Ring size effects on the gas phase protonation of cyclic ketones

Experimental proton affinities of cyclic ketones are determined showing evidence for a larger strain energy in protonated vs. neutral cyclic ketones.     

Interrupted energy transfer: highly selective detection of cyclic ketones in the vapor phase

We detail our efforts toward the selective detection of cyclic ketones, e.g. cyclohexanone, a component of plasticized explosives. Thin films comprised of a conjugated polymer are used to amplify the emission of an emissive receptor via energy transfer. We propose that the energy transfer is dominated by an electron-exchange mechanism to an upper excited state of the fluorophore followed by relaxation and emission to account for the efficient energy transfer in the absence of appreciable spectral overlap. Exposure to cyclic ketones results in a ratiometric fluorescence response. The thin films show orthogonal responses when exposed to cyclic ketones versus acyclic ketones. We demonstrate that the exquisite selectivity is the result of a subtle balance between receptor design and the partition coefficient of molecules into the polymer matrix.     

New method for the ring enlargement of cyclic ketones

A simple two step procedure which allows thering enlargement of cyclic ketones is disclosed which takes advantage of the high nucleophilicity of α-selenoalkyllithiums towards carbonyl compounds and of a novel transposition reaction which occurs on the resulting β-hydroxyselenides.     

Synthesis of cyclic enones via direct palladium-catalyzed aerobic dehydrogenation of ketones

α,β-Unsaturated carbonyl compounds are versatile intermediates in the synthesis of pharmaceuticals and biologically active compounds. Here, we report the discovery and application of Pd(DMSO)(2)(TFA)(2) as a catalyst for direct dehydrogenation of cyclohexanones and other cyclic ketones to the corresponding enones, using O(2) as the oxidant. The substrate scope includes heterocyclic ketones and several natural-product precursors.     

Gold-catalyzed intramolecular carbocyclization of alkynyl ketones leading to highly substituted cyclic enones

The reaction of the internal alkynyl ketones 1 (n=1) under the combined catalyst, AuCl3 and AgSbF6, gave the enones 2 in good to high yields, whereas that of the terminal alkynyl ketones 1 (n=0) under the combined catalyst, AuCl3 and AgOTf, afforded the cyclic enones 3.     

Potential anticonvulsants. III. The condensation of isatin with cyclic ketones

Isatin has been condensed with a series of cyclic ketones to give 3-substituted-3-hydroxyoxindoles as potential anticonvulsant agents.     

Intercalation of cyclic ketones into vanadyl phosphate

Intercalation compounds of vanadyl phosphate with cyclic ketones (cyclopentanone, cyclohexanone, 4-methylcyclohexanone, and 1,4-cyclohexanedione) were prepared from corresponding propanol or ethanol intercalates by a molecular exchange. The intercalates prepared were characterized using powder X-ray diffraction and thermogravimetric analysis. The intercalates are stable in dry environment and decompose slowly in humid air. Infrared and Raman spectra indicate that carbonyl oxygens of the guest molecules are coordinated to the vanadium atoms of the host layers. The local structure and interactions in the cyclopentanone intercalate have been suggested on the basis of quantum chemical calculations.     

Enantioselective inclusion in bile acids: resolution of cyclic ketones

Cholic and deoxycholic acids were found to form inclusion compounds with various racemic cyclic ketones enabling direct and straightforward enantiomer separation. The X-ray structure of the 2:1 inclusion complex between (−)-bicyclo[3.2.0]-hept-2-en-6-one and cholic acid is reported.     

Regiochemical studies of the ring expansion reactions of hydroxy azides with cyclic ketones

The regiochemistry of ring expansions of 2-substituted cyclic ketones using 1,2-azidoethanol and 1,3-azidopropanol was examined. It was determined that the reactions of ketones with an adjacent methyl or ethyl group are generally unselective, but that bulkier substituents lead to preferential migration of the more highly substituted carbon. In addition, it was found that ketones bearing inductively electron-withdrawing substituents (OMe, Ph, Br) undergo selective migration of the less highly substituted carbon. For some substrates, alternative reaction pathways were also identified.     

Baeyer-Villiger oxidation of cyclic ketones over iron-containing mesoporous MCM-48 silica materials

Fe-MCM-48 mesoporous material was found to be a highly active catalyst for the Baeyer-Villiger oxidation of several cyclic ketones. The catalyst could be reused several times without any loss of activity.     

Catalyst-free synthesis of amines from cyclic ketones and formamides in superheated water

A novel and environmentally benign protocol for the synthesis of amines from cyclic ketones and formamides is demonstrated. The reaction proceeds under catalyst-free and superheated water conditions and yields range from poor to excellent.     

