N‐Heterocyclic‐Carbene‐Catalyzed Regioselective Oxidative Ring‐Opening of Epoxides with Aromatic Aldehydes: A Facile Entry to α‐Acyloxyketones

Abstract

Ah igh-yielding synthesis of a-acyloxyketones using aN -heterocyclic-carbene (NHC)-catalyzed, oxidative ring-opening of epoxides with aromatic aldehydes is described. This regioselective,o xidative process utilizes a Nbromosuccinimide( NBS)/DMSO combination as the oxidant system and Et 3 Na st he base under mild reaction conditions. Scheme1.NHC-catalyzed,o xidative ring-opening of epoxides with aromatic aldehydes.[a] R.

Synthesis of α‐Acyloxy‐α′‐hydroxy Ketones via Cyclic Carbonate Intermediates Generated from Tertiary Bromopropargylic Alcohols and Cs2CO3

“…The methods for α‐acyloxy ketone synthesis are α‐acyloxylation of functionalized carbonyl compounds (α‐haloketones, α‐diazoketones) with an alkaline carboxylates or carboxylic acids, the direct oxidative coupling of ketones with carboxylic acids,[7c], oxo‐acyloxylation of the alkenes,[7c], Ru‐catalyzed addition of carboxylic acids to propargylic alcohol. [7c], Also, there have been developed alternative methods: NBS/DBU mediated α‐acyloxylation of benzylic secondary alcohols with carboxylic acids, the transformation of enamides through an intramolecular oxidative acetyl migration process mediated by hydrogen peroxide and acetic anhydride, PhI(OAc) 2 ‐promoted umpolung acetoxylation of enamides, Yb(OTf) 3 ‐catalyzed oxidative decarboxylation of β‐keto acids mediated by (diacetoxyiodo)benzene and carboxylic acids, self‐intermolecular oxidative coupling of aryl ketones using I 2 /TBHP and I 2 /TBHP‐mediated α‐benzoyloxylation of ketones, a HI‐promoted di‐deiodination of α′‐acetoxy‐α,α‐dihaloketones …”

α-Acetoxyarone synthesis via iodine-catalyzed and tert-butyl hydroperoxide-mediateded self-intermolecular oxidative coupling of aryl ketones

“…Recently, robust approaches using organohypervalent iodine reagents and peroxide-mediated oxidative coupling have been developed [ 10 – 11 ]. Although impressive progress has been made [ 12 ], examples of the synthesis of α-acetoxyaryl ketones through self-intermolecular oxidative coupling of aryl ketones are still rare. Yan and coworkers reported the preparation of α-acyloxyaryl ketones from aryl ketones using a Pybox-copper(II) catalyst [ 13 ].…”

N-Heterocyclic Carbene (NHC)/Ag(I) Co-catalyzed Synthesis of 2-Oxo-2-arylethyl Aryl Formates

“…N-溴代丁二酰亚胺(NBS)和 101 kPa O 2 作 为外加氧化剂. 随后, 该课题组借助环氧乙烷的开环, 进一步开发了 NHC 催化芳醛与环氧苯乙烯反应, 合成 了 2-氧代-2-芳乙基芳甲酸酯, 反应中需要 1 equiv.的 NBS 作为外加氧化剂(Scheme 1b) [21] . 2014 年, Forte 等 [22]…”

“…图式 1 NHC 催化下 2-氧代-2-芳乙基芳甲酸酯的合成 Scheme 1 NHC-catalyzed synthesis of 2-oxo-2-arylethyl aryl formates 1 结果与讨论 2-氧代-2-苯乙基-4-氯苯甲酸酯(3a) [21] 191.8, 165.2, 139.8, 134.1, 134.0, 131.4, 128.9, 128.8, 127.8, 66.6;IR (KBr) v: 1724, 1697, 1596, 1275, 1228, 1108, 1090, 1014…”