4H-pyran-4-one, 2,6-Dimethyl

C7H1202 tetrahydro-2,6-dimethyl-4H-pyran-4-one 1073-79-6 447.69 38.882 2 11590 C7H13CI 2-ch loro-1-heptene 65786-11-0 412.15 33.867 1.2... 

Nucleophiles attack 4H-pyran-4-ones on C-2 or C-4. With aqueous alkali, 1,3,5-triketones are formed by addition of hydroxide ions to C-2 for instance, 2,6-dimethyl-4H-pyran-4-one 5 affords heptane-2,4,6-trione 6 ... 

Dimethyl-4H-pyran-4-one (17), mp 132 °C, is water soluble. It is obtained by several methods, the simplest utilizing the self-condensation of acetic anhydride mediated by polyphosphoric add at elevated temperature a probable intermediate is the mixed anhydride of acetoacetate 16 ... 

Dimethyl-4H-pyran-4-one is O-alkylated by CH3I, which was established by converting the resulting pyrylium salt 19 into 4-methoxy-2,6-dimethylpyridine (18) with NH3 (Baeyer, 1910). 

Also obtained by heating 3-acetyl-2,6-dimethyl-4H-pyran-4-one with sodium ethoxide in ethanol (17%) [2940]. 

Adedeji et al. (1993) used a direct thermal desorption technique (220°C) to analyse the volatiles from beans that might cause the thermal degradation and transformation of sugar into common volatile compounds such as 3,5-dimethyl-2,4(3H,5H)-furandione and 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one. This last compound was detected at a high concentration (3880 ppm) in Mexican vanilla, being the third most abundant compound after vanillin and 2-furfural, and far more abundant than vanillic acid, p-hydroxy-benzaldehyde or p-hydroxybenzoic acid. 

Only two Anobiidae pheromones have been identified thus far. The drugstore beetle, Stegobium panlceum (L.), pheromone was identified as 2,3-dihydro-2,3,5-trimethyl-6-(l-methyl-2-oxo-butyl)-4H-pyran-4-one (XIV) (44) and the cigarette beetle, Lasloderma serrlcorne F., as 4,6-dimethyl-7-hydroxy-nonan-3-one (XV) (45). The similarity of these structures is worth noting. 

The pyran indicated, 2,3-dihydro-2,2-dimethyl-6-phenyl-4H-pyran-4-one and benzoylacetylene in chloroform containing 2.5 moles of 2,6-di-tert-butylpyridine unden/vent additton in the presence of excess triisopropylsilyl triflate by stirring... 

Hydroperoxy-4,9-dimethyl-6-methylenedeca-2,4-dien-2-yl)-6-methoxy-3,5-dimethyl-4H-pyran-4-one (136)... 

Methylene blue (14.0 mg, 0.0400 mmol) was added to a solution of 2-methox y-3,5-dimethyl-6-((2Zt,4Zt,6 )-4,6,9-trimethyldeca-2,4,6-trien-2-yl)-4H-pyran-4-o ne (44) (70.0 mg, 0.210 mmol) in methanol (70 mL). The mixture was purged with oxygen for 30 min via an oxygen balloon and outlet needle, after which time the outlet needle was removed, and the solution irradiated for 24 h. The mixture was then concentrated under reduced pressure, and the residue purified by flash column chromatography to afford 2-((2 , 4 )-7-hydroperoxy-4,9-dimethyl-6-methylenedeca-2,4-dien-2-yl)-6-methoxy-3,5-dimethyl-4H-pyran-4-one (136) (4.0 mg, 5 %) as a colourless oil. 

This overview deals with some of the chemical marker compounds suited to the requirements of quality control laboratories in the citrus industry. Chemical markers include ascorbic acid, dehydroascorbic acid, hydroxymethylfurfural, furfural, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 4-vinyl guaiacol and a-terpineol. Some of these compounds might be applied as useful tools in evaluating quality deterioration due to unsuitable manufacturing and storage as well as for the computation and optimization of the manufacturing processes and parameters. Since they are all chemically reactive compounds, careful evalution of kinetics of these compounds is necessary. 

H- Pyran-4-one, 3,5-diacetyl-2,6-dimethyl-dipole moment, 3, 626 (37JCS1088) 4H-Pyran-4-one, 2-dichloromethyl- C NMR, 3, 588 (82S500)... 

Propanol with magnesium in reduction of chlorobenzene, 47, 104 Propionyl fluoride, 46, 6 n Propylamine, 46, 85 n Propylhydrazine, 46, 85 C ( Propyl) N phenylmtrone, genera tion from phenylhydroxylamme and n butyraldehyde, 46, 97 Purification of tetrahydrofuran (Warning), 46,105 4H Pyran 4-one, 2 6 dimethyl 3,5 diphenyl, 47, 54... 

Used for the preparation of 2,6-dimethyl-3,5-diphenyl-4H-pyrane-4-one and tetraphenylcyclopentadienone. 

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