I. G. Iovel

1H, 13C and 29Si NMR study of α- and β-silylstyrenes and their adducts with dichlorocarbene

Abstract 1 H, 13 C and 29 Si NMR spectra for the α- and β-silylstyrenes ( E )-PhCHue5fbCHSiR 3 (I) and PhC(SiR 3 )ue5fbCH 2 (II) (R = Cl, Me, Ph), and those for some dichlorocarbene adducts of I and II (R = Me, Ph), were examined. From the 13 C NMR data, the phenyl substituent in the molecules I and II enhances the electronic effects of the organosilicon substituent at Cα, and weakens these effects on the C α resonance. The degree to which polarization of the vinyl Cue5fbC bond is polarized increases with increased electron-withdrawing properties of substituent R in the SiR 3 group in compounds I and II, and correlates with the reduced reactivity of the bond toward electrophilic dichlorocarbene. Several long-range coupling constants (CC) in the molecules I, II and in their adducts with :CCl 2 were measured. The estimated CC is a useful aid for the study of electronic effects in organosilicon compounds.

Hydrosilylation of heterocyclic aldehydes

The hydrosilylation of O-, S-, and N-heterocyclic aldehydes with triethylsilane has been studied in the presence of different metal complex catalysts and the corresponding silyl ethers of hetarylcarbinols obtained. The rhodium complexes Rh(PPh3)3Cl and [Et3PhCH2N]RhCl4 have been found to be the most efficient catalysts for these reactions.

1-(pyridylmethoxy)silatranes

A series of 1-(pyridylmethoxy)silatranes was obtained by the dehydrocondensation of pyridinemethanols with 1-hydrosilatrane catalyzed by potassiumtert-butylate.

Catalytic synthesis and reactions of nitrogen heterocycles (Review)

Studies at the Latvian Institute of Organic Synthesis and literature data from 1984–1994 on organic catalysis in the chemistry of N-heterocycles are reviewed. 77 to prospects for further developments in catalytic reactions of N-heterocycles are examined.

Selective catalytic oxidation of N-, O- and S-methyl-heterocyclic compounds

The vapour phase oxidation of 5- and 6-membered mono- and dimethylheterocyclic compounds in the presence of V-Mo oxide catalysts at 250–470° Beads to formation of oxygen containing products such as corresponding heterocyclic aldehydes, the anhydrides of C4–acids and cyclic ketones. This process is accompanied either by reduction or oxidation of vanadium depending on the structure of methylheterocycle. n nThe activity and selectivity of Catalysts change in parallel to changes of vanadium ions valency. It has been established that the mechanism of methylpyridine oxidation depends on the value of charge on carbon atom bound with CH3 group to be oxidized.

HYDROXYMETHYLATION OF METHYL-SUBSTITUTED PYRROLE, THIOPHENE, AND FURAN IN THE PRESENCE OF H+ CATION EXCHANGERS

In the reaction of formalin with the 2,5-dimethyl derivatives of pyrrole, thiophene, and furan in the presence of the sulfo cation exchanger Amberlyst 15 electrophilic substitution takes place at various positions of the rings with the formation of 2,5-dimethyl-1-hydroxymethylpyrrole, 1,3-dioxacycloheptano[5,6-c]-2,5-dimethylthiophene (an intermediate in the formation of which is 2,5-dimethyl-3,4-dihydroxymethylthiophene), and 2,5-hexanedione respectively. Bis(5-methyl-2-thienyl)methane was obtained from 2-methylthiophene.

Oxidation of 2,5-dimethylpyrazine with oxygen in the vapor phase on oxide catalysts and in the liquid phase in the presence of bases

The vapor-phase oxidation of 2,5-dimethylpyrazine with oxygen on vanadium-molybdenum oxide catalysts modified with silver oxide gives 5-methyl-2-formylpyrazine and 2,5-diformylpyrazine in 37% and 35% yields, respectively. Pyrazine-2,5-dicarboxylic acid was obtained in 53% yield by the liquid-phase oxidation of 2,5-dimethylpyrazine with oxygen in the presence of a strong base and an interphase catalyst.

Synthesis and catalytic oxidation of 2,5-dimethylpyrazine

The classical method for obtaining 2,5-dimethylpyrazine by cyclization of amino-acetone has been improved by use of ammonium persulfate in place of mercuric chloride in the stage of catalytic oxidation of 2,5-dimethyldihydropyrazine. Catalytic vapor phase oxidation of 2,5-dimethylpyrazine gave 5-methylpyrazine-2-aldehyde and pyrazine-2,5-dialdehyde.

IR-spectroscopic studies of the interaction of pyridine bases with vanadium and molybdenum oxides supported on magnesia

As shown by IR-spectroscopic studies, pyridine bases interacting with V2O5 and MoO3 supported on MgO form hydrogen bonds with surface hydroxyls and coordinate bonds with V and Mo ions. The interaction of 2,6-dimethylpyridine adsorbed on the surface with oxygen leads to the formation of 6-methylpyridine-2-carboxaldehyde, whose formyl group interacts with surface hydroxyls.AbstractМетодом ИК спектроскопии показано, что пиридиновые основания при взаимодействии V2O5 и MoO3, нанесенными на MgO, образуют водородные связи с поверхностными гидроксилами и координационные связи с ионами V и Mo. Взаимодействие адсорбированного 2,6-диметилпиридина с кислородом приводит к образованию на поверхности 6-метилпиридин-2-карбальдегида, формильная группа которого взаимодействует с поверхностными OH-группами.

Autooxidation of methylheterocycles under phase transfer catalysis conditions

The autooxidation of methyl- and dimethyl-substituted N-, S-, and O-heterocyclic compound derivatives has been studied in 1,2-dimethoxyethane—t-BuOK in the presence of 18-crown-6. Mono- and dicarboxylic acid derivatives of pyrazine, pyridine, pyrimidine, and thiophene have been synthesized.