2,5-Hexanedione, 3,4-diacetyl

DlmethylpyrazoM -yl)pentane-2,4-dlone (3). To a stirred suspension of diacetyl hexanedione 1 (2.0 g, 10 mmoO in boiling ElOH (SO mL) was added hydrazine hydrate 2 (0.6 mL). The clarified (charcoal) hot solution was evaporated in vacuum arxi the oily residue was crystallized from water to afford 0.9 g of 3 (4614), mp 134-140°C. 

Diketones are synthesized by Claisen condensation of appropriate acetyl methyl ketone and ethyl perfluoroalkyl carboxylate. For example, 4,4/-bis(l",l,/,l//,2//,2",3//,3//-heptafluoro-4//,6//-hexanedion-6"-yl)-chlorosulfo-o-terphenyl (BHHCT) was synthesized from o-terphenyl by three step reactions (scheme 3 (Yuan et al., 1998a, 1998b)). The o-ter-phenyl are acetylated by acetyl chloride with anhydrous aluminum chloride as a Lewis acid and 4,4 -diacetyl-e>-terphcnyl is obtained. Then, the 4,4/-diacetyl-o-terphenyl is reacted with perfluoropropionic acid ethyl ester with sodium methoxide as a base. Finally, 4,4,-bis(l", 1",l//,2,2,3,/,3"-heptafluoro-4//,6"-hexanedion-6//-yl)-o-terphenyl is chloro-sulfonylatcd by chlorosulfonic acid to form BHHCT. 

Recently isolated from baker s yeast are two diacetyl reductases. One enzyme shows a high S and the other a high R selectivity for the reductions of 2,3-pentanedione, 2,3-hexanedione and other mono- and dikctoncs218. 

Hexanedione has a powerful, creamy-sweet, heavy-buttery, oily odor, yet somewhat milder than diacetyl. The odor is often classified as quinone-like . The taste is buttery-cheesy, particularly in acid medium (Arctander, 1967). The flavor is fatty, fruity, pear-like (Chemisis, 1961). 

Diketobutane. See Diacetyl 4,4 -Diketo-p-carotene. See Canthaxanthine 2,5-Diketohexane. See 2,5-Hexanedione... 

The products [Ni(L1815)] to [Ni(L1820)] are obtained by template condensation of sulphur-substituted isothiocarbohydrazides with diacetyl monoxime, 1,2-cyclo-hexanedione monoxime or isonitrosoacetone in the presence of nickel salts in boiling methanol followed by neutralisation with pyridine. Chromatographic separa-... 

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