M. Shymanska

Hydrosilylation of carbonyl compounds catalysed by alkali metal fluorides in the presence of crown ethers

Abstract Hydrosilylation of the C=O bond with dimethylphenylsilane proceeds readily in low-polarity solvents (dichloromethane, benzene, THF) in the presence of the catalytic pair MF/18-crown-6 (M = Cs, Rb, K), with caesium and rubidium fluorides being the most active. Using the CsF/18-crown-6 pair, the hydrosilylation of a number of aromatic and heteroaromatic aldehydes and ketones has been carried out. Silyl ethers of the corresponding alcohols have been prepared in good yields.

Conversions of [2-(4,5-dihydrofuryl)]-silanes and -germanes under catalytic hydrogenation conditions

Abstract (2-Tetrahydrofuryl)-silanes and -germanes were obtained in high yield by the heterogeneous liquid-phase hydrogenation of [2-(4,5-dihydrofuryl)]trimethylsilane (I), bis[2-(4,5-dihydrofuryl)]dimethylsilane (II) and [2-(4,5-dihydrofuryl)]trimethylgermane with a Pd/Al 2 O 3 catalyst. The dihydrofurylsilanes I and II were found to undergo disproportionation and dehydrogenation, the latter being involved in both intra- and inter-molecular disproportionation.

Synthesis of 3-(2,5-dihydrofuryl)-silanes and -germanes and their transformations under catalytic hydrogenation conditions

Abstract A number of 3-triorganosilyl- and 3-trimethylgermyl-2,5-dihydrofurans have been prepared by the cyclization of 2-triorganosilyl(germyl)-2-butene-1,4-diols obtained from the hydrosilylation and hydrogermylation products of 1,4-bis(trimethylsiloxy)-2-butyne. It has been found that the liquid-phase heterogeneous hydrogenation of these compounds over palladium catalysts is accompanied by simultaneous isomerization and disproportionation to give the corresponding 3-(4,5-dihydrofuryl)-, 3-tetrahydrofuryl- and 3-furyl- derivatives.

Hydrosilylation of Pyridinealdehydes and Acetylpyridines Catalyzed by Caesium Fluoride in the Presence of 18-Crown-6

Abstract Reactions of isomeric pyridinealdehydes and acetylpyridines with dime thylphenylsi lane proceed readily in dichloromethane in the presence of catalytic amounts of CsF and 18-crown-6 to give silyl ethers of the corresponding pyridyl carbinols in good yields (50–70%).

The interaction of dihydrofurylsilanes with dichlorocarbene under phase-transfer conditions

Abstract Dichlorocarbene generated in a two-phase catalytic system reacts with 3-trimethylsilyl-2,5-dihydrofuran to give both possible products of mono-insertion into the CH bond in positions 2 and 5 of the ring, together with a CC bond adduct. Reaction of 2-trimethylsilyl-4,5-dihydrofuran with dichlorocarbene leads to 2,3-dichloro-2-trimethylsilyl-5,6-dihydro-2 H -pyran, which is formed via isomerization of the primary bicyclic adduct.

Influence of preparation conditions on activity and physical properties of V205-SnO2 catalyst for oxidative destruction of residual pyridine bases

Abstract At 420°C the total oxidation of pyridine bases is practically the only conversion route in the presence of V 2 O 5 -SnO 2 (molar ratio 1:0.5) catalyst prepared by calcination at 1600°C.

Alkylation of 2-Acetylpyrrole and 1 -alkyl-2-Acetylpyrroles Under Solid/Liquid Phase-Transfer Conditions

Abstract The alkylation of 2 -acetylpyrrole with alkyl iodides in the benzene/solid KOH system in the presence of 18-crown-6 at room temperature gives the corresponding 1-alkyl derivatives in high yields. The phase-transfer catalysed alkylation of 1-alkyl-2-acetylpyrroles without solvent leads to side-chain di-C-alkylated products, i.e. ketones of the (1-alkyl-2-pyrrolyl) COCHR2 type in satisfactory yields.

A Novel Synthesis of 2,6-Pyridinedicarboxylic Acid by the Ptc Auto-Oxidation of 2,6-Lutidine

Abstract 2,6-Pyridinedicarboxylic acid was obtained in 69% yield by the oxidation of 2,6-dimethylpyridine with oxygen under the action of tert-BuOK in the presence of the phase-transfer catalyst 18-crown-6.

ALKYLATION OF 3-ACETYLTHIOPHENE UNDER PHASE-TRANSFER CONDITIONS

Abstract Reactions of 3-acetylthiophene with C1-C4-alkyl iodides in a two-phase benzene/solid KOH system in the presence of l8-crown-6 afford di-C-alkylated derivatives-(3-thienyl)COCHR2 in satisfactory yields (∼50%) with high regioselectivity (70–100%).

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. The 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.