Brominated derivatives of 4-hydroxy- and 4-methoxy-6-methyl-2H-pyran-2-ones

Twenty-five different brominated derivatives of 4-hydroxy-6-methyl-2-pyrone (triacetic acid lactone) and 3-acetyl-4-hydroxy-6-methyl-2-pyrone (dehydroacetic acid) have been prepared. Fifteen derivatives have not been previously described and the preparations of a few known products have been improved. Bromination at C-3, C-5, methyl group at C-6 and deacetylations at C-3 have been the types of reactions used.     

Iodocyclization of N,N-dialkylamino-2-methyl-4-penten-2-ol oxides

It is shown that in the iodination of N,N-dialkylamino-2-methyl-4-penten-2-ol and N,N-diethylamino-3-butene oxides the N-oxide group participates in the intramolecular cyclization of these compounds. N,N-Dialkyl-4-methyl-4-hydroxy-6-iodomethyltetrahydro-1,2-oxazine iodides were obtained by iodination of the former, whereas the latter under similar conditions gives N,N-diethyl-5-iodomethyltetrahydro-1,2-oxazolinium iodide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1340–1343, October, 1976.     

Enzymatic resolution of 4-methyl-, 4-phenyl- and 6-phenyltetrahydro-2H-pyran-2-one using esterases

Enantioselective hydrolysis of racemic tetrahydro-2H-pyran-2-ones (δ-valerolactones) using esterase resulted in the formation of optically active (R)-4-methyl-, (R)-4-phenyl- or (R)-6-phenyltetrahydro-2H-pyran-2-ones and the corresponding (S)-8-hydroxypentanoic acid derivatives.     

Antioxidant activity of 2-methyl-1,3-benzoxazol-6-ol

Antioxidant effect of 2-methyl-1,3-benzoxazol-6-ol in radical chain oxidation of organic compounds with molecular oxygen was studied. Antiradical activity in the reaction with stable diphenylpicrylhydrazyl radical was examined by photocolorimetry. The kinetic parameters of the reaction of 2-methyl-1,3-benzoxazol-6-ol with peroxy radicals of different natures were determined by volumetric and chemiluminescence methods. A relation was found between the antioxidant activity and electronic structure parameters calculated by quantum-chemical methods. Factors responsible for differences in chemiluminescence in the oxidation of organic substances with different polarities in the presence of the title compound were analyzed.     

Contribution to elucidation of the mechanism of preparation of 2-isobutyl-4-methyltetrahydro-2H-pyran-4-ol

Research on Chemical Intermediates - The effects of catalyst type (sulfuric acid, Amberlyst 15, p-toluenesulfonic acid, and p-dodecylbenzenesulfonic acid) and of addition of water on the...     

Notiz zur Darstellung von 4-Hydroxy-6-methyl-5,6-dihydro-2H-pyran-2-on

Meldrum's acid (2) is acylated by diketen affording the acylMeldrum's acid3. In aqueous bicarbonate its 3-oxogroup is selectively reduced by sodium tetrahydroborate giving the alcohol4, which readily undergoes cyclization in refluxing dioxane leading to the title pyrone7. Under identical conditions3 produces the pyrone6 with the pyrone carboxylic acid5 as intermediate.

     

Viscosity of aqueous solutions of 2-propyne-1-ol, 2-methyl-3-butyne-2-ol and 3-butene-2-ol

Viscosities of aqueous solutions of 2-propyne-1-ol (propargyl alcohol), 2-methyl-3-butyne-2-ol and 3-butene-2-ol have been measured at temperatures 308.15, 313.15, 318.15, 323.15 and 328.15?K over the entire composition range. Viscosity of the aqueous solutions of 2-methyl-3-butyne-2-ol and 3-butene-2-ol increases up to a maximum value and then starts decreasing almost linearly as the mole fraction of alcohol increases. 2-Methyl-3-butyne-2-ol + water and 3-butene-2-ol + water systems exhibit maxima around 0.5 and 0.2 mole fraction, respectively. Conversely, 2-propyne-1-ol + water system shows a rapid initial increase in viscosity up to 0.3 mole fraction followed by a slow steady increase as the mole fraction of alcohol increases to its pure state. Plots of excess viscosities against mole fraction of organic solutes for all the systems exhibit a sharp increase in η ^E to reach a well defined maxima, after which the curves show a descending trend. The variations of viscosity and excess viscosity with the composition of the mixtures have been interpreted in terms of hydrophobic and hydrophilic interactions between the species forming the mixtures.     

