A simple and efficient in situ generated copper nanocatalyst for stereoselective semihydrogenation of alkynes

Abstract

Development of a simple, effective, and practical method for (Z)-selective semihydrogenation of alkynes have been considered necessary for easy-to-access applications in organic laboratory scales. Herein, (Z)-selective semihydrogenation of alkynes was...

Stereoselective Semi‐Hydrogenations of Alkynes by First‐Row (3d) Transition Metal Catalysts

“…In contrast to its neighbor in the periodic table, Cu catalysts have only recently been discovered as semi‐hydrogenation catalysts with good levels of activity and stereocontrol under mild conditions. Examples include the use of copper nanoparticles generated by reduction of CuSO 4 using NaBH 4 by Moran and co‐workers, [119] bearing close resemblance to P‐2 Ni. The complete absence of dihydrogen or sophisticated hydrogen sources makes this protocol, employing available ethylene glycol as the H 2 source, easily accessible and sustainable.…”

Copper-Catalyzed Diboron-Mediated cis-Semi-Hydrogenation of Alkynes under Facile Conditions

“…Nevertheless, the existing Lindlar-type reactions inevitably use high-pressure hydrogen as the hydrogen source, which poses a number of limitations to the reaction, such as potential explosion hazards, cumbersome operations for the use of high-pressure hydrogen, possible over-hydrogenation, and isomerization side reactions. In order to tackle these shortcomings, synthetic scientists developed the transfer hydrogenation reactions, [ 38 , 39 ] which use stable and easily handled reducing agents such as silanes [ 40 , 41 ], formic acid [ 42 ], alcohols [ 43 , 44 ], ammonia borane [ 45 , 46 ], DMF [ 47 ], hypophosphoric acid [ 48 , 49 ], and amines [ 50 ] as indirect hydrogen sources ( Figure 2 b), avoiding the use of flammable hydrogen gas.…”

Palladium-catalyzed transfer hydrogenation of terminal alkynes using ethanol as the hydrogen donor

“…9–11 However, to achieve the transfer hydrogenation reaction and to obtain good product yields, these methods often require the use of explosive, flammable, expensive, or corrosive hydrogenating agents, such as ammonia borane, hydrogen, triethylsilane, and formic acid. 12–18 Therefore, it is necessary to find an economical and safe hydrogen donor for the semi-hydrogenation of alkynes to alkenes. In recent years, ethanol has attracted attention as a safer and more economical hydrogen donor, and more reactions have been reported for the semi-hydrogenation of alkynes to alkenes using ethanol as the hydrogen source.…”