95852-03-2Relevant academic research and scientific papers
Kinetics and Mechanism of Vinylation of ortho-Palladated NN-Dialkylbenzylamines by para-Substituted Styrenes
Ryabov, Alexander D.,Sakodinskaya, Inna K.,Yatsimirsky, Anatoly K.
, p. 1511 - 1518 (1983)
The kinetics of vinylation of ortho-palladated NN-dialkylbenzylamines (1a-g) by CH2=CHC6H4R3-p (R3=H,Cl, Br, Me, and MeO) to form the respective 2-dialkylaminomethylstilbenes (2) has been studied mainly at 30 deg C in acetic acid solvent.The reaction follows second-order kinetics: d/dt=k2.The rate constants k2 increase markedly in the presence of both alkali-metal perchlorates (MClO4) and small concentrations of perchloric acid, k2 being directly proportional to .It is shown that the salt effect originates from the solvolytic reaction MClO4 + HOAc MOAc + HClO4.Conversion of dimer (1a) into the respective monomer (3) stops the reaction, but the latter species readily forms ?-complexes with styrenes.The stability constants of 1:1 ?-complexes have been determined and their Hammett correlation with a slope of -1.87 is established.For a series of substituted styrenes lgk2 is the linear function of Hammett ?p values with a slope of ca. -1.For a series of ring-substituted complexes (1) lgk2 correlates with the pKa of the parent benzylamines with a slope of 0.98.The results are interpreted in terms of a mechanism involving intermediate protonation of (1), ?-co-ordination of alkene, and subsequent rate-determining intramolecular insertion of styrene into a Pd-C bond through a four-centred transition state.
