Hydroxycarbonylation of alkenes with formic acid using a rhodium iodide complex and alkyl ammonium iodide

Hydroxycarbonylation of alkenes using formic acid (HCOOH) is ideal for the synthesis of various carboxylic acids as a means to develop a sustainable reaction system with lower environmental impact. In this study, we developed a new catalytic system for hydroxycarbonylation of alkenes with HCOOH using a Vaska-type Rh complex with an iodide ligand, RhI(CO)(PPh3)(2) (1), as the catalyst, and a quaternary ammonium iodide salt as the promoter for the catalyst. In comparison with similar reaction systems using Rh catalysts, our reaction system is safer and more environmentally friendly since it does not require high-pressure conditions, explosive gases, or environmentally unfriendly CH3I and extra PPh3 promoters. In addition, we also experimentally clarified that the catalytic reaction proceeds via RhHI2(CO)(PPh3)(2) (2), which is formed by the reaction of 1 with a quaternary ammonium iodide salt and p-TsOH. Furthermore, the Rh(iii) complex 2 can catalyze hydroxycarbonylation of alkenes with HCOOH without any promoters.

Automated summary

A new catalytic system for hydroxycarbonylation of alkenes using a Vaska-type Rh complex and a quaternary ammonium iodide salt as a promoter was developed in this study. The reaction system is safer and more environmentally friendly compared to similar systems using Rh catalysts, as it does not require high-pressure conditions, explosive gases, or environmentally unfriendly promoters. Additionally, it was experimentally confirmed that the catalytic reaction proceeds via a Rh(iii) complex without any promoters.