Vicinal glycols, oxidation

Lead(fV) ethanoate, Pb(02CCH3)4, (Pb(ll)ethanoate plus CI2) is a powerful oxidizing agent which will convert vicinal glycols to aldehydes or ketones and 1,2-dicarboxylic acids into alkenes. Primary amides give ketones and amines give nitriles. 

Vicinal glycols may be oxidized to the corresponding 17a-hydroxy-20-ketones in reasonable yields by means of chromium trioxide in dimethylfor-mamide in the presence of manganese dichloride, or by treatment with dimethyl sulfoxide-acetic anhydride. ... 

It is an important reagent for the oxidative cleavage of vicinal glycols which are oxidised at room temperatures to aldehydes, ketones or both depending on the nature of glycol. 

The mechanism of oxidation of vicinal glycols by HI04 has been studied by G.J. Buisst and C.A. Bunton (J. Chem. Soc., 1406, (1954). According to these workers, the reactive species is the para form of periodic acid (H5I06) which is formed by the action of water on HI04. 

Reagents that specifically oxidize vicinal glycols [e.g., NaI04, Pb-(02CCH3)4, and NaBi03 Section 16-9A] are quite helpful in determining the cyclic structures of sugars. With periodate, the numbers of moles of oxidant consumed and the moles of methanoic acid and methanal produced are... 

Criegee reaction. Oxidative cleavage of vicinal glycols by lead tetraacetate. 

Oxidation of vicinal glycols of haptens with NaI04and conjugation to protein Coupling of adenosine to BGase (Lauer and Erlanger, 1971)... 

We may recall the well-known reactions of these two oxidants on vicinal glycols, reactions (5.16) and (5.17). 

An alkene can be oxidized to a 1,2-diol either by potassium permanganate (KMn04) in a cold basic solution or by osmium tetroxide (OSO4). The solution of potassium permanganate must be basic, and the oxidation must be carried out at room temperature or below. If the solution is heated or if it is acidic, the diol will be oxidized further (Section 20.8). A diol is also called a glycol. The OH groups are on adjacent carbons in 1,2-diols, so 1,2-diols are also known as vicinal diols or vicinal glycols. 

Rosenmund reduction (p. 845) Swern oxidation (p. 851) Tollens test (p. 853) vicinal diol (p. 858) vicinal glycol (p. 858)... 

Epoxide rings are cleaved by treatment with acid just as other ethers are. The major difference is that epoxides react under much milder conditions because of ring strain. Dilute aqueous acid at room temperature is sufficient to cause the hydrolysis of epoxides to 1,2-diols, also called vicinal glycols. (Th word vicinal means adjacent," and a glycol is a diol.) More than 3 millii-tons of ethylene glycol, most of it used for automobile antifreeze, are product each year in the United States by acid-catalyzed hydration of ethylene oxid Note that the name ethylene glycol refers to the glycol derived from ethylen just as ethylene oxide refers to the epoxide derived from ethylene. 

Non vicinal glycols can also be selectively oxidised the results for 1,3 propanediol and diethyleneglycol oxidation, reported in Table 13.6, indicate a lower reactivity than the vicinal diols reported in Table 13.3, whereas the selectivity to monocarboxylates was always very high. 

Jn a potentially far reaching application for melt catalysis by the transition metals, we at Texaco have demonstrated the synthesis of a range of commodity chemicals and fuels directly from CO/H2 via the use of ruthenium-containing molten salt catalysis. Products include ethylene glycol, Ci-C4 alcohols, acetic acid, acetate esters, C2+ olefins and vicinal glycol esters. In its simplest form, this new class of melt catalyst comprises one or more ruthenium sources, e.g. ruthenium carbonyls, oxides, complexes, etc. dispersed in a low-melting (m.p. <150 C) quaternary phosphonium or ammonium salt (e.g. tetrabutylphos-phonium bromide). The key components are selected such that ... 

The structure of hyocholic acid was proposed by Haslewood (24) and by Ziegler (7) to be 3a,6a,7 -trihydroxy-5 -cholanic acid (I, Fig. 1). Since it was known that pig bile contains hyodeoxycholic acid (3a,6a-dihydroxy) and chenodeoxycholic acid (3a,7a-dihydroxy) the bile was assumed to contain possibly also an acid with both 6a- and 7a-hydroxyl groups. Chemical evidence for the vicinal glycol structure in hyocholic acid was found after chromic oxidation. The product, 3-keto-6,7-secocholanic acid-6,7-dioic... 

---