Chemistry of Frustrated Radical Pairs

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K21189
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 33:Organic chemistry and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Takaya Jun 東京工業大学, 理学院, 准教授 (60401535)
• Project Period (FY): 2020-07-30 – 2023-03-31
• Keywords: 有機合成化学

Outline of Final Research Achievements

An unprecedented photo-promoted skeletal rearrangement reaction of phosphine-borane frustrated Lewis pairs, o-(borylaryl)phosphines, involving cleavage of an unstrained sp2C-sp3C σ-bond is discovered. The reaction realizes an efficient synthesis of cyclic phosphonium-borate compounds. The reaction mechanism via a frustrated radical pair intermediate is proposed based on theoretical calculations. Furthermore, it was also found that o-anisyldimesitylborane underwent skeletal rearrangement under photoirradiation conditions to give (2-benzyl-4,6-dimethylphenyl)mesitylborinic acid after hydrolysis. Experimental studies and theoretical calculations supported that the reaction proceeded via a triplet excited state to form a spiro boracycle intermediate through C-H abstraction and radical coupling. This work sheds light on the new photoreactivity of FLPs.

Free Research Field

有機合成化学

Academic Significance and Societal Importance of the Research Achievements

フラストレイテッドラジカルペアという新しい反応活性種の発生法を確立し，その不活性結合変換反応における有用性を実証した本研究は，基礎有機化学，有機合成化学，機能性分子開発の各分野に新しい研究対象と分子ツールを提供したものとして大きな意義を持つ。