Hydrogenation of Alkynes and Olefins Catalyzed by Quaternary Ammonium Salts

Abstract

Catalytic hydrogenation of unsaturated hydrocarbons to alkenes and alkanes using molecular hydrogen is one of the most fundamental transformations in organic synthesis. While methodologies involving transition metals as catalysts in homogeneous and heterogeneous processes have been well developed, metal‐free catalytic hydrogenation offers an ideal approach for future chemistry. Herein, the common and inexpensive quaternary ammonium salts are first introduced as catalysts in the catalytic hydrogenation system for the transformations from alkynes or olefins into the corresponding olefins or alkanes. Interestingly, the hydrogenation process of alkynes can be controlled to selectively produce alkenes or alkanes under different conditions. Moreover, the possible mechanism is discussed in new insights into the catalytic behavior of quaternary ammonium salts.

Markovnikov Selective Hydroboration of Aryl Alkenes Catalyzed by Quaternary Ammonium Salts

“…In recent years, quaternary ammonium salts (QASs) have been used as solvents and immobilization media for TM-catalysts but they have garnered significant attention as organocatalysts for the hydrofunctionalization of unsaturated C-C bonds. [32][33][34][35][36][37] We previously reported an ionic liquid-catalyzed anti-Markovnikov selective hydroboration of alkenes (Figure 1b). 38 In the current work, we investigated QASs as catalysts for hydroboration of alkenes leading to Markovnikov organoboranes (Figure 1c).…”