Yu. Kh. Sazhneva

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%).

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-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.

Synthesis of 6-hetaryl-5,5-dialkyl-3,3-dimethyl-tetrahydropyran-2,4-diones by Reformatsky Reaction

Zinc enolates derived from ethyl 4-bromo-2,2,4-trimethyl-3-oxopentanoate and 4-bromo-4- ethyl-2,2-dimethyl-3-oxohexanoate react with 2-furan-, 2-thiophene-, 1-(3-nitrophenyl)-2-pyrrole-, 1-acyl-3-indole-, and 2-pyridinecarbaldehydes to give the corresponding 6-hetaryl-5,5-dialkyl-3,3-dimethyltetrahydropyran-2,4-diones.

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.

Alkylation with Substituted Phenacyl Bromides of Sodium Enolates from 6-Aryl-3,5,5-trimethyl-2,3,5,6-tetrahydropyran-2,4-diones

We have established formerly that reaction of ethyl 2,4-dibromo-2,4-dimethyl-3-oxopentanoate with zinc and aromatic aldehydes gives rise to previously unknown 6-aryl-3,5,5-trimethyl-2,3,5,6-tetrahydropyran-2,4-diones [1]. It is known that tetrahydropyrandiones with substituents in 3-position containing a carbonyl group possess various kinds of biological activity [234]. Aiming at preparation of new tetrahydropyrandiones types with aroylmethyl group in 3-position of the pyran ring we studied reactions between sodium enolates (II) obtained from 6-aryl3,5,5-trimethyl-2,3,5,6-tetrahydropyran-2,4-diones (I) and para-substituted phenacyl bromides. The investigation established that the reaction between these compounds occurred readily in anhydrous DMSO yielding C-alkylation products of sodium enolates IIa3c, 6-aryl-3-aroylmethyl-3,5,5-trimethyl2,3,5,6-tetrahydropyran-2,4-diones (IIIa3j).

Reaction of ethyl 2,4-dibromo-2,4-dimethyl-3-oxopentanoate with zinc and aldehydes

Ethyl 2,4-dibromo-2,4-dimethyl-3-oxopentanoate reacts with zinc and aliphatic or aromatic aldehydes to furnish 3,5,5-trimethyl-6-R-2,3,5,6-tetrahydropyran-2,4-diones as a single geometrical isomer that in polar solvents converts into enol form.