A straightforward catalytic approach to obtain deuterated chloroform at room temperature

Abstract

We report the catalytic activity for the complexes-cis-[RuCl₂ (dppb)(bipy)] (A), and [η⁶ -(p-cymene)Ru (dppb)Cl]PF₆ (B), wherein dppb = 1,4-bis(diphenylphosphine)butane, and bipy = 2,2'-bipyridine-for the synthesis of CDCl₃ from CHCl₃ using D₂ O as deuterium source. H/D exchange reactions were performed using a chloroform/D₂ O, 1:2 molar ratio, vigorously stirred, at room temperature. One mole of KOH was dissolved in D₂ O fraction and catalytic complexes from 0.002 to 0.05 mmol were dissolved in chloroform. The H/D exchange reactions were monitored using ¹³ C nuclear magnetic resonance sequences without proton decoupling. The reaction using 0.01 mmol of compound A reached approximately 55% of H/D conversion in 1 h. In the same time, the reactions with 0.002 mmol of compound A and without catalyst show approximately 28% and 3% H/D exchange, respectively. Without the catalysts, the H/D exchange was only 12.0% in 5 h. For compound B, 55% H/D conversion was observed in 1 h, only when 0.05 mmol was used, which is much higher catalyst concentration. After the isolation of the chloroform fraction and two more addition of D₂ O, it was possible to obtain 95.0% H/D exchange in approximately 3 h, using 0.01 mmol of the compound A. Therefore, compound A is an efficient catalyst for a rapid and straightforward synthesis of CDCl₃ from CHCl₃ at room temperature and using D₂ O as deuterium source.

Keywords: H/D exchange; NMR spectroscopy; catalysis; deuterated chloroform; ruthenium complexes.