Rh(II)-Cp∗–TsDPEN catalyzed aqueous asymmetric transfer hydrogenation of chromenones into saturated alcohol: CC and CO reduction in one step
摘要:
As an efficient catalyst for asymmetric transfer hydrogenation reaction (ATH reaction) of alpha,beta-unsaturated ketones, Rh-Cp*-TsDPEN (Cp* = 1,2,3,4,5-pentamethylcyclopenta-1,3-diene, TsDPEN = N-(p-toluenesulfonyl)-1,2-diphenyl- ethylenediamine) shows high chemoselectivity on C=O and C=C reduction. In our method, both C=O and C=C bonds in a variety of chromenone derivatives were reduced efficiently in aqueous media, resulting in at least 98% ee and up to 99% yields in a convenient way without further purification. The product was a useful intermediate for deriving chiral chroman-4-amine, which was reported as an effective agent against hypotension and inflammatory pain by inhibiting human bradykinin B1 receptor. (C) 2012 Published by Elsevier Ltd.
Metal-free oxidative decarbonylative alkylation of chromones using aliphatic aldehydes
作者:Rongzhen Chen、Jin-Tao Yu、Jiang Cheng
DOI:10.1039/c8ob00720a
日期:——
A decarbonylative alkylation of chromones via radical conjugate addition under metal-free conditions was developed using aliphaticaldehydes as alkylating reagents. A series of 2-tertiary, secondary, and even primary alkylated chromanones were obtained in moderate to excellent yields.
efficient route for the coupling of maleimides with chromones at the C5-position has been developed under Ru(II) catalysis. It could provide 1,4-addition products and oxidative Heck-type products by switching additives. Benzoic acid led to the formation of 1,4-addition products under solvent-free conditions, and silver acetate was promoted to the generation of oxidative Heck-type products. Various maleimides
NHC-catalyzed enantioselective C2-functionalization of 3-hydroxychromenones <i>via</i> α,β-unsaturated acyl azoliums
作者:Krzysztof Dzieszkowski、Michał Słotwiński、Katarzyna Rafińska、Tadeusz M. Muzioł、Zbigniew Rafiński
DOI:10.1039/d1cc03708k
日期:——
A novel synthetic method for enantioselective C2-functionalization of 3-hydroxychromenones promoted by N-heterocyclic carbenes via the formation of α,β-unsaturatedacylazolium intermediates, which occurs with Coates–Claisen rearrangement is established. This synthetic strategy enabled the rapid assembly of enantiomerically enriched δ-hydroxychromenone-derived esters/amides under mild conditions with
DTBP-promoted site-selective α-alkoxyl C–H functionalization of alkyl esters: synthesis of 2-alkyl ester substituted chromanones
作者:Jin-Tao Yu、Yiting Li、Rongzhen Chen、Zixian Yang、Changduo Pan
DOI:10.1039/d1ob00605c
日期:——
The direct C–H functionalization of ethylacetates was developed, delivering a variety of 1-(4-oxochroman-2-yl)ethylacetate derivatives by reacting with chromones. This reaction has a wide substrate scope with excellent site-selective C–H activation at the inactive α-hydrogen of the alkoxyl group instead of the α-hydrogen of the carbonyl group under radical conditions. Compared with other protocols
A metal-free site-specific C2-hydroxyalkylation of chromones through the Minisci-type reaction using simple alcohols was developed. This transformation proceeds via radical sp3 C–H activation and subsequent conjugateaddition, generating a series of C2-hydroxyalkylated chromanones in moderate to good yields. Besides, ethers were also compatible in this Minisci reaction, leading to corresponding C2