Design of coordinatively unsaturated transition metal complexes for controlled radical reactions

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K13996
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Synthetic chemistry
• Research Institution: Kyushu University
• Principal Investigator: Nagashima Hideo 九州大学, 先導物質化学研究所, 教授 (50159076)
• Co-Investigator(Kenkyū-buntansha): 田原 淳士 九州大学, 先導物質化学研究所, 助教 (50713145)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: ラジカル反応 / 不斉合成 / 遷移金属触媒 / 配位不飽和錯体

Outline of Final Research Achievements

Coordinatively unsaturated transition metal complexes were synthesized and subjected to studies on dynamic resolution of secondary alkyl halides and asymmetric addition of bromotrichloromethane to styrene. The hydrophobic effect of water as the solvent was examined to achieve efficient asymmetric induction. Four new Fe complexes derived from 1,4,7-triazacyclononane ligands and chiral diols or a chiral sulfonic acid were synthesized and characterized. These unfortunately did not show good catalytic activity and asymmetric induction. Transition metal complexes were prepared from Rh, Ru, Ir, Fe, Co, or Cu precursors and a chiral bidentate phosphine. Among them, the Rh complexes exhibit excellent catalytic activity and moderate asymmetric induction for the addition reaction of bromotrichloromethane to styrene in both organic solvents and water. In contrast, the Fe complexes showed good catalytic activity only in organic solvents, and no asymmetric induction was observed.

Free Research Field

有機金属化学

Academic Significance and Societal Importance of the Research Achievements

ラジカル反応は有機・高分子合成反応に広範に利用されているが、その反応制御、とくに、高い選択性を持つ反応の実現は困難である。本研究では、ラジカル種の不斉制御を、適切に設計された配位不飽和遷移金属錯体と水の疎水性効果の組み合わせを用いることにより、この困難な課題の解決を図ったものである。成果として、触媒活性と不斉誘起双方を達成するには、触媒の2電子酸化還元機能と水の疎水性効果が有効であること、逆に、1電子酸化還元能力が高い触媒は高い触媒活性を示すが、不斉誘起能力に欠けること、水溶性を示す触媒は疎水性効果を発現しにくい、といった、当該課題の解決に有効な要因を明らかにした。