A Regioselective Metal-Free Construction of 3-Aroyl Coumarins by Csp2-H Functionalization
摘要:
A successive metal-free TBHP-mediated regioselective C-H functionalization of coumarins toward expedient synthesis of 3-aroyl coumarins is unveiled. The ongoing method conducted through the reaction of either coumarins or coumarin-3-carboxylic acids with aromatic aldehydes. The optimized reaction condition also worked well with benzyl alcohols and styrenes as surrogates for aldehydes, which bear latent carbonyl functionality.
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。
Chiral Tertiary Amine Catalyzed Asymmetric [4 + 2] Cyclization of 3-Aroylcoumarines with 2,3-Butadienoate
commonly found structural units in natural products. Therefore, the introduction of 2H-pyran moiety into the coumarin structural unit, i.e., dihydrocoumarin-fused dihydropyranones, is a potentially successful route for the identification of novel bioactive structures, and the synthesis of these structures has attracted continuing research interest. Herein, a chiraltertiaryamine catalyzed [4 + 2] cyclization