General alkoxylation reactions

Ethylenediamine Alkoxylates. The reaction 1,2-alkylene oxides with ethylenediamine forms the basis of a series of surfactants of the following general stmcture ... 

The preparation described here is a modification of previously used alkoxyl interchange reactions, but it is more convenient because the use of the azeotrope-forming solvent permits the virtually complete removal of the by-product alcohol under mild conditions. The method is general for most primary and sec-... 

The Suzuki coupling was developed by Professor Akira Suzuki of Hokkaido University. The Suzuki coupling uses a boron compound (R-BYj) and an alkenyl, aryl, or alkynyl halide or triflate (RX) as the carbon sources, with a palladium salt as the catalyst. Bromides and iodides are the most commonly used halides chlorides are less reactive. Alkyl halides can sometimes be used but are subject to elimination. A base is also required. The boron compound can be a borane (R jB), a borate ester (R B(OR)2), or a boric acid (R B(OH)2), where R is alkyl, alkenyl, or aryl. The general reaction is shown in the following scheme, where X is halide or triflate and Y is alkyl, alkoxyl, or OH. A list of the types of components that can be used is given in Table 24.1. This reaction is one of the principal methods now used to prepare biaryls. 

Among the most useful radical fragmentation reactions from a synthetic point of view are decarboxylations and fragmentations of alkoxyl radicals. The use of (V-hydroxy-2-thiopyridine esters for decarboxylation is quite general. Several procedures and reagents are available for preparation of the esters,353 and the reaction conditions are compatible with many functional groups.354 f-Butyl mercaptan and thiophenol can serve as hydrogen atom donors. 

Alkoxyl species form very readily from the reaction of alkyl halides on alkali, alkaline earth, transition metal, and lanthanide exchanged zeolites (128, 129). The more basic the zeolite, the more readily the reaction proceeds. Alkyl halides have been used to generate methoxyl, ethoxyl, isopro-poxyl, and ferf-butoxyl species on metal-exchanged zeolites. The mechanistic significance of alkoxyl species in zeolite acid catalysis is not in general clear in some reactions they may be true intermediates, and in others mere spectators. 

The generally accepted mechanism for anodic amide alkoxylation involves the formation and further reaction of an intermediate acylimmonium ion with a nucleophile. The oxidation of Af-methyl-2-hydroxyethylcarbamate was utilized in the synthesis of a 1,3-oxazolidine derivative in 60% yield.117... 

Examples for frequently encountered intermediates in organic reactions are carbocations (carbenium ions, carbonium ions), carbanions, C-centered radicals, carbenes, O-centered radicals (hydroxyl, alkoxyl, peroxyl, superoxide anion radical etc.), nitrenes, N-centered radicals (aminium, iminium), arynes, to name but a few. Generally, with the exception of so-called persistent radicals which are stabilized by special steric or resonance effects, most radicals belong to the class of reactive intermediates. 

Olefin metathesis is a useful tool for the formation of unsaturated C-C bonds in organic synthesis, and the reaction has been generally accepted to proceed through a series of metallacyclobutanes and carbene complexe intermediates [40-43]. For this type of reaction, the most widely used catalysts include an alkoxyl imido molybdenum complex (Schrock catalyst) [44] and a benzylidene ruthenium complex (Grubbs catalyst) [43]. The former is air- and moisture-sensitive and has some other drawbacks such as intolerance to many functional groups and impurities the latter has increased tolerance to water and many reactions have been used in aqueous solution without any loss of catalytic efficiency. 

A survey of the chlotomethylation of aromatic compounds has been made, and a thorough study of the conditions of the reaction for the production of benzyl chloride has been carried out. The reaction is generally applicable to aromatic hydrocarbons. The effect of substituents on the ease of chloromethylation is pronounced alkyl and alkoxyl groups facilitate the introduction of the chloromethyl group, whereas halogen, Carboxyl, and nitro substituents retard or prevent the reaction. Zinc chloride, sulfuric acid, and phosphoric acid have been used as catalysts when needed. A chief by-product is the f is -chloromethyl compound. 

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