- Volume 1, Issue 1, 2005

The art of carrying out efficient chemical transformations is a major concern in modern organic synthesis. Two aspects are of utmost importance when considering the outcome of a reaction, selectivity and efficiency (optimization of yields). The right activation mode is, therefore, determining. In this book, activation should be understood in a rather wide sense. Activation is here described as a sort of catalysis facilitating the cou Read More

Light is a powerful activator for many standard and non-standard organic transformations. This review focuses on the photochemical activation of organic reactions that can also occur thermally, in particular isomerization, acylation, hydrolysis, ionization, enolization and aromatic substitutions. Asymmetric reactions with polarized light will also be briefly discussed.

High pressure activation is presented as a potent synthetic strategy depending on the magnitude of the activation volume. Coupling of high pressure with ancillary activation methods such as catalysis widens the methodology. The application fields are reviewed: Diels-Alder reactions, 1,3- dipolar cycloadditions, [2+2] cycloadditions, Michael and related reactions, Baylis-Hillman additions etc... Many valuable substances can Read More

In the present chapter an overview about various ultrasoundassisted reactions are given. Based on fundamental physical principles modern trends in various reaction types are discussed. Especially typical aspects for scaling up ultrasound-assisted reactions are presented.

Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur by conventional heating and even modifications of selectivity (chemo-, regioand stereoselectivity). An overview of the application of micro Read More

The Lewis acids derived from Ga, In, Sb and Bi were slowly replacing “traditional” Lewis acids. The reaction conditions using such Lewis acids are usually mild and compatible with much functionality. In addition, these Lewis acids frequently show unique chemistry, which foster niche applications and prompt further research into their chemistry.

Perchlorates have been frequently employed to promote a variety of synthetic transformations under ambient conditions. For example, the LiClO4-diethyl ether solvent medium has proven to be a powerful substitute for external high pressure for Diels-Alder reactions and other organic reactions. In this chapter are discussed several such organic transformations where perchlorates have played highly significant role in p Read More

The immobilization of homogeneous catalysts on supports is used to facilitate the catalyst separation from reaction mixtures and their recycling. In addition to this practical merit, some reports have demonstrated that the immobilization of a catalyst can also positively influence catalytic performance (increase in catalytic activity, stability and selectivity). In this chapter, the positive effects of immobilization on catalytic effi Read More

Catalysis plays a vital role in chemical transformation. The discovery of the Wilkinson catalyst, Rh(Ph3P)3Cl, for hydrogenation stimulated a lot of attempts to develop the enantioselective version of these reactions by using optically active transition metal complexes [1]. In the beginning, only very low enantioselectivity was obtained in the hydrogenation of 2-phenylacrylic acid and 2-phenyl-1-propene with certain chiral tertiary Read More

Supramolecular catalysis by cyclodextrins involving non-covalent inter molecular forces and host-guest complexation has been shown to result in high selectivities in a variety of organic reactions by the cyclodextrin molecular recognition ability and effective use of their hydroxyl groups and derivatives. Some of the applications of cyclodextrins discussed are: enzyme models, enzyme catalysed reactions, regioselective ring op Read More

Review of organic reactions in which solvophobic effects could be implied in the activation process is presented with a particular emphasis on reactions performed in water.

Reactive intermediates such as carbocations, carbanions, radicals and radical ions can be electrochemically generated from various electroactive species. Those intermediates may react chemically (C) or electrochemically (E) according to EC, ECE mechanisms. Anodic oxidations produce acidic or electrophilic species, which can react with nucleophiles or (and) eliminate protons or electrophiles. Cathodic reductions afford basic o Read More

Biocatalytic reactions using enzymes or whole microbial cells are increasingly employed for organic synthesis, taking advantage of their high versatility and exquisite selectivities (chemo-, regio- and stereoselectivity). Resolution of racemates and its refinements, desymmetrisation of meso- and prochiral compounds by oxidoreduction, some C-C bond forming reactions and other miscellaneous reactions will be outlined, illustr Read More

In this chapter, we describe some of the general strategies implemented by the experimenter to challenge the immune system for the production of antibodies that act as catalysts. Some representative strategies include the use of haptens that are transition state analogues, the “bait and switch” strategy and the concept of “reactive immunisation”. These protocols have allowed the preparation of catalytic antibodies for va Read More