S. V. Vitt

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.

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.

Unprecedented facile reactions of propane and cycloalkanes with elemental sulfur leading to dialkylsulfides and dicycloalkylsulfides

Abstract The transformations of propane and cycloalkanes into dialkyl (dicycloalkyl) sulfides under the action of elemental sulfur were achieved for the first time under very mild conditions. Sulfur is converted completely into dicylclopentylsulfide in the reaction with cyclopentane in the presence of CX 4 · n AlBr 3 (X = Cl, Br; n = 2 or 3) at −20°C for 20 min. Propane forms 1 Pr 2 S in 60% yield at 20°C after 2 h. Sulfurization of adamantane occurs in the presence of the milder electrophilic system CH 2 Br 2 AlBr 3 at 20°C to afford approximately equal amounts of Ad 2 S isomers and 1-AdSMe with the overall yield of sulfurization products of 60%.

Functionalization of saturated hydrocarbons by aprotic superacids

The inefficient formylation of adamantane by CO initiated by superacid systems based on polyhalomethanes and aluminum halides becomes selective in the presence of methylcyclopentane and affords 1-adamantanecarbaldehyde in an almost quantitative yield under mild conditions.

Functionalization of alkanes and cycloalkanes by superelectrophiles. 15. Carbonylation of cycloheptane, cyclooctane, and isomeric monoalkylcyclohexanes with CO in the presence of CBr4·2AlBr3 to form individual esters of tertiary carboxylic acids of the cyclohexane series

Cycloheptane, methylcyclohexane, cyclooctane, and ethylcyclohexane were selectively carbonylated with CO. The reactions of cycloalkanes with CO at –40 °C in the presence of the superelectrophilic system CBr4·2AlBr3 in CH2Br2 followed by treatment of the reaction mixtures with alcohols afforded esters of 1-methylcyclohexanecarboxylic acid (in the reactions of cycloheptane and methylcyclohexane) or esters of 1-ethylcyclohexanecarboxylic acid (in the reactions of cyclooctane and ethylcyclohexane) in 70—80% yields with respect to CBr4·2AlBr3. The reaction of 1,3-dimethylcyclohexane at –40 °C and the reactions of cyclooctane and ethylcyclohexane and at –20 °C proceeded nonselectively to form four isomeric esters C8H15COOR.

Carbonylation of C7C8 cycloalkanes leading to individual tertiary carbonyl-containing compounds

Carbonylation of cycloheptane, methylcyclohexane, cyclooctane and ethylcyclohexane by CO in the presence of CBr4·2AlBr3 at −40°C and 1 atm was performed with good yields and selectivities. Individual esters of tertiary carboxylic acids of the cyclohexane series were the products of these cycloalkane carbonylations.

Unusually facile transformations of cyclopentane into cyclohexanes, decalins, and adamantanes

Cyclopentane is converted into a mixture of cyclohexanes, decalins, and adamantanes (and isomeric cycloalkanes) in overall yields of 18–31% (w/w) under the action of superelectrophilic complex CBr4·2AlBr3 either in CH2X2 (X=Br, Cl) or without a solvent at 20°C.