61883-37-2Relevant academic research and scientific papers
Ligand-Controlled Regiodivergent Hydrosilylation of Conjugated Dienes Catalyzed by Mono(phosphine)palladium(0) Complexes
Komine, Nobuyuki,Mitsui, Tatsuo,Kikuchi, Shu,Hirano, Masafumi
, p. 4510 - 4524 (2020)
Mono(phosphine)palladium(0) complexes, [Pd(2:2-C6H10O)(PR3)] (1), catalyze hydrosilylation of electron-deficient conjugated dienes with HSiPh3. Hydrosilylation of methyl penta-2,4-dienoate with HSiPh3 catalyzed by [Pd(2:2-C6H10O)(PR3)] (R = Me (1a), Et (1b), OEt (1d), OiPr (1e)) proceeds to give the 1,2-E product in quantitative yield with exclusive Markovnikov selectivity. In contrast, their triphenylphosphine and -phosphite analogues, [Pd(2:2-C6H10O)(PR3)] (R = Ph (1f), OPh (1g)), mainly produce the 1,4-Z product (1,2-E/1,4-Z = 3/7). The regioselectivity in the hydrosilylation of methyl 2,4-pentadienoate is also controlled by organosilanes. Mechanistic studies suggest that the reaction using a compact and basic mono-phosphorus complex proceeds by the Chalk-Harrod mechanism involving the reductive elimination from an (3-allyl)(silyl)palladium(II). A poor electron-donating mono-phosphorus ligand such as P(OPh)3 destabilizes a Pd(II) species and promotes direct reductive elimination to give the 1,4-Z product. On the other hand, a compact and electron-donating phosphorus ligand, such as PMe3, PEt3, and P(OMe)3, favors to give the more stable (3-allyl)(silyl)palladium(II) intermediate by the allyl rotation, followed by reductive elimination to give the 1,2-E product.
