DFT Study On The Mechanisms Of Alkynes Reactions Catalyzed By Gold And Platinum Complexes

In the present paper, the density functional theory (DFT) is employed to study the reaction mechanisms of AuCl3-catalyzed 2-(1-alkynyl)-2-alken-1-ones with nucleo-philes, and PtCl2-catalyzed intramolecular cyclization of o-benzyl arylalkynes, espectively. The effects of catalysts ligands on the mechanism are examined. the reaction mechanism provides these information to design new types of catalysis.1. Study on the Mechanism of AuCl3-Catalyzed Synthesis of Highly Substituted Furans Based on 2-(1-Alkynyl)-2-Alken-l-OnesWe investigate the mechanism of the AuCl3-catalyzed synthesis of highly substituted furans from 2-(1-alkynyl)-2-alken-1-ones with nucleophiles using the density functional theory (DFT), and we obtain the optimal pathway. The rate-determining step of the cyclization is H-migration from the hydroxy group to a ligand Cl of AuCl3 with a 49.3 kJ-mol-1 energy barrier. The calculated results show that the ligand Cl of AuCl3 plays an important role in the reaction, which stabilizes the catalyst and is also directly involved in the reaction. The active energy of proton transfer decreases from 71.5 kJ·mol-1 to 49.3 kJ·mol-1 by assisting the proton transfer. In addition, the reason why HBF4 cannot catalyze the cyclization of 2-(1-alkynyl)-2-alken-l-ones is also discussed in this work. The theoretical results are consistent with the experimental observations.2. Study on the Mechanism of PtCl2-catalyzed intramolecular cyclization of o-benzyl arylalkynesThe mechanism of the PtCl2-catalyzed intramolecular cyclization of o-benzyl arylalkynes is investigated using the density functional theory (DFT), and the optimal pathway is obtained. The catalytic cycle involves the following elementary processes: (1) coordination of o-benzyl arylalkynes to form a p-complex; (2) H-migration; (3) intramolecular cyclization; (4) release of catalysis.The rate-determining step of the cyclization is H-migration from the C5 to C2 with a 101.8 kJ·mol-1 energy barrier. In addition, the reason why the use of CuBr additives increases the yield to 82%, and the use of CuI additives decreases the yield to 10% is also discussed. The theoretical results are consistent with the experimental observations.