Original method for the ring enlargement of cyclic ketones

Thallium ethoxide in chloroform was found to be a particularly valuable combination for the rearrangement of β-hydroxyselenides to ketones.     

New methylene homologation method for cyclic ketones

Teaching new tricks to an old dog: By intercepting adducts between ketones and lithium trimethylsilyldiazomethane, a new Tiffeneau-Demjanov type methylene homologation could be realized in a single-step operation. Among proton sources and Lewis acids, silica gel was found to be the most effective reagent for the protonation of intermediates and their subsequent ring expansion.     

A direct retro-Reformatsky fragmentation: formal ring enlargement of cyclic ketones for novel and practical synthesis of heterocyclic enamines

A novel and practical synthesis of heterocyclic enamines has been developed from the formal ring enlargement of cyclic ketones, which comprised the retro-Reformatsky fragmentation reaction as a key step. Under alkaline bromination conditions, the Reformatsky adducts derived from five- to seven-membered cyclic ketones underwent efficiently a direct retro-Reformatsky fragmentation, followed by spontaneous alpha,alpha-dibromination, to produce alpha,alpha,omega-tribromo-beta-ketoester compounds in a one-pot reaction. Highly regioselective reduction of alpha,alpha,omega-tribromo-beta-ketoesters with Cu-Zn alloy under mild conditions afforded omega-bromo-beta-ketoesters in good to excellent yields. Treatment of omega-bromo-beta-ketoesters with sodium azide followed by intramolecular aza-Wittig reaction or catalytic hydrogenation furnished heterocyclic secondary enamines, while a straightforward cyclocondensation of omega-bromo-beta-ketoesters with amines led to the formation of heterocyclic tertiary enamines.     

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.     

An efficient method for the synthesis of alkylidenecyclobutanones by gold-catalyzed oxidative ring enlargement of vinylidenecyclopropanes

Rings of gold: Vinylidenecyclopropanes can undergo efficient oxidative ring enlargements under mild conditions to give the corresponding alkylidenecyclobutanone derivatives in good yields. A plausible mechanism for this transformation has been proposed, and a new Au(I) -N complex, which can be used as an efficient catalyst in this oxidation reaction, has been isolated.     

Formation of spiro ketolactones versus alkoxy radical fragmentation-promoted three-atom ring enlarged lactones from cyclic ketones

A dual pathway from readily available 2-allyl-2-carboethoxycycloalkanones 1 provides a new facile stereoselective synthesis either of functionalized spiro ketolactones 4 or of ring enlarged lactones 7 in one-step. Thus, iodination of 5-8-membered 2-allyl-2-carboethoxycycloalkanones 1a-d led, in excellent yields, to spiro ketolactones 4a-d, respectively, as single stereoisomers. On the other hand, iodination of 1a-d under alkoxy radical fragmentation conditions via incipient hemiketals produced the 8-, 9-, 10-, or 11-membered, three-atom ring enlarged, poly-functionalized lactones 7a-c as two stereoisomers and 8 as a single isomer.     

Novel ring enlargement of 1-aminopyrrolidines

1-Aminopyrrolidines undergo oxidative ring enlargement to 1,4,5,6-tetrahydropyridazines on treatment with silica gel in chloroform-methanol.     

Carbenoid type base induced ring expansion of the adducts of cyclic ketones with bis(phenylthio)methyllithium

In another application of the principle that metallo derivatives of bis(phenylthio)acetals behave as carbenoids when present in the same molecule with another anionic group, the adducts of cyclic ketones with bis(phenylthio)methyllithium react with an alkyllithium to yield the ring expanded α-(phenylthio) ketones.     

New method of constructing the 1-pyrazoline ring

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, p. 1697, December, 1989.     

Reaction of cyclic ketones with KOH-DMSO

Upon reaction of cycloalkanones with a KOH-DMSO system 2-methylenecycloal-kanols are formed, the yield (10–37%) of which decreases in the series: cyclohexanone > cycloheptanone > cyclooctanone > cyclododecanone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1601–1605, July, 1990.     

Isomerization recyclization of pyridylethylated ketones. New method for the synthesis of quinoline derivatives

Quinolines and 1,2,3,4-tetrahydroquinolines were obtained by heating quaternary salts of pyridylethylated ketones with sulfites of primary amines in an ampul. 1-Tetralone or substituted 2-tetralones are formed as side products. Substituted 1,4-dihydroquinolines were also identified among the reaction products by Chromatographic mass spectrometry.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 800–802, June, 1981.     

New active-iron based reducing system for carbonyl compounds and imines. Stereoselective reduction of cyclic ketones

The reaction of different carbonyl compounds and imines with a mixture of iron(II) chloride tetrahydrate, an excess of lithium powder, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The new reducing system exhibited good to excellent diastereoselectivity toward the reduction of different monocyclic and polycyclic ketones.     

New method of synthesis of the 1,3,2-dioxazolidine ring

A new method of synthesis of the 1,3,2-dioxazolidine ring is developed based on the synthesis of 2-dimethylcarbamoyl-4,4-dimethyl-1,3,2-dioxazolidine by intramolecular cyclization of 1,1-dimethyl-3-(1,1-dimethyl-2-oxyethoxy)-3-chlorourea.Number 69 in the series Asymmetric nitrogen, for Number 68, see [1]; Number 43 in the series Geminal systems, for Number 42, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 393–395, March, 1989.     

Replacement of a carbonyl group of cyclic ketones by an oxygen atom: A four-step transformation of cyclic ketones into cyclic ethers

We describe a new and versatile method for transforming cyclic ketones into cyclic ethers with the same ring size in which the chirality adjacent to the carbonyl group of the ketones is retained.     

New natural compound for the enlargement of the ureter

Chemical and phytochemical investigation of the ethanol extract of the roots of Alhagi maurorum led to the isolation of a new aliphatic ester, which was named glyceryl-n-tetracosan-17-ol-1-oate on the basis of spectral data analysis and chemical reactions. This compound, in pure form, was found to enlarge the ureter.