Synthesis of 3‐Methyleneisoindolin‐1‐ones and Isoquinolinium Salts via Exo and Endo Selective Cyclization of 2‐(1‐Alkynyl)benzaldimines. Issue 13 (9th February 2022)

• Record Type: Journal Article
• Authors: Wang, Jiwei; Xie, Congyun; Cheng, Xiang; Liu, Ye; Zhang, Jun
• Is Part Of: Chemistry. Volume 28:Issue 13(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-09
• Subjects: benzocyclobutenes -- exo and endo cyclization -- isoindolinones -- isoquinolinium salts -- terminal alkynes; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202103306
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Coinage metal‐promoted 5‐ exo and 6‐ endo selective cyclization of 2‐(1‐alkynyl)benzaldimines has been studied. It was found that, under gold catalysis, 2‐(1‐alkynyl)benzaldimines exclusively underwent 5‐ exo ‐dig cyclization processes, followed by oxidation to form N ‐aryl 3‐methyleneisoindolin‐1‐ones. In contrast, in the presence of base and under activation of AgOTf, switching of 5‐ exo to 6‐ endo cyclizations of 2‐(1‐alkynyl)benzaldimines was observed, exclusively giving N ‐aryl or N ‐alkyl substituted isoquinolinium salts. The two key reaction intermediates, exocyclic vinyl‐Au and the endocyclic vinyl‐Ag species have been isolated and characterized, and a study of their reactivities confirms the plausible mechanisms. Reactions of the resultant 3‐methyleneisoindolin‐1‐ones with benzyne afforded structurally important isoindolinone‐based benzocyclobutenes. Additionally, several interesting transformations of the resultant isoquinolinium salts have been investigated. Abstract : Gold‐catalyzed 5‐ exo cyclization/oxidation and silver‐promoted 6‐ endo cyclization of 2‐(1‐alkynyl)benzaldimines have been developed to synthesize 3‐methyleneisoindolin‐1‐ones and isoquinolinium salts, respectively. The two kinds of cyclization products could be transformed into isoindolinone‐based benzocyclobutenes, isoquinolinones, 4‐iodo‐isoquinolin‐1(2H)‐one, oxazatricycle, and tetrahydroisoquinoline.