多機能な分子性触媒を志向したホスホニウムイリドの創製

Abstract

Environmentally-friendly chemical syntheses are desired for creating a sustainable society. In the field of catalysis development, organocatalysts have emerged as green catalysts and great progress in their use has been made over the past two decades. Phosphonium ylides-the cationic site is composed of a phosphonium ion and the negatively charged atom directly attached to the phosphorus center-are a specific type of zwitterion as well as phosphorus(V) compounds. Taking account of the nucleophilicity of the anionic carbon, versatile transformations have been accomplished. Despite being attractive chemical species, however, their catalytic ability has remained elusive and there are no reports on phosphonium ylide catalysts that enable multiple transformations. Hence the development of phosphonium ylide catalysis is of formidable challenge and can open a new frontier for the field of ylide chemistry. Our group focused on carbonyl-stabilized phosphonium ylides, which are synthesized from bifunctional tetraarylphosphonium salts, and has been exploring their catalytic functions as multifunctional organocatalysts. We herein describe the design of novel phosphonium ylide catalysts and the reactions using phosphonium ylides as a nucleophilic catalyst, photoredox catalyst, and Lewis base catalyst. Bifunctional tetraarylphosphonium salts-catalyzed [3+2] reactions between epoxides and heteroallenes such as carbon dioxide and isocyanates are also reported.