Reaction of Zinc and Sodium Enolates of 3-Alkyl-6-aryl-5,5-dimethyl-2,3,5,6-tetrahydropyrane-2,4-diones with Acyl Chlorides or Benzyl Bromides

Zinc enolates of 3-alkyl-6-aryl-5,5-dimethyl-2,3,5,6-tetrahydropyrane-2,4-diones react with acyl chlorides to form O-acylation products, 4-acyloxy-3-alkyl-6-aryl-5,5-dimethyl-5,6-dihydropyrane-2-ones. Sodium enolates of these pyranediones react in DMSO with substituted benzyl bromides to give mainly C-alkylation products, 3-alkyl-6-aryl-3-(4-R-benzyl)-5,5-dimethyl-2,3,5,6-tetrahydropyrane-2,4-diones, as single geometric isomers. In some cases, O-alkylation products, 4-alkoxy-3-alkyl-6-aryl-5,5-dimethyl-5,6-dihydropyrane-2-ones, are formed as by-products (10-15%).     

Reaction of Zinc Enolates of Alkyl Esters of Substituted 4-Bromo-3-Oxoalkanoic Acids with Aldehydes

Zinc enolates formed from ethyl 4-bromo-2,2,4-trimethyl-3-oxopentanoate react under the conditions of one- of two-stage synthesis with aliphatic, unsaturated, or aromatic aldehydes to form 6-R-2,2,4,4-tetramethyl-2,3,5,6-tetrahydropyran-2,4-diones. Zinc enolates obtained from ethyl 4-bromo-2,2-dimethyl-3-oxopentanoate, -hexanoate, and -2,2,5-trimethyl-3-oxohexanoate under the similar conditions react with aliphatic or aromatic aldehydes to give mainly 5-R¹-6-R²-3,3-dimethyl-2,3,5,6-tetrahydropyran-2,4-diones as E or Z isomers or their mixtures. Zinc enolates generated from the ethyl 4-bromo-2,2-diethyl- or 2-benzyl-2-ethyl-3-oxobutanoates react with aromatic aldehydes to give ethyl 5-R-2-R-2-ethyl-3-oxo-4-pentenoates as E isomers.     

Reactions of Sodium Enolates Derived from 6-Aryl-3,5,5-trimethyl-2,3,5,6-tetrahydropyrane-2,4-diones with Substituted Benzenesulfonyl Chlorides and Arenediazonium Salts

Sodium enolates derived from 6-aryl-3,5,5-trimethyl-2,3,5,6-tetrahydropyrane-2,4-diones react with substituted benzenesulfonyl chlorides to give the corresponding O-sulfonation products, 6-aryl-4-(4-R-phenylsulfonyloxy)-3,5,5-trimethyl-5,6-dihydropyrane-2-ones. Reactions of the title compounds with arenediazonium tetrafluoroborates afford 6-aryl-3-arylazo-3,5,5-trimethyl-2,3,5,6-tetrahydropyran-2,4-diones as mixtures of syn and anti isomers.     

Synthesis of 6-Aryl-3,3-dimethyl-5-phenyl-2,3,5,6-tetrahydropyran-2,4-diones

Zinc enolates obtained from methyl 4-bromo-2,2-dimethyl-3-oxo-4-phenylbutanoates and zinc react with aromatic aldehydes to form 6-aryl-3,3-dimethyl-5-phenyl-2,3,5,6-tetrahydropyran-2,4-diones as a single geometric isomer.     

Synthesis,Structure, and Keto-Enol Tautomerism of 3-R<Superscript>1</Superscript>-5,5-R<Superscript>2</Superscript>,R<Superscript>2</Superscript>-6-R<Superscript>3</Superscript>-2,3,5,6-Tetrahydropyran-2,4-diones

Ethyl esters of 2,4-dibromo-2-R¹-4-R²-3-oxopentanoic and -hexanoic acids react with zinc and aliphatic or aromatic aldehydes under the conditions of the Reformatskii reaction to give 3-R¹-5,5-R², R²-6-R³-2,3,5,6-tetrahydropyran-2,4-diones, which are obtained in three forms: keto, enol with enolization of the keto group, and enol with enolization of the ester group. The keto form is isolated by crystallization from a mixture of CCl₄ and petroleum ether; the first enol form, from MeOH, EtOH, and polar aprotic solvents; and the second enol form, from CHCl₃. The second enol form is oxidized in DMSO to form a keto compound containing a hydroxy group at the 3-position of the heteroring.     

Parameters of Li2O2 · H2O crystallization from the LiOH-H2O2-H2O ternary system

The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H₂O₂-H₂O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li₂O₂ · H₂O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li₂O₂ · H₂O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis.     

Kinetics and mechanism of decomposition of peroxide compounds in the liquid phase of the KOH-H<Subscript>2</Subscript>O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O system in vessels made of various materials

Decomposition kinetics of peroxide compounds in the liquid phase of the system KOH-H₂O₂-H₂O at an initial hydrogen peroxide concentration of about 14.5 M and pH 12.7 in vessels made of Pyrex glass, polyethylene terephthalate, and 12Kh18N10T steel was studied in the temperature range from ?10 to +50°C. The main kinetic parameters of the processes under study were determined. The influence exerted by the material of the reaction vessel on the kinetics and mechanism of decomposition of peroxide compounds in the liquid phase of the system under study were determined.     

Synthesis of 6-Aroyl-3,3,5,5-tetramethyl-2,3,5,6-tetrahydropyran-2,4-diones and Their Reaction with Phenylhydrazine

Methyl 4-bromo-3-oxo-2,2,4-trimethylpentanoate reacts with zinc and arylglyoxals yielding 6-aroyl-3,3,5,5-tetramethyl-2,3,5,6-tetrahydropyran-2,4-diones. The latter with phenylhydrazine afford 6-(1-aryl-2-phenylhydrazonomethyl)-3,3,5,5-tetramethyl-2,3,5,6-tetrahydropyran-2,4-diones.