3- Acetyl-4-hydroxy-6-methyl-pyron

Dehyracetic acid 2-Acetyl-5hydroxy-3-oxo-4-hexenoic acid delta-lactone 3-Acetyl-4-hydroxy-6-methyl-pyron... 

An aq. soln. of 5-carbethoxy-2- -hexyl-2,3-dihydro-6-methyl-4-pyrone and NaOH stirred 24 hrs. at 0-2°, then acidified with HCl -> 3-acetyl-6- -hexyl-5,6-dihydro-4-hydroxy-2-pyrone. Y 77.9%. K. Sato, S. Inoue, and M. Ohashi, Bull. Chem. Soc. Japan 46, 1288 (1973). 

NMR spectra were measured. As RuCl(H20)(csb)2/02/Me2CHCH0/CH2Cl2/4°C it asymmetrically epoxidised styrene and substituted styrenes with e.e. of up to 30% [798]. Complexes with (csb =lR,2R(-)l,2-diaminocyclohexane with 3-acetyl-4-hydroxy-6-methyl-2-pyrone and salicylaldehyde, 5-chloro-5-methoxy, 5-methoxy and 5-nitrosalicyladehyde) asymmetrically epoxidised styrene as RuCKH O) (csb )2/PhIO/CH3CN [799]. 

The most common method for the preparation of pyrazoles from other heterocycles is from pyranone-type compounds. Condensation of 2,3-dihydro /7-pyran -ones 787 with various aryl hydrazines in the presence of montmorillonite KSF clay under mild conditions proceeded rapidly to afford enantiomerically pure 5-substituted pyrazoles 788 (Equation 172) <2004TL6033>. Comparable results were obtained when arylhydrazines were reacted with 2-formyl glycals under microwave irradiation <2004TL8587>. Phenylhydrazine and hydrazine were reacted with 3-acetyl-4-hydroxy-6-methyl-2/7-pyran-2-one to afford 4-acetoacetyl-3-methylpyrazolin-5-ones, which were employed in the synthesis of bipyrazoles and pyrazoloisoxazoles <1999JHC1291>. Reaction of 3,3-dialkyl-6-(trifluoromethyl)-2,3-dihy-dro -pyrones with hydrazine hydrate afforded 3-(trifluoromethyl)-5-substituted-pyrazoles <1998RCB1365>. 

Mit zwei mol Hydrazin werden aus 3-Acetyl-4-hydroxy-4-methyl-2H-pyron Bi-(1 H-pyrazo-lyle) erhalten299,1184,2457 [s.Bd.X/2, S.681 (1968)]. Zur Reaktion von 4H-Pyron mit Phenyl-hydrazin s.Bd.X/2, S.678 (1968). 

Acetylacetone and malonyl chloride give 5-acetyl-4-hydroxyd-methyl-2-pyrone (XII-253), a positional isomer of dehydroacetic acid, which reacts with aqueous ammonia or aqueous methylamine to form XII-254 (R = H, CHs), which can also be prepared from the enamine of acetylacetone and carbon suboxide (see Section I.3.E., p. 635). The //-methylpyridone XII-2S4 (R = CH3) is deacetylated to 4-hydroxy-l,6-dimethyl-2-pyridone with sulfuric acid however, W-254 (R = H) was not deacetylated under these conditions. Acetylacetone and carbon suboxide give 8-acetyl-4-hydroxy-7-methylpyrano-[4,3-6] pyiane-2,5-dione (XI-255) with catalytic amounts of sulfuric acid. This is also formed from acetylacetone and malonyl chloride or from carbon suboxide and the intermediate 5-acetyl-4-hydroxy-6-methyl-2-pyrone (XU-253). 3,5-Diacetyl-4-hydroxy-6-methyl-2-pyrone (XI-256) can be formed by acetylation of XII-253 with acetic acid and phosphorus oxychloride or by degradation of XII-255. 3,5-Diacetyl-4-hydroxy-6-methyl-2-pyridone can... 

Acetyl-4-hydroxy-6-phenyl-2-pyridone, 635 from 5-acetyl-4-hydroxy-6-phenyl-(2tf)-2-pyrone, 658 5-benzoyl-4-hydroxy-6-methyl-(2f )-2-pyrone, 658... 

Methyl-l-phenyl-4-benzoylpyrazolone ( 27 14 2 2 3-Acetyl-2-hydroxy-6-raethyl-4-pyrone (dehydracetic acid) (CgH3E>3) 6-Ethyl-2-hydroxy-3-propionyl-4-pyrone... 

When, diphenylthiourea was allowed to condense with malonyl dichloride, l,3-diphenyl-2-thiobarbituric acid (XLV) was formed together with a 25 per cent yield of 4,5-dioxo-l,3-diphenyl-7-hydroxy-2-thiopyrano[2,3-d]pyrimidine (XLIV) [31]. It is possible that (XLIV) is produced by the reaction of an excess of malonyl dichloride on (XLV), formed initially. On methylation with diazomethane, the 7-methoxy derivative of (XLIV) is formed [31]. When heated in pyridine, the pyrone (XLIV) decomposes to give 5-acetyl-l,3-diphenyl-2-thiobarbituric acid [31]. 

Hydroxy-5-oximino-7-methyl-5i/-pyrano[2,3-6]pyridine 8-oxide, formed by the action of dimethylformamide dimethyl acetal on 3-acetyl-4-hydroxy-6-methyl-a-pyrone, has been shown by C n.m.r. to exist as structure (153), one of... 

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