N-Heterocyclic Carbene/Potassium Ion Cooperatively Catalyzed Phenylation Reactions of α,β-Unsaturated Acylazoliums

• Published in: European journal of organic chemistry Vol. 2016; no. 26; pp. 4569 - 4576
• Main Authors: Zheng, Jinhua, Zhu, Kejie, Yuan, Yaofeng, Cheng, Jiajia
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.09.2016
• Subjects: Carbenes; Cyclization; Nitrogen heterocycles; Organocatalysis; Oxygen heterocycles; Potassium
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201600838

A catalytic phenylation reaction of α,β‐unsaturated acylazoliums with in‐situ‐generated phenolates was developed. A combination of N‐heterocyclic carbene and potassium ion cooperatively catalyzed the generation of α,β‐unsaturated acylazoliums and phenolates from α,β‐unsaturated phenolic esters for the efficient [3+3] annulation, which involves a dearomatization–rearomatization process. The approach gives good yields and excellent regioselectivities, and the products could be easily converted into high‐value polycyclic derivatives. Mechanistic studies demonstrated that the potassium ion plays a vital role in this reaction. A catalytic phenylation reaction of α,β‐unsaturated acylazoliums was developed. A combination of N‐heterocyclic carbene and potassium ion cooperatively catalyzed the cyclization of α,β‐unsaturated acylazoliums with phenolates, which are directly generated from α,β‐unsaturated phenolic esters. Mechanistic studies demonstrated that the potassium ion plays a vital role in this reaction.