Synthesis of 2,3-polymethylenepyridines from 3-aminoacrolein and cyclic ketones

It is shown that the reaction of 3-aminoacrolein with cyclic ketones of medium size can be used to synthesize inaccessible 2,3-polymethylenepyridines with polymethylene chains of 5, 6, 10, and 12 carbon atoms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1649–1651, December, 1986.     

A versatile synthesis of retinoids via condensation of the side-chain to cyclic ketones

A simple synthesis of ethyl 3,7-dimethyl-2,4,6-nonatriene-8-ynoates and their corresponding alcohols is presented; codensation with various cyclic ketones can lead to retinoids having modified ring structures.     

Stereochemical evidence for single electron transfer mechanism in the reduction of cyclic ketones with alkoxyaluminium dichlorides

The stereochemical results of the reduction of cyclic ketones with alkoxyaluminium dichlorides do not conform to the conventional polar cyclic mechanism and may be explained by a single electron transfer mechanism.     

A novel aromatic alkylation of anilines with cyclic and acyclic ketones under hydrothermal conditions

A novel aromatic ring-alkylation was achieved by condensation between aniline·HCl salts and cyclic or acyclic ketones under hydrothermal conditions.     

Beyond the corey reaction: one-step diolefination of cyclic ketones

The reactivities of the cyclic ketones cycloheptanone, cyclodecanone, and cycloundecanone with dimethylsulfoxonium methylide generated from trimethylsulfoxonium iodide and base (NaH) were studied in diglyme at 130 degrees C. Oxiranes, which primarily form via the Corey reaction, lead to ring expansions to give oxetanes and oxacyclopentanes when an excess of dimethylsulfoxonium methylide is used. The Corey reaction is suppressed in the presence of excess of base, and 1,3-terminal dienes form instead (we term this reaction the Yurchenko diolefination). Our mechanistic proposal involves the deprotonation of the betaine that forms after the attack of dimethylsulfoxonium methylide on the carbonyl group of the ketone. The key step of the diolefination reaction involves a [2,3]-sigmatropic rearrangement of the ylide to a gamma-unsaturated sulfoxide with a barrier of 9.9 kcal/mol (DeltaH298, MP2/cc-pVDZ, for the cycloheptane derivative). The elimination of sulfenic acid from the gamma-unsaturated sulfoxide in the terminal step of the diolefination is associated with a higher barrier (17.3 kcal/mol) but is strongly accelerated in the presence of base. The reactivity of cyclic ketones in the Yurchenko reaction depends on the ring size; medium-sized cyclodecanone is less reactive than either cycloheptanone or cyclododecanone.     

Novel three-component tandem reactions of cyclic mono ketones, isatin and sarcosine: formation of dispiropyrrolidines

One-pot, three-component tandem reactions of cyclic mono ketones, isatin and sarcosine affording dispiropyrrolidines stereoselectively are reported for the first time.     

A comparative study on aldol‐type condensation reactions of cyclic,acyclic and substituted cyclic ketones by the W(CO)6/CCl4/UV system

Aldol‐type condensation reactions of a number of cyclic, acyclic and substituted cyclic ketones were investigated using the W(CO)₆/CCl₄/UV system. The progress of the reactions was followed by IR and GC‐MS techniques. The cyclic ketone derivatives with β‐ and γ‐substituent gave the expected condensation products. However, the α‐substituted cyclic, acyclic and unsubstituted cyclic ketones with rings larger than six did not. Formation of [W]–ketone complexes with all of the ketones used was observed by FTIR. With respect to our studies, a mechanism involving an intermediate seven‐coordinate tungsten complex has been proposed. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of geminal bisphosphonates via organocatalyzed enantioselective Michael additions of cyclic ketones and 4-piperidones

A Michael addition reaction of cyclic ketones and piperidones to a vinyl phosphonate is described. The reaction, catalyzed by chiral diamines, produced geminal γ-oxobisphosphonates in high yields (up to 92%) and very high ees (up to >99%). Disubstituted ketones gave drs of up to 8?:?92. The synthesis and characterization of several new compounds with potential biological activity is described.     

A novel synthesis of cyclic α-amino aldehydes, amino alcohols, and α-amino acid methyl esters from cyclic ketones through sulfinylaziridines

Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from cyclic ketones and chloromethyl p-tolyl sulfoxide in three steps in good yields, with N-lithio arylamines gave sulfinylaziridines in high yields. On treatment with N-lithio aniline or N-lithio p-chloroaniline, the sulfinylaziridines gave α-amino aldehydes in high yields. The α-amino aldehydes were converted to amino alcohols and α-amino acid methyl esters in moderate to good yields. This procedure offers an efficient method for synthesis of cyclic α-quaternary α-amino aldehydes, amino alcohols, and α-amino acid derivatives from cyclic ketones.