Mono-and dinuclear cyclopalladates as catalysts for Suzuki-Miyaura cross-coupling reactions in predominantly aqueous media

Suzuki-Miyaura cross-coupling reactions of aryl halides with arylboronic acids were performed in predominantly aqueous media employing two mono-and two dinuclear cyclopalladated complexes as catalysts. These complexes are [Pd(HL)Cl] (I), [Pd(L)(PPh3)] (II), [Pd-2(y-dppb)(L)(2)] (III) and [Pd-2(mu-dppf)(L)2] (IV); where H2L, dppb and dppf represent 4-methoxy-N'-(mesitylidene)benzohydrazide, 1,4-bis (diphenylphosphino)butane and 1,1'-bis(diphenylphosphino)ferrocene, respectively. The reactions were conducted using potassium carbonate as base in presence of tetrabutylammonium bromide (TBAB) at 70/90 degrees C in dimethylformamide-water (1:20) mixture. Among the four catalysts used, the dinuclear complex IV turned out to be the most effective and afforded moderate to excellent yields with broad substrate scope. (C) 2017 Elsevier Ltd. All rights reserved.