Help bases triethylamine

In the presence of CTAB, the coupling reactions of electron-rich and -deficient aromatic bromides or iodides with olefins, such as acrylate, acrylonitrile, or styrene, proceeded in water at 80-130°C to give 80-95% yields of the desired products. Selected examples are given in Scheme 6.33. In situ generated Pd nanoparticles are likely to be the active catalyst. Apart from acting as a base, triethylamine could help generate active catalyst species in water [143]. 

The simplest and most generally useful synthetic method for metal diketonates is from the diketone and a metal such as a halide, hydroxide, oxide, sulfate, carbonate, carboxylate, etc. in a variety of solvents such as water, alcohol, carbon tetrachloride or neat diketone. Since many / -diketones are poorly soluble in water, use of an organic solvent or cosolvent may be helpful. Optionally, a base such as sodium carbonate, triethylamine or urea may be added. Addition of a base early in the reaction converts the diketone to its conjugate base, which usually has greater solubility in aqueous media.159 In some cases, metal halide complexes of the diketone form as intermediates, e.g. SnCl4(MeCOCH2COMe), which has been formulated as... 

In most cases, the halide is a bromide or an iodide, and the alkene is typically mono-substituted. The palladium catalyst might be Pd(OAc)2 or PdCl2 or a variety of other palladium compounds. Only a small amount of the expensive palladium catalyst is needed. A base such as triethylamine or sodium acetate is added to neutralize the HX released in the reaction. Many reactions use triphenylphosphine (PPh3) to complex with the palladium, which helps stabilize it and enhances its reactivity. 

Oxa-thiacrown ethers containing oxadiazole units 87-92 were prepared from l,4-bis(5-mercapto-l,3,4-oxadiazol-2-yl)butane and various l,tu-dihaloalkanes in the presence of KOH (Scheme 13) <2003HAC273>. When organic bases, such as triethylamine or pyridine, were employed, the cyclic products were not obtained therefore, K+ ions would help in the cyclization. 

One of tlie most common tnethiKl of alcohol protection is roacfion with chlorotrimethylsiUnc to yield a tnmctbylailyl (TNIS> ether. The reaction s carried out in the presonce of a base 1 usually triethylamine) to help lom the alkoxide anion from the alcohol and. to remove the HCI by product fr i the reaction. 

One of the more common methods of alcohol protection is by reaction with a chlorotrialkylsilane. Cl—SiR3, to yield a trialkylsilyl ether, R -O-SiR. Chlorotrimethylsilane is often used, and the reaction is carried out in the presence of a base, such as triethylamine, to help form the alkoxide anion from the alcohol and to remove tfie HCl by-product from the reaction. 

The last variable, the nature and concentration of the amine catalysts used, requires a more detailed analysis to understand its importance. Most of the early work on preparing cyclics was based on the use of triethylamine since much of the literature on the preparation of polycarbonates has centered around this catalyst. As the importance of the catalyst became more fully realized, a variety of other amines were tested to help determine the role of the catalyst. Ultimately, it was desirable to determine if the catalyst functioned as a general base catalyst or as an acylation catalyst similar to the hyper-nucleophilic amine 4-dimethylaminopyridine (see Scheme 3). If general base catalysis were the sole function of the amine, then classical phase-transfer catalysts and very basic amines should prove to be... 

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