Alcohols high-yield requirements

The reaction of small amounts of an alcohol with an NCA results in initiation of polymerization and even with large amounts of alcohol high yields of esters are not obtained, since the amine formed from esterification is nucleophilic and reacts preferentially with another NCA. Thus the preparation of esters from NCAs requires at least one equivalent of HCl. High yields of esters are obtained from the reaction of an alcohol and an NCA under anhydrous conditions and saturation with... 

Montedison and Mitsui Petrochemical iatroduced MgCl2-supported high yield catalysts ia 1975 (7). These third-generation catalyst systems reduced the level of corrosive catalyst residues to the extent that neutralization or removal from the polymer was not required. Stereospecificity, however, was iasufficient to eliminate the requirement for removal of the atactic polymer fraction. These catalysts are used ia the Montedison high yield slurry process (Fig. 9), which demonstrates the process simplification achieved when the sections for polymer de-ashing and separation and purification of the hydrocarbon diluent and alcohol are eliminated (121). These catalysts have also been used ia retrofitted RexaH (El Paso) Hquid monomer processes, eliminating the de-ashing sections of the plant (Fig. 10) (129). 

The esterification of boric oxide does not require the removal of water. However, if high yields based on boron are desired, six or more moles of alcohol must be used and the water must be removed. 

A reagent which is primarily of interest as a means of converting alcohols into fluorides has been used to dehydrate C-11 alcohols in high yields. 1 la-Alcohols dehydrate rapidly with 2-chloro-l-diethylamino-l,l,2-trifluoro-ethane reagent at low temperature, while 11 j5-alcohols require refluxing methylene chloride. Traces of fluoro compounds have been detected in the products. 

The relatively poor resonance activation of the 2-Le-3-aza orientation in bicyclics (cf. Section IV, A) is illustrated by nucleophilic substitutions below. Vigorous conditions are required for methoxylation (110°, 17 hr, quantitative yield) of 3-bromocinnoline and for amination (aqueous ammonia, copper sulfate, 20 hr, high yield) of 3-bromo- (at 130°) or of 3-chloro-derivatives (at 165°). 3,4-Dichlorocinnoline gives predominantly 4-substitution in hydra-zination (90% yield, 20°, 4 days in alcohol), amination (70% yield, 150°, 22 hr in alcohol), and hydroxylation (50% yield, 150°, 22 hr, aqueous ammonia). The poorer-leaving phenoxy group in 3-chloro-4-phenoxycinnoline, is displaced with ammonium acetate (160°, few mins, 60% yield). ... 

Reaction with alcohols is general for diazo compounds, but it is most often performed with diazomethane to produce methyl ethers or with diazo ketones to produce ot-keto ethers, since these kinds of diazo compounds are most readily available. With diazomethane the method is expensive and requires great caution. It is used chiefly to methylate alcohols and phenols that are expensive or available in small amounts, since the conditions are mild and high yields are obtained. Hydroxy compounds react better as their acidity increases ordinary alcohols do not react at... 

In situ production of phosphine-free CuH from CuCl or CuOAc (0.3-1.0 equivalents), in the presence of an excess of PhMe2SiH in DM I at room temperature, displays a remarkable preference for reductions of aryl ketones (e.g., 15) over aliphatic ones such as 16 (Eq. 5.23) [46]. Reactions require a day or more to reach completion, concentrations of 0.5 M notwithstanding, but yields have been uniformly good (77-88%) for the few cases examined. Aldehydes, however, show no such selectivity and are reduced to the corresponding primary alcohols, albeit in high yields. 

Results for the oxidation of primary alcohols using catalyst 8 are summarized in Scheme 5.6. While larger quantities of the catalyst (0.50 mol% Ir) and acetone were required, the oxidation of primary alcohols proceeded selectively in good to high yields. 

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