Highly active catalyst for the heterogeneous Suzuki-Miyaura reaction: assembled complex of palladium and non-cross-linked amphiphilic polymer.
An assembled insoluble catalyst, PdAS, prepared from palladium ((NH4)2PdCl4 (1)) and non-cross-linked amphiphilic copolymer poly(N-isopropylacrylamide-co-4-diphenylstyrylphosphine) (2) was developed. It was found that PdAS is an excellent catalyst for the Suzuki-Miyaura reaction on three points: (1) The use of 8 x 10(-7) to 5 x 10(-4) mol equiv of PdAS afforded the coupling products efficiently after easy workup, with the turnover number reaching up to 1,250,000. (2) The catalyst was reusable many times without loss of catalytic activity. (3) PdAS showed good stability in any reaction medium (i.e., water or aqueous or anhydrous organic solvents). Analytical study of PdAS indicates that the phosphines in 2 coordinate to palladium to form PdCl2(PPh2Ar)2 species.