Of 1,3-diols

Much of the chemistry of diols—compounds that bear two hydroxyl groups—is analo gous to that of alcohols Diols may be prepared for example from compounds that con tain two carbonyl groups using the same reducing agents employed m the preparation of alcohols The following example shows the conversion of a dialdehyde to a diol by... 

Diols are almost always given substitutive lUPAC names As the name of the prod uct m the example indicates the substitutive nomenclature of diols is similar to that of alcohols The suffix dwl replaces ol and two locants one for each hydroxyl group are required Note that the final e of the parent alkane name is retained when the suffix begins with a consonant ( diol) but dropped when the suffix begins with a vowel ( ol)... 

A procedure using 48% HBr with a Dean-Stark water trap gives good yields of 4-bromobutanol [33036-62-3] free of diol and dibromo compound... 

Plasticizers. About 2.5% of U.S. adipic acid consumed in 1988 was used in two basic types of adipic ester based plasticizers (195). Simple adipate esters prepared from Cg—alcohols are used especially as PVC plasticizers (qv). Eor special appHcations requiring low volatility or extraction resistance, polyester derivatives of diols or polyols are preferred. 

Alkah manganate(VI) salts are used as oxidants in synthetic organic reactions (100) and their reactions have been observed to be similar to permanganate, except that manganate(VI) exhibits lower reactivity. Additionally, sohd BaVInO in methylene chloride has been reported to achieve high yields for the oxidation of diols to dialdehydes (101). 

Trickle bed reaction of diol (12) using amine solvents (41) has been found effective for producing PDCHA, and heavy hydrocarbon codistiUation may be used to enhance diamine purification from contaminant monoamines (42). Continuous flow amination of the cycloaUphatic diol in a Hquid ammonia mixed feed gives >90% yields of cycloaUphatic diamine over reduced Co /Ni/Cu catalyst on phosphoric acid-treated alumina at 220°C with to yield a system pressure of 30 MPa (4350 psi) (43). 

Polyester polyols are based on saturated aHphatic or aromatic carboxyHc acids and diols or mixtures of diols. The carboxyHc acid of choice is adipic acid (qv) because of its favorable cost/performance ratio. For elastomers, linear polyester polyols of ca 2000 mol wt are preferred. Branched polyester polyols, formulated from higher functional glycols, are used for foam and coatings appHcations. Phthalates and terephthalates are also used. 

Adipoyl moiety is first attached ia order to provide an appropriately spaced proximal carbonyl group. The esters are oxidized enzymatically and then deacylated. The procedure results ia the synthesis of diols (119) with excellent enantiomeric purity (ee 96—98%) ia 72—92% yield. 

Sulfurane reagent lor conversion of trans diols to epoxides, generally for dehydration of diols to olefins or cyclic ethers, and as an oxidizing agent... 

Mono MOM derivatives of diols can be prepared from the ortho esters by diiso-butylaluminum hydride reduction (46-98% yield). In general, the most hindered alcohol is protected. ... 

The prevalence of diols in synthetic planning and in natural sources (e.g., in carbohydrates and nucleosides) has led to the development of a number of protective groups of valuing stability to a substantial array of reagents. Dioxolanes and diox-anes are the most common protective groups for diols. The ease of formation follows the order ... 

The DTBS group is probably the most useful of the bifunctional silyl ethers. Di-methylsilyl and diisbpropylsilyl derivatives of diols are very susceptible to hydrolysis even in water and therefore are of limited use. 

This reaction is significantly exothermic. Stronger cooling as from an acetone-dry ice bath can he employed if desired to expedite the addition of diol. In any event, a temperature in excess of 20 leads to unwanted rapid hydrolysis and formation of water-soluble byproducts. 

The third approaeh to synthetic polymers is of somewhat less commereial importance. There is in fact no universally accepted deseription for the route but the terms rearrangement polymerisation and polyaddition are commonly used. In many respects this process is intermediate between addition and condensation polymerisations. As with the former teehnique there is no moleeule split out but the kinetics are akin to the latter. A typical example is the preparation of polyurethanes by interaction of diols (di-alcohols, glycols) with di-isocyanates Figure 2.7). 

Chromatography of 3, 17jS-dihydroxypregn-5-en-20-one (82a) on alumina affords the rearranged product 3/ ,17a/ -dihydroxy-17aa-methyl-D-homo-androst-5-en-17-one (84a) in quantitative yield.On the other hand, treatment of diol (82a) or diacetate (82b) with methanolic potassium hydroxide... 

For the selective protection of diols Bu2SnO, benzene, reflux MOMCl, Bu4N r, It, 87% yield. ... 

BnX (X = Cl, Br), Ag20, DMF, 25°, good yields. This method is very effective for the monobenzylation of diols. ... 

Bu3Sn)20 BzCl. The use of microwaves accelerates this reaction. Bu2Sn(OMe)2 is reported to work better than Bu2SnO in the monoprotection of diols. The monoprotection of diols at the more hindered position can be accomplished through the stannylene if the reaction is quenched with PhMe2SiCl (45-77% yield).Microwave heating has been found to be effective for this transformation in some cases. ... 

The use of chiral ketones for the protection of diols serves two purposes first, diol protection is accomplished, and second, symmetrical intermediates are converted to chiral derivatives that can be elaborated further, so that when the diol is deprotected, the molecule retains chirality. ... 

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