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

Development of a simple, effective, and practical method for ( Z )-selective semihydrogenation of alkynes has been considered necessary for easy-to-access applications at organic laboratory scales. Herein, ( Z )-selective semihydrogenation of alkynes was achieved using a copper nanocatalyst which was generated in situ simply by adding ammonia borane to an ethanol solution of copper sulfate. Different types of alkynes including aryl-aryl, aryl-alkyl, and aliphatic alkynes were selectively reduced to ( Z )-alkenes affording up to 99% isolated yield. The semihydrogenation of terminal alkynes to alkenes and gram-scale applications were also reported. In addition to eliminating catalyst preparation, the proposed approach is simple and practical and serves as a suitable alternative method to the conventional Lindlar catalyst. A simple and practical method for ( Z )-selective semihydrogenation of alkynes was developed using an in situ generated copper nanocatalyst.