 2-ethyl-6-methylchromone-3-carbonitrile (3c). 2-Diazopropane affords cyclopropane by-products as well, and a 3-formyl group usually suffers homologation
Enantioselective Synthesis of Chromanones through Organocatalytic Tandem Reactions
作者:Mengxue Lu、Xin Wang、Zongli Xiong、Jingxiang Duan、Wen Ren、Weijun Yao、Yi Xia、Zhen Wang
DOI:10.1002/adsc.202001031
日期:2020.12.8
An enantioselective approach to lactone‐fused chromanone derivatives from 1‐(2‐hydroxyaryl)‐1,3‐diketones and α,β‐unsaturated aldehydes under mild conditions has been developed, which included organocatalytic stepwise Michaeladdition/ cycloketalization/hemiacetalization and followed by oxidation reaction. In the presence of chiral amine organocatalyst and an additional salicylic acid, a wide range