摘要
利用钯配合物、有机胺和手性布朗斯特酸三元催化剂体系实现了α-取代丙醛参与的1,4-二烯烃的烯丙基碳氢不对称烷基化反应,以良好的产率、优良的区域选择性和立体选择性得到了结构多样的手性α-羰基化合物.此外发现非手性膦配体对钯配合物的催化活性和反应的选择性有十分显著的影响,为后续相关研究提供了新的思路.
In the recent decade, the palladium-catalyzed allylic C—H alkylation reaction of simple alkenes has been well-established as an efficient and atom-economical synthetic alternative for the fine chemical synthesis without the re-quirement of any prefunctionalization, in comparison with the conventional procedures. We recently established a highly enantioselective α-allylation reaction of enolizable aldehydes with terminal alkenes by using a ternary catalyst system, in-cluding palladium, amine, and chiral Bronsted acid, wherein the chiral anion controls the enantioselectivity. Although this protocol provides allylic alkylation products with high levels of enantioselectivity of up to 90% ee, the extension of the opti-mal conditions to a 1,4-diene led to a very low regioslectivity. In the presence of a palladium complex, an oxidant and a chiral phosphoric acid, the 1,4-diene could be smoothly oxidized and principally generated two regiomeric 7c-vinylallyl-palladium phosphate intermediates, either of which led to different products. Therefore, the simultaneous control of regio- and stereose-lectivities in the allylic C—H alkylation reaction of aldehydes with 1,4-dienes would pose additional challenge in comparison with a similar reaction of allylarenes. Herein, we will report an asymmetric a-allylation of enolizable aldehydes with a wide range of 1,4-dienes enabled by cooperative catalysis of a palladium complex, amine, and a chiral Brensted acid. The presence of 6 mol% Pd(OAc)2, 24 mol% P(4-MeOC6H4)3, 6 mol% chiral phosphoric acid (R)-TRIP, 80 mol% cumylamine and 1.50 equivalents of 2,6-dimethylbenzoquinone enabled (E)-penta-l,4-dien-l-ylbenzene (1a) to smoothly undergo the asymmetric allylic C—H alkylation reaction with 2-phenylpropanal (2a), giving rise to the desired a-allylated aldehyde 3a in a 77% iso-lated yield, 11 ; 1 regioselectivity, 20:1 E/Z and 93% ee. Under the optimal conditions, the generality for enolizable alde-hydes was investigated and revealed that 2-aryl propinonaldehydes bearing either ele
作者
周霄乐
苏永亮
汪普生
龚流柱
Zhou Xiao-Le;Su Yong-Liang;Wang Pu-Sheng;Gong Liu-Zhu(School of Chemistry and Materials Science,University of Science and Technology of China,Hefei 230026;Hefei National Laboratory for Physical Sciences at the Mieroscale,Hefei 230026)
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2018年第11期857-861,共5页
Acta Chimica Sinica
基金
国家自然科学基金(Nos.21502183
21602214)资助~~
关键词
不对称催化
钯催化
手性磷酸
1
4-二烯烃
烯丙基碳氢键官能化
asymmetric catalysis
palladium catalysis
chiral phosphoric acid
1,4-diene
allylic C-H functionalization