Functionalization at C-5 and at the C-6 methyl group of 4-methoxy-6-methyl-2-pyrone

A new entry to C-5 substituted 4-hydroxy-6-methyl-2-pyrones has been achieved. The best conditions to prepare the monobromo and the dibromo derivatives at C-3 and the C-6 methyl group of the title pyrone have been defined. The synthetic applicability of the phosphonium salts at CH₃-C-6 of both 4-methoxy-6-methyl-2-pyrone, 5 , and dehydroacetic acid, 2 , has also been evaluated.     

A study of the acylation of 4-hydroxy-6-methyl-2-pyrone and 4 hy(lroxy-6-phenyl-2-pyrone

The acylation of 4-hydroxy-6-melhyl-2-pyrone (1) and 4-hydroxy-6-phenyl-2-pyrone (XXII) with aliphatic acid anhydrides, or with aliphatic acid chlorides in trifluoroacetic acid, has been found to product; first the corresponding ester, which then rearranges, partially or wholly, depending on the conditions and on the nature of the acyl moiety, to form the corresponding 3-acylpyrone. With aromatic acid chlorides in pyridine or in trichloroacetic acid only the corresponding ester was obtained. These esters, however, could be rearranged to the corresponding 3-acylpyrones with aluminum chloride. Acetoaeetylation of 1 and 4-hydroxycoumarin (XXIX) with diketene gave, in both cases, the C-acetoacetylated product.     

Reaction of Aminobenzimidazoles with 4-Hydroxy-6-methyl-2-pyrone and 4-Hydroxycoumarine

6- and 7-(4-hydroxy-6-methyl-2-oxo-1-pyridyl)benzimidazoles and 1-(6- and 7-benzimidazolyl)-4-hydroxy-2-oxoquinolines were synthesized by reaction of aminobenzimidazoles with 4-hydroxy-6-methyl-2-pyrone and 4-hydroxycoumarine.     

New Condensation Products from 5,6-Dihydro-4-hydroxy-6-methyl-2-pyrone

We report the synthesis of new condensation products from 5,6-dihydro-4-hydroxy-6-methyl-2-pyrone, providing evidence for the particular reactivity of the 3 and 4 positions of this compound.     

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.     

Preparation of 7-ethoxy-3-hydroxy-6-methoxy-1-methyl-4-nitroisoquinoline

This paper reports the large scale preparation of 7-ethoxy-3-hydroxy-6-methoxy-1-methyl-4-nitroiso-quinoline (RWJ 19959, 2 ) from an available starting material, 4-ethoxy-3-methoxyphenylacetic acid ( 9 ). Previously 2 was prepared via a perchlorate salt which was found to decompose exothermically.     

The reactivity of 4-hydroxy-6-methyl-2-pyrone towards different types of ketones

4-Hydroxy-6-methyl-2-pyrone (triacetic acid lactone) reacts at C-3 with acetone, mesityl oxide and pentane-2,4-dione. The structures of the final products have been elucidated.     

Synthesis,halogenation, and nitration of 6-methyl-3-phenyl-2-pyrone derivatives

Simple methods for the synthesis of 3-aryl-6-methyl-2-pyrones and 3-aryl-5-carbalkoxy-6-methyl-2-pyrones by the reaction of ethyl -formylarylacetates with acetone and acetoacetic acid esters, respectively, are proposed. Some electrophilic substitution reactions of 6-methyl-3-phenyl-2-pyrone and 5-carbethoxy-6-methyl-3-phenyl-2-pyrone were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1477–1480, November, 1985.     

Hydrogen bonds in dimers of 3-hydroxy-2-methyl-4-pyrone. AIM analysis

According to quantum topological analysis performed at the MP2/6-311++G** level the intramolecular hydrogen bond OH⋯O=C in 3-hydroxy-2-methyl-4-pyrone (maltol) is weak and has ionic nature. This bond is broken upon formation of H-complex of maltol with phosgene and with increase the polarity of medium. The chain dimer of maltol is stabilized by weak intermolecular bonds OH⋯O=C and CH⋯O=C of ionic character, whereas the cyclic dimer by two medium in strength intermolecular hydrogen bonds OH⋯O=C. Original Russian Text ? E.P. Doronina, T.N. Aksamentova, N.N. Chipanina, S.A. Mukha, S.A. Medvedeva, 2009, published in Zhurnal Obshchei Khimii, 2009, vol. 79, No. 2, pp. 308–313.     

Platinum(II) complexes with 9,10-phenanthraquinone and 3-hydroxy-2-methyl-4-pyrone

Conclusions The Pt(II) complexes with 9,10-phenanthraquinone and 3-hydroxy-2-methyl-4-pyrone were obtained and characterized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 900–902, April, 1981.     

Vilsmeier formylation of 2-methyl-3 -carbethoxy-5-methoxy- and 2-methyl-5-methoxyindoles

The corresponding 6- and 3-formyl derivatives were obtained by formylation of 2-methyl-3-carbethoxy-5-methoxy- and 2-methyl-5-methoxyindole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 339–341, March, 1971.