Concerning the products obtained from the condensation of 4-methyl-4-penten-2-ol with benzaldehyde

The products formed in the condensation reaction of4-methyl-4-penten-2-ol with benzaldehyde were reinvcstigated. Their constitutions and configurations were determined spectroscopically. For further characterisation, the three olefins 8–10 were epoxidised.     

Synthesis of bipyrazoles and pyrazoloisoxazoles from 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one

Phenylhydrazine or hydrazine react with 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one ( 1 ) to give 4-acetoacetyl-3-methylpyrazolin-5-ones 4 . The synthesis of bipyrazoles and pyrazoloisoxazoles from 4 are reported.     

Pyrones. II—the mass spectra and fragmentation mechanisms of methyl maltol (3-methoxy-2-methyl-4H-pyran-4-one) and methyl allomaltol (5-methoxy-2-methyl-4H-pyran-4-one)

The mass spectra of methyl maltol (3-methoxy-2-methyl-4H-pyran-4-one) and methylallomaltol (5-methoxy-2-methyl-4H-pyran-4-one) and a number of deuterium labelled analogues have been studied in detail. The two pyrones have common fragmentation pathways, all of which can be traced back to a primary rearrangement of the molecular ion. The loss of water from the molecular ion occurs by two processes, both involving the methoxymethyl protons. The loss of methyl from the molecular ion also occurs by two routes, only one of which involves the methoxy methyl protons directly.     

3-methylthio-1,2-dithiolylium salts : Reaction with 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxycoumarin

The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2$\text{H}$-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2$\text{H}$,5$\text{H}$-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2$\text{H}$-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2$\text{H}$-benzo [b]-pyran-2,4-diones.     

Multicomponent assembling of salicylaldehydes,malononitrile, and 4-hydroxy-6-methyl-2H-pyran-2-one: A fast and efficient approach to medicinally relevant 2-amino-4H-chromene scaffold

A new multicomponent reaction (MCR) was found: a sodium acetate-catalyzed transformation of salicylaldehydes, malononitrile and 4-hydroxy-6-methyl-2H-pyran-2-one in ethanol results in the fast (30 min) and efficient formation of new 4-pyrano-substituted 2-amino-4H-chromenes in 86–96% yields. The same transformation initiated by grinding in mortar in the presence of sodium acetate or potassium fluoride results in a faster (15 min) formation of 4-pyrano-substituted 2-amino-4H-chromenes in 80–90% yields. This novel ‘one-pot’ process opens an effective and convenient way to pyrano-functionalized 2-amino-4H-chromene systems, which are promising compounds for different biomedical applications.     

Peroxy and alkoxy radicals from 2-methyl-3-buten-2-ol

Quantum mechanical calculations were used to determine the structure and energetics of peroxy radicals (P1 and P2) and alkoxy radicals (A1-A3) formed in the atmospheric degradation of 2-methyl-3-buten-2-ol. At the level of theory employed (B3LYP/6-31G(d,p)) low energy conformers were identified with zero, one, or two hydrogen bonds. The beta C-C scission (decomposition) reactions are computed to occur with low barriers, and the 1,5 H-shift (isomerization) reaction of A2 is computed to be of negligible importance. Scission 2 of A2 is computed to be about 93% of the fate of A2, with the balance being scission 1. The new BB1K functional of Truhlar was employed to investigate activation barriers for single intramolecular H-atom transfers across the OH...O* hydrogen bonds, but the barriers to these reactions appear to be too high for these reactions to be important. Extensive searches for transition states for simultaneous double intramolecular H-atom transfer across OH...OH...O* hydrogen bond pairs were unsuccessful.     

Water-soluble heteroligand complexes of 2-methyl-4-oxo-4H-pyran-3-olatoneodymium(III) with amino acids

New water-soluble heteroligand complexes of 2-methyl-4-oxo-4H-pyran-3-olatoneodymium(III) with aliphatic amino acids (glycine, N-methylglycine, and alanine) have been prepared. Within the biological “transparency window” (700–900 nm) of their electronic absorption spectra, narrow bands of Nd³⁺ are found: ⁴F_7/2 ← ⁴I_9/2; ⁴F_5/2 ← ⁴I_9/2; ⁴F_3/2 ← ⁴I_9/2 (750, 810, and 880 nm). Such complexes can be used as markers for biological tissues visualization.     

Synthesis of 1,5-Disubstituted 3-(4-Hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-2-pyrazolines

Summary. A series of 1,5-disubstituted 3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-2-pyrazolines were synthesized by the reaction of α,β-unsaturated ketones derived from dehydroacetic acid and hydrazine in hot acetic acid or propionic acid. The structures of all new compounds were elucidated by microanalyses, ¹H and ¹³C NMR, IR, and mass spectroscopic measurements.