Current Organic Chemistry - Volume 20, Issue 4, 2016

Palladium catalysts supported on different inorganic materials have been reported to catalyze C-C bond formation reactions and extensive review articles are available in the literature considering this issue. However, in order to increase the capacity of the supports to bind palladium as the active catalyst, the surface of a large number of solids has been modified with organic moieties. The negative aspects of these modifications are that they are time-consuming and sometimes tedious procedures. In addition, they increase the cost of the reactions which is not desirable in economic point of view. On the other hand, naturally occurring organic solids which are inexpensive, available and abundant in nature are good alternative to inorganic supports despite their relatively lower thermal stabilities. The surface of these solids fully covered by chelating groups and often the surface modifications are not needed. In a recent perspective article, the application of palladium supported on polysaccharides in coupling reactions has been reviewed by Molnar and Papp. In the present review, we have focused our attention to the endeavors utilizing palladium particles supported on natural organic solids for the construction of C-C bonds by Mizoroki-Heck, Sonogashira- Hagihara, Suzuki-Miyaura and homocoupling reactions which are the most important palladium-catalyzed reactions.

Over the past few years, the use of heterogeneous catalytic systems has been preferred to homogeneous counterparts because of their practical benefits such as convenient separation from the reaction mixture and reusability of the catalysts in successive reaction runs which could improve the environmental, economic and sustainability factors of organic reactions. Thus, attempts have been directed to develop varied solid catalyst supports to improve the efficiency and recovering ability of the prepared catalysts while minimizing the deterrent effect of the bulky supports in catalyst activity. Among this, ordered mesoporous silica materials have attracted considerable interest owing to their noteworthy and desirable properties for catalytic applications such as high specific surface area, accessible pore volume, tunable pore size and easy functionalization. Because of the great significance of C-C coupling reactions, the main goal of this review is specifically focusing on the application of supported metal catalysts on both ordered mesoporous silica (OMS) and periodic mesoporous organosilica (PMO) in C-C couplings.

The focus of this review is on recent advancements in C–H activation having been reported in the last 2– 3 years. Both light-induced methods with the use of ruthenium photoredox catalysts and Ru-catalyzed processes accomplished through C–H activation are treated. Various C–C bond forming reactions—among others, alkylation and alkenylation of arenes, biaryl synthesis, annulations with multiple couplings as well as C–heteroatom couplings— are treated in subsections. Particular emphasis is given to the role of directing groups and related selectivity issues (regio-, chemo- and site-selectivity). Mechanistic issues are briefly highlighted to show key intermediates thereby shedding light on product forming process. This review may serve as a useful reference for chemists interested in recent developments of these rapidly developing fields by providing a selection from the plethora of new, invaluable information.

Molecularly imprinted polymers (MIPs) are synthetic materials with tailor-made binding sites for a variety of chemical substances. However, the optimization of MIPs formulation is time-consuming and labourintensive since the interactions presenting in the pre-polymerisation mixture are complicated. Therefore, chemometrics, in which mathematical or statistical methods are used to analyze data, has been regarded as a useful tool to the optimization of MIP preparation. This article gave a mini review of the current status of the synthetic strategies in MIPs based on chemometric and computational methods in the past decade. The perspectives in the computation-based optimization for MIP preparation were also discussed.