Dihydroxybenzoic acid hydrogenation

Scheme 2.1 Schematic representation of intramolecular molecular dynamics in hydrogen-bonded 2,6-dihydroxybenzoic acid.

Dihydroxybenzoic acid (18.8 g, 120 mmol), butanol (23 mL, 250 mmol), and H2SO4 (3-4 mL, cone.) are refluxed in toluene previously dried over sodium (25 mL) in a flask equipped with a Teflon-coated magnetic stirrer and a Dean-Stark trap for 9 h. On completion of the reaction (as revealed by TLC), the product is poured into water and extracted with ether. Washing with sodium hydrogen carbonate solution and then water followed by recrystallizing from petroleum ether (60-80 fractions) gives the product as a white solid. 

On hydrogenation of 3,5-dihydroxybenzoic acid with Raney nickel catalyst W1 (see Billica and Adkins155), 3,5-dioxocyclohexanecarboxylic acid is obtained.228 Hydrogenation of 3-ethylphenol with Raney nickel leads to 3-ethy Icy clohexanol.229... 

Benzodioxins.—A synthesis of 5- and 8-hydroxy-l,3-benzodioxin-4-ones from 2,6- and 2,3-dihydroxybenzoic acid, dibromomethane, and benzaldehyde diacetate has been described. AA -Carbonyldi-imidazole reacts with 2-hydroxybenzamide to give the 1,3-benzodioxin in 72% yield (Scheme 9). Amides which lack intramolecular hydrogen-bonding react differently. ... 

The highly cross-linked 12 % agarose gel, Superose 12 HR 10/30, possesses hydrogen bond acceptor properties suitable for the separation of polyphenolic solutes such as phenolic acids, flavonols, and flavonoids. The separation is achieved isocratically in the presence of solvent mixtures of acetic acid and ethanol. The extent of hydrogen bond adsorption is reviewed based on data obtained from the elution behavior of a variety of simple polyphenolic solutes including dihydroxybenzoic acids [39,40]. 

Fricke H, Bartl K, Funk A, Gerlach A, Gerhards M (2008) Proton/hydrogen-transfer coordinate of 2,5-dihydroxybenzoic acid investigated in a supersonic beam combined IR/LTV spectroscopy in the So, Sj, and Do states. ChemPhysChem 9(17) 2592-2600... 

Figure 4. MALDI-TOF mass spectrum of the hydrogen-bonded assembly )3 (DEB)6 after complexation of Ag between two aromatic jc-donors (matrix 2,5-dihydroxybenzoic acid)...

The reaction of dithiocarbamates and diselenocarbamates with a-halogenated carbonyl compounds has proved to be a useful first step in the synthesis of l,3-dithiole-2-thiones and their analogues. Thus 2-dimethylamino-l,3-dithiolium salts (38) > and diselenolium salts (39) " are readily obtainable by this route, and these salts are converted into thiones (40 X = Y = S or Se, Z = S) or selones (40 X = Y = S or Se, Z = Se) with hydrogen sulphide or hydrogen selenide. The dihydroxybenzo-l,3-dithiole-2-thione (41) has been prepared from p-benzoquinone and dithiocarbamic acids. ... 

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