Alkylaromatic Ketones Research Articles

Characterization of Substituted 1,3-Dioxolanes and 1,3-Dioxanes by Gas Chromatography–Mass Spectrometry

Until recently, one of the reasons for the unsatisfactory characterization of alicyclic ketals of aliphatic and alkylaromatic ketones was the absence of any mention of the presence of such compounds in natural samples. Another reason is in the low yields of such ketals on the interaction of ketones and diols under the conditions of conventional acid catalysis. To optimize the synthesis of trace amounts of such ketals, we used cobalt(II) bromide and dimethyl glyoxime as catalysts. The simplest chromatographic parameters, including the difference between the retention indices of the products and the starting compounds (difference in retention indices, DRI), are effective for identifying the target ketals in reaction mixtures. Such combined chromatography–mass spectrometric characteristics as homologous increments of retention indices (iRI) are informative not only for the group identification of analytes (assignment to the corresponding homologous series) and the assessment of their molecular weights (at low-intense signals of molecular ions). They are also useful for the determination of the total number of branches of the sp3-carbon skeleton of molecules (N) using the regression of N ≈ aiRI + b.

Green oxidation of alkylaromatics using molecular oxygen over mesoporous manganese silicate catalysts.

A very green catalytic method has been introduced for the synthesis of alkylaromatic ketones by solvent-free benzylic oxidation of alkylaromatics with molecular oxygen (O2) over hexagonally mesostructured MnSBA-15 catalysts synthesized with a variety of manganese (Mn) contents using a pH-adjusting direct hydrothermal (pH-aDH) method. For example, the solvent-free oxidation of ethylbenzene (EB) over different mesoporous MnSBA-15 catalysts and uniform pore sized MnMCM-41(31) prepared by an alkaline hydrothermal method has been systematically evaluated. Washed MnSBA-15(4) (W-MnSBA-15(4)) or green mesoporous MnSBA-15(4) obtained after the removal of the non-framework octahedral Mn2O3 species deposited on the active surface of MnSBA-15(4) using a promising chemical treatment method is used for this reaction to evaluate its catalytic activity. Meanwhile the recyclability and hot-filtration experiments for this reaction have been also studied. The catalytic activities obtained from the above catalytic results prove that the W-MnSBA-15(4) has higher EB conversion and AP[double bond, length as m-dash]O selectivity than the other mesoporous catalysts used in this reaction. Therefore, in order to find the optimal reaction parameters for this reaction, various reaction parameters with W-MnSBA-15(4) have been thoroughly evaluated. Using W-MnSBA-15(4), the catalytic results obtained with different oxidants used in this reaction have also been discussed clearly. The catalytic results of solvent-free benzylic oxidations with W-MnSBA-15(4) conducted with different alkylaromatic molecules have been obviously discussed. All the mesoporous catalysts used in this reaction have been characterized using several instrumental techniques to confirm them as the standard mesoporous catalysts. The plausible reaction mechanism for the solvent-free oxidation of EB has been successfully reported based on the characterization results of the catalyst and catalytic results. The ESR and UV-vis DRS results of the W-MnSBA-15 catalyst used in these reactions corroborate that the disordered octahedral divalent (Mn2+) and tetrahedral trivalent (Mn3+)-species have been successfully incorporated on the silica surface of the catalysts. Based on the catalytic results, it is noteworthy to observe that mesoporous W-MnSBA-15(4) is a highly active, green and promising heterogeneous catalyst for the selective synthesis of alkylaromatic ketones, since the catalyst produces the best catalytic activity among the other mesoporous Mn silicate catalysts.

The Fischer Reaction in the Synthesis of 2,3-Disubstituted 7-Azaindoles*

We present the results of our study towards the synthesis of 2,3-disubstituted 7-azaindoles by cyclization of 2-pyridylhydrazones of aliphatic and alkylaromatic ketones under the conditions of Fischer reaction, catalyzed by polyphosphoric acid.

Photochemical studies on acyclic alkyl aromatic ketones in the solid state: asymmetric induction and increased chemoselectivity

The acyclic alkyl aromatic ketones, 2-isobutyl-4-methyl-1-arylpentan-1-one derivatives were designed and synthesized for photochemical investigations. Irradiation of such compounds in acetonitrile solution led to the Yang cyclization and Norrish type II cleavage photoproducts with a ratio of 1:1, whereas the reaction conducted in the solid state using the ionic chiral auxiliary method led to only the Yang cyclization product with as high as 99% ee. Furthermore, the conformational transitions were first observed in the reaction.

Highly active mesoporous chromium silicate catalysts in side-chain oxidation of alkylaromatics

We approach a green method in the production of alkylaromatic ketones over hexagonally ordered mesoporous CrSBA-15 catalysts, which were used, in green routes, in the liquid-phase oxidation of alkylaromatics. A promising chemical treatment method was used with ammonium acetate solution to remove the toxic nature of non-framework chromium oxides deposited on the surface of calcined CrSBA-15(8), and the obtained green mesoporous CrSBA-15(8) catalyst was used to find its catalytic activity while the recyclability of mesoporous CrSBA-15 catalysts was also studied. Particularly, the mesoporous CrSBA-15 catalysts synthesized with a variety of chromium contents were extensively used in the production of acetophenone (AP=O) with various reaction parameters. On the basis of all catalytic results, the mesoporous CrSBA-15(8) catalyst produced a higher selectivity of alkylaromatic ketones (76-100%) as compared to other CrSBA-15 catalysts and was found to be a highly active, recyclable and promising heterogeneous catalyst for selective synthesis of alkylaromatic ketones.

New chiral borohydrides. 3. Preparation and asymmetric reducing properties of potassium 9- O -(1,2-isopropylidene-5-deoxy-α-D-xylofuranosyl)-9-borata-bicyclo[3.3.1]nonane

A stable, new chiral borohydride, potassium 9- O- (1,2- O-isopropylidene-5- deoxy-α-D-xylofuranosyl)-9-boratabicyclo[3.3.1]nonane (K xylide, 1D) using a xylose derivative as a chiral auxiliary was prepared by the treatment of the corresponding borinic ester 3D with potassium hydride in THF. The reagent provided high optical induction for asymmetric reduction of prochiral ketones, such as relatively hindered ketones, alkyl aromatic ketones, and α-haloketones. Thus, the reduction of 4-methyl-2-pentanone, 3,3-dimethyl-2-butanone, and 2,2-dimethylcyclopentanone provided the corresponding alcohols m 65 % ee, 76 %ee, and 80 % ee, respectively. The optical induction for unhindered aliphatic ketones was low, such as 36 % ee for 2-heptanone, 46 % ee for 3-methyl-2-butanone. The reductions of alkyl aromatic ketones provide high optical inductions, such as 70 % ee for acetophenone, 82 % ee for butyrophenone, 89 % ee for isobutyrophenone, 99 % ee for pivalophenone, and 93 % ee for 2′-methylacetophenone. For some functionalized ketones, the reduction of 2-chloroacetophenone yields the corresponding alcohol in 92% ee, whereas the reduction of 3-acetylpyridine, methyl benzoylformate, and 4-phenyl-3-butyn-2-one provide the corresponding alcohols in 62% ee, 60 % ee and 52 % ee, respectively.

The separation of alkyl aromatic ketones by means of thin-layer chromatography

The separation of alkyl aromatic ketones by means of thin-layer chromatography