Application of the tandem thionium/N-acyliminium ion cascade toward heterocyclic synthesis

Abstract

Compostos heterocíclicos estruturalmente diversos podem ser facilmente obitdos através do processo sequencial Pummerer/cicloadição/ ciclização via ion N-acilimínio.Many structurally diverse heterocyclic compounds can be easily accessed via the domino Pummerer/cycloaddition/N-acyliminium ion cyclization cascade.

Synthesis of Functionalized Isoindolinones via Calcium Catalyzed Generation and Trapping of N-Acyliminium Ions

“…Traditionally, N -acyliminium ions are generated via the activation and release of a suitable leaving group under acidic conditions. There is a wide range of these suitable leaving groups including hydroxyl, alkyl- and aryloxy, acetoxy, , and carbamate; , however, sulfur containing and sulfoxide based groups have also found use . As the synthetic utility of these intermediates becomes more obvious, the need to generate them using more functionally tolerant reagents remains high.…”

“…There is a wide range of these suitable leaving groups including hydroxyl, 10 alkyl-and aryloxy, 11 acetoxy, 12,13 and carbamate; 14,15 however, sulfur containing and sulfoxide based groups have also found use. 16 As the synthetic utility of these intermediates becomes more obvious, the need to generate them using more functionally tolerant reagents remains high. Successes using stoichiometric Lewis acids such as BF 3 •OEt 2 , 17 Sc(OTf) 3 , 18 TiCl 4 , 19 and AlCl 3 20 have all recently been reported.…”