The first highly enantioselective construction of chiral cyclopropa[c]coumarins was described. Using commercially available (bis)cinchona alkaloid (DHQ)2PYR as the chiral Lewis base catalyst, together with Cs2CO3 as the achiral base, the reaction of a series of coumarin-3-carboxylate and 3-benzoyl coumarins with tert-butyl 2-bromoacetate could give rise to the corresponding cyclopropa[c]coumarins bearing
描述了手性环丙烷[ c ]香豆素的第一个高度对映选择性的结构。使用市售的(bis)金鸡纳生物碱(DHQ)2 PYR作为手性Lewis碱催化剂,以及Cs 2 CO 3作为非手性碱,一系列香豆素3-羧酸盐和3-苯甲酰基香豆素与叔丁基的反应- 2-溴乙酸丁酯可产生相应的带有三个连续手性立体中心的环丙烷[ c ]香豆素,分别在83-93%ee和90-97%ee处。建议该反应通过原位产生的内铵盐中间体进行。
Regioselective transition metal-free acylation of coumarins via cross-dehydrogenative coupling reaction of coumarins and aldehydes
A transition metal-free cross-dehydrogenative coupling reaction is described for the preparation of 3-acylcoumarins. Heating a mixture of a coumarin, an aldehyde, and the K2S2O8/Aliquat 336 system in chlorobenzene at 100 degrees C for 8 h regioselectively afforded the corresponding 3-acylcoumarin derivatives in good to excellent yields. (C) 2016 Elsevier Ltd. All rights reserved.
Iron-catalyzed regioselective direct coupling of aromatic aldehydes with coumarins leading to 3-aroyl coumarins
Iron-catalyzed direct radical acylation of coumarins with aromatic aldehydes to regioselectively afford 3-aroyl coumarin derivatives in moderate yields was described.
N-heterocyclic carbene-catalyzed [4 + 2] cycloaddition of ketenes and 3-aroylcoumarins: highly enantioselective synthesis of dihydrocoumarin-fused dihydropyranones
作者:Teng-Yue Jian、Xiang-Yu Chen、Li-Hui Sun、Song Ye
DOI:10.1039/c2ob26804c
日期:——
The N-heterocyclic carbene-catalyzed [4 + 2] cyclization of ketenes and 3-aroylcoumarins has been developed to give the corresponding dihydrocoumarin-fused multisubstituted dihydropyranones in high yield with good diastereoselectivity and high enantioselectivity.