Catalytic Conversion Of Alkynes Over Polymer-Based Metal Catalysts

Alkynes are one of the most important raw materials in the polymer industry and fine chemical synthesis.Due to the low reactivity of alkyne,super reaction systems should be used in the high-value conversion of alkynes.Catalysts are the most critical factor in the conversion.Three new polymer-based metal catalysts were designed and prepared for the oxidative coupling of alkynes,selective hydrogenation and alkyne-amine-aldehyde?A3?coupling reactions.1.Selective hydrogenation of alkynes.The size-controlled Pd nanoparticles supported on a RAFT polymer gel for the semihydrogenation of alkynes to alkenes.The experimental results show that the size of Pd nanoparticles can be easily adjusted by changing the molar ratio between sulfur and palladium.The trithiocarbonate group in the RAFT can be used not only as a chain transfer agent?CTA?in RATF polymerization,but also as an anchor point and a poisoning agent for Pd nanoparticles.The Pd/SPMB-2.7 with a medium Pd particle size of5.3 nm exhibited excellent activity,stability,and selectivity for alkenes in the semihydrogenation of both internal and terminal alkynes.The results of TEM,SEM,XRD and other characterization revealed that the coverage of S^2-and thiolates on the surface of Pd were responsible for the selectivity improvement of cis-alkenes.2.Oxidative coupling of alkynes.Copper powder/n-butylamine was an effective catalytic system for the oxidative coupling of terminal alkynes to 1,3-diynes,including 13 symmetrical and 14 unsymmetrical.Compared with other Cu-based catalysts and precious metal catalysts,the reaction featured high TOF value(14.7 h^-1 in acetonitrile and 59.4 h^-1under solvent-free condition)Moreover,the Cu active specie was characterized by MALDI-TOF-MS and XPS,and a plausible mechanism for the efficient oxidative coupling of terminal alkynes have been proposed.3.A3 coupling reaction of alkynes.Nitrogen/sulfur co-doped porous carbon?NSC?material was prepared via the carbonization of chitosan and thiourea mixture using salt template method.NSC supported Au nanoparticles prepared by in situ reduction of Au precursor was highly stable in the A3 coupling reaction.Screening of carbonization temperature and content of sulfur provided the best catalyst with high activity.Finally,the effects of porous morphology,sulfur and gold content on the catalytic performance were investigated by TEM,BET and other necessary characterizations.