A periodic mesoporous organosilica containing a carbapalladacycle complex as heterogeneous catalyst for Suzuki cross-coupling
摘要:
A series of periodic mesoporous organosilica with varying contents of a carbapalladacycle complex forming part of the walls of the hybrid material has been prepared. These solids have a very large surface area (ca. 1000 m(2) g(-1)), a mononodal pore size distribution (ca. 3 nm), and a periodic hexagonal structure typical for MCM-41 materials. The fresh solids exhibit high activity for the Suzuki cross-coupling of phenylboronic acid with bromobenzoic acid and bromoacetophenone. The initial catalytic activity of these PMO materials is significantly higher than that of a related amorphous silica catalyst containing the same complex. Leaching studies, either filtering the solid in hot solution or three-phase-test attaching one of the reagents to a solid, demonstrate that there is a contribution to the catalysis of leached species from the solid into the solution. The solid can be reused although a progressive deactivation caused by complex degradation, and mesopore collapse has been observed. (C) 2004 Elsevier Inc. All rights reserved.
衍生自苯酮肟1的Palladacycles是有氧条件下在水回流下芳烃硼酸与芳族和杂芳族溴化物和氯化物的Suzuki-Miyaura偶联的有效预催化剂。或者,也可以在室温下在甲醇-水中进行偶联。芳基溴化物使联芳基的TON高达10 5,TOF高达7×10 4 h -1。活化和失活的芳基氯化物需要存在TBAB才能偶联,表现出稍低的效率(TON高达9000,TOF高达3850 h -1)。C(sp 2)C(sp 3)也可以通过三甲基环硼氧烷和丁基硼酸与芳族溴化物和氯化物在水回流下以及苄基和烯丙基氯化物或乙酸酯与芳基硼酸在丙酮-水中在室温下的交叉偶联反应形成。
Nanoparticles (2-10 nm) of palladium have been deposited on single wall carbon nanotubes (SWNT) by spontaneous reduction from Pd(OAc)(2) or from oxime carbapalladacycle. These catalysts exhibit higher catalytic activity than palladium over activated carbon (Pd/C) for the Heck reaction of styrene and iodobenzene and for the Suzuki coupling of phenylboronic and iodobenzene. This fact has been attributed as reflecting the dramatic influence of the size particle on the activity of the palladium catalyst for C-C bond forming reactions as compared to other reaction types less demanding from the point of view of the particle size. Thus, in contrast to the Heck and Suzuki reactions, Pd/C is more active than palladium nanoparticles deposited on SWNT for the catalytic oxidation by molecular oxygen of cinnamyl alcohol to cinnamaldehyde and for the hydrogenation of cinnamaldehyde to 3-phenylpropionaldehyde. (c) 2004 Elsevier B.V. All rights reserved.
A copper- and amine-free sonogashira reaction catalyzed by a supported bis(oxime palladacycle) on magnetized SBA-15
作者:Fatemeh Ghahramani、Yagoub Mansoori、Dolores Esquivel、M. Angeles Navarro