Spectrophotometric determination of selenium(IV) with 5,5-dimethyl-1,3-cyclohexanedione

5,5-Dimethyl-1,3-cyclohexanedione (dimedone) reacts in acid aqueous solution with selenium(IV) to give a benzoxaselenol which has an absorption maximum at 313 nm with a molar absorptivity of 4.00 x 10(3) l.mole(-1).cm(-1). The compound is extractable into chloroform, to give a solution with an absorption maximum at 300 nm with a molar absorptivity of 3.77 x 10(3) l.mole(-1).cm(-1). The calibration graph is linear up to 30 ppm selenium, with a detection limit of 0.1 ppm in the final solutions. Of the various other ions tested, only iron(III) interferes at all concentrations but the addition of 1000 ppm fluoride will mask 50 ppm Fe(3+). The method has good reproducibility, with a relative standard deviation of 1.0% for pure solutions. The method has been applied to the analysis of fire-refined copper.     

2-Aryl-7,7-dimethyl-5,6,7,8-tetrahydrothieno[3,2-c]azepin-4-ones from 5,5-dimethyl-1,3-cyclohexanedione

A novel synthesis of substituted thieno[3,2-c]azepinones is described. This new approach uses 5,5-dimethyl-1,3-cyclohexanedione (dimedone) as the starting material. Oxime intermediates are obtained in three steps from the aforementioned diketone. Using these intermediates, the title compounds are synthesized in moderate yields.     

Spectrophotometric determination of periodate and glycerol with 5,5-dimethyl-1,3-cyclohexanedione bisthiosemicarbazone monohydrochloride

A direct spectrophotometric method for the determination of periodate (1—10 ppm) is based on the formation of a yellow oxidation product of 5,5-dimethyl-1,3-cyclohexanedione bisthiosemicarbazone monohydrochloride in aqueous solution at pH 0.5—1.2. The molar absorptivity at 415 nm is 1.72 × 10⁴ l mol^-1 cm^-1. The relative standard deviation is 0.8% for 8.0 ppm periodate. A modification to this procedure is used for the indirect spectrophotometric determination of glycerol (2–10 ppm), via the Malaprade reaction.     

Microwave—prompted Reaction of Cinnamonitrile Derivatives with 5,5—Dimethyl—1,3—cyclohexanedione

In the reactions of α-cyanocinnamonitrile or β-cyano-β-carbothoxy styrene with 5,5-dimethyl-1,3-cyclohexanedione in the presence of ammonium acetate under microwave irradiation without solvent,the 2-amino-5,6,7,8-tetrahydro-5-oxo-4-aryl-7,7-dimethyl-4H-benzo-[b]-pyran derivatives were obtained.However,in the reactions of arylidenecyanoacetamide with 5,5-dimethyl-1,3-cyclohexanedione under the same reaction conditions,the acridine derivatives were obtained.The structures of the products were determined by single crystal X-ray diffraction analysis.     

环状碳酸酯5,5-二甲基-1,3-二噁烷-2-酮的合成

在三乙胺存在下,2,2-二甲基-1,3-丙二醇和氯甲酸乙酯反应合成了环状碳酸酯5,5-二甲基-1,3-二噁烷-2-酮,其结构经1H NMR和IR表征。提出了可能的反应机理。     

Anthocyanidins and related compounds—VIII Condensation reactions of flavylium salts with 5,5-dimethyl-1,3-cyclohexanedione in acid solutions

4′-Hydroxyflavylium salts, unsubstituted at position 3, react with 5,5-dimethyl-1,3-cyclohexanedione in acid solutions to yield para-hydroxyphenacyl-5-keto-tetrahydroxanthene derivatives, e.g., Va, isomeric with the flavan derivatives, e.g., IIa, formed at pH 5·8. These flavans isomerize to the tetrahydroxanthenes in both acid and alkaline media.

7-Hydroxy- and 3-methyl-4′-hydroxyflavylium salts yield flavan derivatives, eq. IIIa, IId, when condensed either in acid solutions or at pH 5·8. Isomerization of these flavans to corresponding tetrahydroxyanthenes has not been detected.     

Conformation of 5,5-disubstituted 2,2-dimethyl-1,3-dioxanes

It was established by PMR spectral data that in solutions of derivatives of 5-acetoxymethyl-, 5-methyl-, and 5-hydroxymethyl-2,2-dimethyl-1,3-dioxanes with nitrogen-containing substituents (2,4-disubstituted 1,3,5-triazin-6-ylamino, benzamido, and nitro groups) with an N-C₍₅₎ bond the 1,3-dioxane ring exists in the chair conformation with primarily an axial orientation of the nitrogen-containing substituent. Depending on the nature of the substituents attached to the C₍₅₎ atom, the 1,3-dioxane ring may exist either in the stable chair conformation or may undergo rapid inversion of the chair-chair type at 20 °C.The author sincerely thanks A. I. Kol'tsov for his assistance in recording and interpreting the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 468–473, April, 1985.     

Cationic copolymerization of 2-methylene-5,5-dimethyl-1,3-dioxane with 2-methylene-1,3-dioxolane and 2-methylene-1,3-dioxane

Copolymers of the cyclic ketene acetals, 2-methylene-5,5-dimethyl-1,3-dioxane, 3 , (M₁) with 2-methylene-1,3-dioxolane, 4 , (M₂) or 2-methylene-1,3-dioxane, 5 , (M₂), were synthesized by cationic copolymerization. An experimental method was designed to study the reactivity of these very reactive and extremely acid sensitive cyclic ketene acetal monomers. The reactivity ratios, calculated using a computer program based on a nonlinear minimization algorithm, were r₁ = 6.36 and r₂ = 1.25 for the copolymerization of 3 with 4 , and r₁ = 1.56 and r₂ = 1.42 for the copolymerization of 3 with 5. FTIR and ¹H-NMR spectra when combined with the values of r₁ and r₂ showed that these copolymers were formed by a cationic 1,2-polymerization (ring-retained) route. Furthermore the tendency existed to form very short blocks of M₁ or M₂ within the copolymers. Cationic copolymerization of cyclic ketene acetals have the potential to be used for synthesis of novel polymers. © 1996 John Wiley & Sons, Inc.     

不需加催化剂在纯水相介质中进行芳香醛与5,5-二甲基-1,3-环己二酮的缩合反应

在纯水相中,不另加任何催化剂可以十分方便、有效地通过芳香醛与5,5-二甲基-1,3-环己二酮间的缩合反应合成氧杂葸二酮类衍生物.该反应只需在热水中搅拌下即可有效进行.而且这种方法具有明显的环境友好、高产率和操作过程简便的优点.     

Homolytic telomerization of vinyltrimethylsilane with 5,5-dimethyl-1,3-dioxane

The homolytic telomerization of vinyltrimethylsilane by 5,5-dimethyl-1,3-dioxane follows three principal routes, with the formation of 2- and 4-substituted 5,5-dimethyl-1, 3-dioxanes and a formate ester. The rings in the reaction products (2-trimethylsilylethyl- and 4-trimethylsilylethyl-5,5-dimethyl-1,3-dioxane) exist in the chair conformation. The substituants in the 2- and 4-positions of the dioxane ring occupy equatorial positions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1031–1035, August, 1986.