Metal-free organic reactions

In the following, AIMD studies of the 8 2 reaction shall be briefly reviewed. Other metal-free organic reactions like the Diels-Alder and the Wittig reactimi have been... 

The molecular weight (M , GPO with polystyrene standard) is in the range of 8-14 kD (P 10-30). The M values for the metal-organic polymers are generally lower compared to that of the metal-free organic polymer (Pq). The authors therefore came to the conclusion that the Re-bipyridine monomer 58 is less reactive in the Pd-catalyzed cross-coupling reaction compared to the biphenyl monomer 59. These polymers have also been characterized by and NMR, as well as by FTIR spectroscopy. 

Recently, direct catalytic asymmetric Mannich-type reactions were reported via C-H activation of carbonyl compounds. The transformations are catalyzed both by organometallic complexes and metal-free organic catalysts. 

The solvomercuration of alkenes has an important synthetic valne since it allows the asymmetric functionalization of olefins. Although a large number of organomercurials have been isolated from these reactions, more commonly, they are reduced with alkaline NaBELi to yield the corresponding metal-free organic species (see Section 4.1). In this way, olefins can be converted into a wide range of organic species such as alcohols, ethers, and amines. 

Organocatalysis is basically the reactions require an organic-based metal free catalyst in order to accelerate chemical reactions, and provide operational simplicity and low toxicity [1-3]. Owing to the metal free organic compotmds contaminant, organocatalysts attracted much attention in many fields of green chemistry associating food, pharmaceutical, and cosmetic industries [4]. 

The influence of pressure on organic reactions catalyzed by chiral metal-free organic molecules was studied for selected asymmetric Michael, Baylis-Hillman, aldol, Mannich, Friedel-Crafls, and Diels-Alder reactions-the essential part of this work was done in Japan. In the early stages of those investigations the high-pressure technique was applied to reactions catalyzed by cinchona alkaloids and in most cases low or moderate enantioselectivities were observed. Since 2002 some examples of high-pressure reactions catalyzed by proUne, thioureas, and modified cinchona alkaloids have appeared. 

Most of the free-radical mechanisms discussed thus far have involved some combination of homolytic bond dissociation, atom abstraction, and addition steps. In this section, we will discuss reactions that include discrete electron-transfer steps. Addition to or removal of one electron fi om a diamagnetic organic molecule generates a radical. Organic reactions that involve electron-transfer steps are often mediated by transition-metal ions. Many transition-metal ions have two or more relatively stable oxidation states differing by one electron. Transition-metal ions therefore firequently participate in electron-transfer processes. 

Transformations to polymer-bound amino compounds, which are often useful as ligands for metals ions or other free species (67), employ a wide selection of organic reactions. Quaternary ammonium salts result from heating isolated polymer tosylate with tertiary amine they may also be prepared in one step from (hydroxyethyl)polystyrene and toluenesulfonyl chloride and a two-fold excess of amine. 

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