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.     

Addition of organometallic radicals to organic substrates. Reaction between manganese decacarbonyl and α-dicarbonyl compounds

Some o-quinones and 1,2-diketones were allowed to react with manganese pentacarbonyl radicals generated in situ and the resulting persistent paramagnetic adducts studied by ESR spectroscopy. The evolution of carbon monoxide during the reaction together with the symmetrical distribution of the spin density in the organic framework (as implied by the spectral data) indicated chelation of a Mn(CO)₄ moiety by the two oxygens of the dicarbonyl substrates.One or more carbon monoxide groups can be replaced by compounds containing nitrogen, phosphorus, arsenic or antimony as binding sites. A conjugative transfer of spin density is proposed for the last three classes of substituents, while a σ mechanism is probably involved in the case of nitrogen-containing ligands.     

Electronic influences in the molecules of group IV organometallic compounds

On the basis of an analysis of the characteristic properties in the vibrational and NMR spectra of some hydrides and alkyl and vinyl derivatives of C, Si, Ge, and Sn(M), an explanation is given for an effect which appears in the organic compounds of Group IV B elements as due to an increase in the electron-acceptor properties of the heteroatoms.     

Remote stereocontrol by sulfinyl groups: reduction of delta-ketosulfoxides

The reduction of delta-ketosulfoxides constitutes the first evidence of the efficiency of the sulfinyl group to control the stereoselectivity of 1,5-asymmetric induction processes. The use of DIBAL/Yb(OTf)3 or L-Selectride as the reducing agents provides delta-hydroxysulfoxides with the opposite configuration at the hydroxylic carbon in a highly stereoselective way.     

Remote acyclic stereocontrol. Chiral synthesis of (+)-pedamide

Synthesis of optically active pedamide (3), one of the tetrahydropyran moieties of the potent insect poison pederine (1), has been accomplished through a new, remote controlled asymmetric reduction of a ketone as key step.     

Studies of adducts of main group organometallic compounds by Fourier transform Raman spectroscopy

Fourier transform (FT)-Raman spectroscopy has been used to study species that play a part in Metal Organic Vapour Phase Epitaxy (MOVPE). These compounds include N-donor adducts of (CH₃)₂Cd and (CH₃)₃Ga and the dimeric species [(CH₃)₂GaN(CH₃)₂]₂ which is a likely intermediate in the thermal production of the wide band gap semi-conductor GaN from (CH₃)₃Ga.N(CH₃)₂H. A search using FT-Raman spectroscopy for possible adducts of (CH₃)₂Cd and (C₂H₅)₂Cd with Te-donor molecules is also described. It is found that FT-Raman spectroscopy with near-infrared excitation is a particularly suitable method for studying adducts containing nitrogen heterocycles which show strong fluorescence under visible irradiation. Thus the Raman spectra of the adducts (CH₃)₂Cd.2,2′-bipyridyl and (CH₃)₂Cd.1,10-phenanthroline, which are bright yellow, have been measured.     

Addition reactions to α-cyclopropylidene ketones and aldehydes.

α-Cyclopropylidene ketones show high reactivity towards 1,4-addition reactions.     

Remote stereocontrol by sulfinyl groups: hydrocyanation of δ-ketosulfoxides

Reactions of (2-p-tolylsulfinyl)benzyl alkyl (and aryl) ketones (δ-ketosulfoxides) with Et₂AlCN in the presence of Yb(OTf)₃ take place in a completely stereoselective manner, demonstrating the efficiency of the sulfinyl group in the control of the stereoselectivity of 1,5-asymmetric hydrocyanation processes as well as the ability of Yb(OTf)₃ to form chelated species with ketosulfoxides. The behavior of their methyl derivatives at the benzylic position is dependent on the configuration at the chiral carbon. The resulting sulfinyl cyanohydrins were readily transformed into α-hydroxyamides by hydrolysis of the CN group and hydrogenolysis of the C-S bond.     

17O NMR spectroscopy in the study of group 14 organometallic compounds

A study of Group 14 organometallic compounds using ¹⁷O NMR spectroscopy carried out at the Latvian Institute of Organic Synthesis has been reviewed. The main areas of ¹⁷O NMR application—studies of electronic effects, conformational analysis and coordinative interactions—have been characterized.     

Gas chromatography of organometallic compounds of group IVB with heteroelement-heteroelement bonds

Russian Chemical Bulletin -     

Highly enantioselective michael addition of cyclic 1,3-dicarbonyl compounds to alpha,beta-unsaturated ketones

[reaction: see text] The highly enantioselective Michael addition of 1,3-cyclic dicarbonyl compounds to alpha,beta-unsaturated ketones was reported to be catalyzed by an organic primary amine derived from quinine. A chiral anticoagulant drug, (S)-warfarin, was directly prepared in 96% ee, and other related important adducts were also obtained in excellent enantioselectivity (89-99% ee).