Esters, Ethers, and Related Derivatives of Alcohols

Selective hydrolysis of the 3a-acetoxy-group of fully acetylated cholic acid derivatives has been achieved with methanolic HCl. The hydrolysis occurs more rapidly than the methylation of the side-chain carboxylic acid. The 3-monosulphates of cholic, chenodeoxycholic, and deoxycholic acids have been prepared using this selective hydrolysis on the fully acetylated methyl esters. The resultant 3a-hydroxy-compounds were then treated with chlorosulphonic acid and the 

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Ethers, Esters, and Related Derivatives of Alcohols.—Oestrogens are effectively methylated at the phenolic oxygen by extraction from alkaline solution into di-chloromethane containing iodomethane, with a tetra-n-hexylammonium salt as a phase-transfer reagent ( extractive alkylation ). Conditions are mild, and the reaction is very rapid. In combination with g.l.c. analysis of the methyl ethers, it provides a simple and convenient method for the analysis of oestrogen mixtures. H-... 

Ethers, Esters, and Related Derivatives of Alcohols.—5a-Cholestanyl methyl ether has been cleaved inter alia) and converted into 5a-cholestanol by successive treatment with trimethylsilyl iodide and water.Pyridinium toluene-p-sulphonate has been reported as an efficient and mild catalyst for the conversion of alcohols into their tetrahydropyranyl ethers.Bile acids were efficiently performylated by treatment with 90% HCO2H-HCIO4. Selective base-catalysed... 

Esters, Ethers, and Related Derivatives of Alcohols.— The long-recognized differences in reactivity of the 3a-, 7a-, and 12a-hydroxy-groups in cholic acid to acetylation (3a > 7a > 12a) have been attributed to conformational and steric effects [3a-equatorial 7a- and 12a-axial, and seemingly differentiated by greater steric hindrance at C(12), due to the side-chain]. A new investigation, however, shows that the reactivities of the monohydroxycholanic acids are in ratio 3a 7a 12a 97 1.0 1.5. ° A novel radioisotope method was used for... 

Nucleophilic Substitution Solvolytic and Elimination Reactions Ring-opening of Epoxides Esters, Ethers, and Related Derivatives of Alcohols Oxidation Reduction Miscellaneous... 

Esters, Ethers, and Related Derivatives of Alcohols.— Although acetylation with acetic anhydride-pyridine is one of most familiar reactions, the detailed mechanism does not seem to have been elucidated.Spectroscopic detection of the acetylpyridinium ion resulting from the equilibrium ... 

Esters, Ethers, and Related Derivatives of Alcohols.— The mode of transmission of the effect of remote substituents upon reaction rates and equilibria has been discussed previously under three headings, viz. inductive effects, electrostatic field effects, and conformational transmission.A new survey,quoting over 50 references, covers most of the main studies in this field, and suggests direct interactions as a fourth class. Rates of acetylation of 3j3-hydroxy-A"-steroids variously substituted at C-17 show only small variations, which did not permit of any mechanistic interpretation. The formation of 17a,20- and 20,21-cyclic carbonates and their use as protecting groups for diols have been investigated. ... 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Esters or ethereal salts are derivatives of alcohols formed by the reaction of an alcohol with an acid. As they are thus acid derivatives also and as the more important esters are those formed from the organic acids, which we shall soon study, the chief discussion of them as a group will come later. There are, however, to be considered the esters formed from inorganic acids and these will be presented now. The chemical properties of alcohol in its relation to both bases and acids are of especial interest and importance. We have spoken of the fact that alcohol as an hydroxyl compound belongs to the water type, and that the other representatives of this type are the metal hydroxides or bases, and the non-metal hydroxides or acids. 

According to Montedoro G. et al [12] and Tiscomia et al [3] different volatile constituents are found in virgin olive oil. They account for approximately 150 compounds of several chemical classes aliphatic and aromatic hydrocarbons, aliphatic alcohols, oxygenated terpens, aldehydes, ethers, ketones, thiophene and furane derivatives, esters (table 1) all these compounds confer on the virgin oil the characteristic aromatic notes. In particular C(> aldehydes and related alcohols (hexanale, cis-3-... 

Lipids are defined as organic substances soluble in solvents regarded as fat-like, i.e., chloroform, carbon tetrachloride, benzene, diethyl ether, petroleum ether, etc., and which are related actually or potentially to esters of the long-chain fatty acids. A simple classification scheme which illustrates the role of these fatty acids in lipid chemistry is given in Table VI. It can be seen that most combined lipids consist of esters with long-chain alcohols, sterols, vitamins or, most commonly, glycerol and its substituted derivatives, viz., RCOOM where R = alkyl chain and M is an alcoholic moiety. 

Allylic alcohols, esters, and ethers undergo acid-catalyzed isomerizations, and allylic alcohols and ethers isomerize at appreciable rates only in the presence of acids. The migrating groups in these reactions are uncharged molecules derived from the oxonium ion conjugate acids of the starting materials. For this reason, and because they are mechanistically related to anionotropic isomerizations, Braude named these reactions oxotropic rearrangements. 

Hydroborations. Addition of Catecholborane to alkenes is accelerated by Wilkinson s catalyst, and other sources of rhodium-(I) complexes. Unfortunately, the reaction of Wilkinson s catalyst with catecholborane is complex hence if the conditions for these reactions are not carefully controlled, competing processes result. In the hydroboration of styrene, for instance, the secondary alcohol is formed almost exclusively (after oxidation of the intermediate boronate ester, eq 37) however, the primary alcohol also is formed if the catalyst is partially oxidized and this can be the major product in extreme cases. Conversely, hydroboration of the allylic ether (12) catalyzed by pure Wilkinson s catalyst gives the expected alcohol (13), hydrogenation product (14), and aldehyde (15), but alcohol (13) is the exclusive (>95%) product if the RhCl(PPh3)3 is briefly exposed to air before use. The 5yn-alcohol is generally the favored diastereomer in these and related reactions (eq 38), and the catalyzed reaction is therefore stereocomplementary to uncatalyzed hydroborations of allylic ether derivatives. ... 

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