Recent advances of catalytic processes on the transformation of alkynes into functional compounds

Alkynes are important raw materials for the generation of a variety of useful organic compounds through the construction of new C[sbnd]C, C[sbnd]H or C[sbnd]X bonds. Although relatively low in thermodynamic reactivity, alkynes can be readily and selectively activated in the presence of functional groups under mild conditions. The activation is done by means of metal or metal-free catalysis through either selective alkyne C[tbnd]C bond or terminal alkyne C[sbnd]H bond reactions. From the standpoint of green chemistry, it is desirable to develop catalytic processes for the transformation of alkynes that have the least impact on our environment. In this mini-review, we summarize the progresses of alkyne transformation to functional substances in the past six years, with emphasis on the results generated in our research group: heterocoupling of terminal alkynes into unsymmetrical 1,3-diynes, selective hydrogenation of alkynes with formic acid or hypophosphorous acid, and functionalization of alkynes by O-, P-, or S-containing molecules. The advantages and disadvantages of these processes and the effects of reaction conditions are systematically described. Moreover, the catalysts adopted for these processes are illustrated and compared. Finally, we make a prediction on the processes that have potential for industrial applications in the near future.