An effective and applicable deuteration method for alkyl-substituted aromatic compounds using a heterogeneous Pd/C and Pt/C mixed catalyst in deuterium oxide in the presence of a small amount of hydrogen gas was developed. Mixing a heterogeneous palladium and platinum catalyst provides an interesting synergistic effect in the H-D exchange reaction and leads to full H-D exchange results even on sterically hindered sites, which indicated only low-deuterium efficiencies when either Pd/C or Pt/C were used independently as a catalyst. We investigated the synergistic effect using a variety of substrates and proved the broad generality of the heterogeneous Pd-Pt-D2O-H2 system in the H-D exchange reaction. Furthermore, this system could be applied to a multigram scale synthesis of useful deuterium-labeled compounds, such as deuterium-labeled bis-aniline derivatives as raw materials for polyimides, aryl iodides as synthetic building blocks, and biologically active compounds.
Specific deuterium isotope effects on the rates of electron transfer within geminate radical-ion pairs
作者:Ian R. Gould、Samir. Farid
DOI:10.1021/ja00231a053
日期:1988.11
The results of the first systematic study of the effect of isotopic substitution on the rates of electron transfer for reactions in the inverted region are reported. Rates of return electron transfer within germinate radical ion pairs of 9,10-dicyanoanthracene (DCA) and 2,6,9,10-tetracyanoanthracene (TCA) radical ions and radical cations of perdeuteriated methyl-substituted benzene derivatives determined
We prepared several activated carbon-supported bimetallic Pd-Pt catalysts (Pd-Pt/C) by using various reducing reagents, and examined their catalytic activities for the deuteration of alkyl-substituted aromatic compounds. Multiple deuterations catalyzed by Pt-Pd/C proceeded in D2O at 180 ËC under a H2 atmosphere, and a synergistic effect was observed in relation to the incorporation of deuterium at sterically hindered positions on aromatic rings.