Pinacol, anhydrous

Pinacol (anhydrous) [76-09-5] M 118.1, m 41.1°, b 172°. The hydrate is rendered anhydrous by azeotropic distn of water with benzene. Recrystd from benzene or toluene/pet ether, absolute EtOH or dry ethyl ether. Recrystn from water gives the hexahydrate. 

Work up the product by method (a) or (b) method (6) affords the anhydrous pinacol. 

Add about 60 ml. of petroleum (b.p, 60-80°) with stirring to the fraction of b,p, 150-180°, thus precipitating the pure anhydrous pinacol (2 5-3 8 ) Filter this off, and then shake the filtrate with ca. 4 ml, of water the remaining pinacol now separates as the hexahydrate (5 g.). The two crops may be united and recrystallised from ca. 10 ml, of water (total yield of hexahydrate, 8-9 g,). Dry and bottle the product rapidly as described in (a). 

The anhydrous compound, pinacol, is a liquid it may be prepared from the hydrate by azeotropic distilktion with benzene. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

The excess of trimethylamine was removed by washing the pinacol (R)-( )-2-(3-trimethylsiloxy-l-butene)boronate (5.0 g) in petroleum ether (50 mL) using 5% aqueous AcOH (10 mL), 4% aqueous NaHCOs (10 mL), and saturated aqueous Na2S04 solution. The aqueous phases were back extracted each time with petroleum ether (10 mL). The combined organic layers were dried over anhydrous MgS04, filtered, and the solvent was removed under reduced pressure to afford pure pinacol ( )-2-(3-trimethylsiloxy-l-butene)boronate (4.84 g). Co(N03)2 6H20 (20 mg, 0.069 mmol) was added to a stirred solution of pinacol (R)-( )-2-(3-trimethylsiloxy-l-butene)boronate (5.70 g, 21.1 mmol) in petroleum ether (130 mL). Freshly distilled SOCI2 (2.75 g, 23.1 mmol) was added, and... 

Anhydrous pinacol (I) is catalytically decomposed by aqueous hydrobromic acid into dimethyl butadiene (II) and pinacolone (III) separation is effected by distillation through an efficient fractionating column ... 

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