I. S. Akhrem

The cleavage of SiC bonds by transition metal compounds. Methylation and phenylation of olefins by organosilicon compounds in the presence of palladium salts

Abstract Palladium(II)compounds are able to cleave SiR bonds in various alkyl- and aryl-silanes, and linear and cyclic siloxanes and silazanes at 60–120°. The Group VIII metals and metal compounds PdCl2, H2PtCl6, H2PtCl6 + SnCl2, Pt(PPh3)3, Pt(PPh3)4, Pt/C and Pd catalyse the cleavage of the SiMe bond in hexamethyldisiloxane at 100–200° to give linear trisiloxane as the main product. This reaction which involves the transfer of methyl or phenyl groups from the Si to the Pd atom, can be used for methylation and phenylation of olefins by organosilicon compounds.

Ionic bromination of ethane and other alkanes (cycloalkanes) with bromine catalyzed by the polyhalomethane·2AlBr3 aprotic organic superacids under mild conditions

Abstract The polyhalomethane·2AlBr 3 aprotic organic superacids were shown to effectively catalyze low-temperature ionic bromination of (cyclo)alkanes. Ethane readily reacts with Br 2 at 55–65 °, affording mainly 1,2-dibromoethane. Propane, butane, and C 5 -C 6 cycloalkanes react at [fd9365-1], resulting in monobromides with high yields and good selectivity.

Transformatioms of cycloalkanes under the action of acyl halides in the presence of AIBr3.

Abstract Cycloalkanes have been found to react with acyl halides in the presence of AIBr3, (mole ratio RCOX:AIBr3 = 1:2) under very mild conditions affording products of hydrocarbon oxidative coupling or/and hydrocarbon acylation.

The first examples of selective carbonylation of n-butane and n-pentane

Abstract The polyhalomethane based superelectrophilic systems allowed us to accomplish the first efficient and selective carbonylation of n-butane and n-pentane with CO. Depending on the nature of the superelectrophilic system, Me 3 CCOOR or EtCH(Me)COOR (R = H, Alk) can be obtained at −20°C, 1 atm from n-butane and CO after water (or alcohol) treatment in ≈ 90% yield based on the superelectrophilic system. Pentane reacts with CO in the presence of the CBr 4 ·2AlBr 3 superacid to give a single product, EtC(Me) 2 COOR, in almost quantitative yield.

An effective formylation of adamantane with CO initiated by the aprotic organic superacid CBr4·2AlBr3 under mild conditions

Abstract The reaction of adamantane with carbon monoxide at −45° ÷ +20° C over 0.5–2 h, catalyzed by the aprotic organic superacid CBr 4 ·2AlBr 3 , is described. The formylation of adamantane under CO atmosphere at 0 ÷ +20°C in the presence of methylcyclopentane as a source of hydride ion affords 1-adamantanecarbaldehyde (1) in yield 70–72% on adamantane for 1 h.

Functionalization of saturated hydrocarbons

Alkanes and cycloalkanes (isobutane, butane, isopentane, isohexane, and methylcyclopentane) react with benzene or bromobenzene at 0–20 °C in the presence of RCO+Al2X7− complexes (R=Me, Pr, or Ph; X=Cl or Br) to give products of the alkylacylation of arenes. The yields of alkylated aromatic ketones reach 60–87 % in 5–30 min, whereas the yields of unalkylated aromatic ketones (the competitive reaction) reach 0–40 %. The reactions of isobutane or isopentane with benzene result exclusively inpara isomers oft-BuC6H4COR or a mixture of Me2(Et)CC6H4COR and Me(i-Pr)CHC6H4COR isomers (1∶1), respectively. The reaction of isobutane with benzene also proceeds regioselectively and gives only one isomer, 2-Br-t-BuC6H4COR.

A new efficient and selective synthesis of ketones from alkanes or cycloalkanes, CO, and silanes in the presences of aprotic superacids

A new approach to the direct synthesis of ketones from alkanes or cycloalkanes (RH), CO, and silanes is proposed. Ketones were obtained in 50–97% yields from propane, butane, cyclopentane, cyclohexane, and methylcyclopentane on treatment with CO and silanes (Me4Si, Et4Si, orm- andp-XC6H4SiMe3, where X=Cl, Me, OMe) in the presence of CX4·2AlBr3 (X=Br, Cl) superacids at 0°C. The reactions withm- andp-XC6H4SiMe3 (X=Cl, Me) occur regioselectively to givem-ketones fromm-silanes andp-ketones fromp-silanes. However, the only product,p-MeOC6H4COR, is formed both fromm- andp-MeOC6H4SiMe3. The reaction ofcyclo-C5H9CO+ with BzSiMe3 results in an organosilicon ketone, Me3SiCH2C6H4COC5H9, while in the presence of an excess of an acylating system (after alcoholysis), Me2Si(OR′)CH2C6H4COR is formed.

Unprecedented alkylation of pentafluorobenzene with propane

Propane has been found to alkylate pentafluorobenzene in the presence of aprotic organic superacids CBr4·nAlBr3 (n = 1 or 2) in CH2Br2 solution at 0°, giving C6F5Pri (1) in almost quantitative yield. In the absence of propane at the 20°, pentafluorobenzene reacts with CBr4·2AlBr3 to form C6F5CBr3 in 40 % yield.

First examples of superelectrophile initiated iodination of alkanes and cycloalkanes

Direct iodination of alkanes and cycloalkanes in the presence of superelectrophiles has been accomplished for the first time. The reactions of saturated hydrocarbons with I2 in the presence of CCl4·2AlI3 at −20°C afforded monoiodides in good yields and selectivities.

Functionalization of saturated hydrocarbons by aprotic superacids 5. Regioselective carbonylation of propane in an organic solvent initiated by aprotic organic superacids CX4·nAlBr3 (X = Br, Cl;n = 1 or 2)

Aprotic organic superacids CX4 ·nAlBr3 (X = Br, CI; n = 1 or 2) are effective initiators of carbonylation of propane with CO in an organic solvent at -10 to -20 °C.