A. M. Genaev

New chiral ligands based on (+)-α-pinene

A number of new chiral ligands were synthesized starting from an accessible monoterpene, (+)-α-pinene. The new ligands were used in the vanadium-catalyzed oxidation of sulfides to chiral sufoxides.

Degenerate rearrangement of detectable 9,10-dimethyl-9-vinyl-phenanthrenium ion : 1,2-shift of the vinyl group

Dynamic NMR study showed that 9,10-dimethyl-9-vinylphenanthrenium ion, generated under the conditions ensuring its “long life,” undergoes very fast (ΔG≠ = 24.4 kJ/mol at −103°C) degenerate 1,2-shift of the vinyl group. According to the DFT quantum-chemical calculations, the process is one-step, and the low energy of formation of the activated complex is determined by effective participation of π electrons of the vinyl group in delocalization of the positive charge; no such delocalization is intrinsic to the initial ion.

Carbocationic Cyclizations: IX. Rearrangement of Long-Lived 4-(2-Biphenylyl)-1,2,3,4-tetramethylcyclobutenyl Cation into trans- and cis-4,5,6,6-Tetramethyl-4,5,6-trihydrocyclopenta[j,k]phenanthren-5-yl Cations

According to the 1H and 13C NMR data, long-lived 4-(2-biphenylyl)-1,2,3,4-tetramethylcyclobutenyl cation generated by protonation of 3-(2-biphenylyl)-1,2,3-trimethyl-4-methylenecyclobutene in super-acids undergoes cyclization which launches further rearrangements finally leading to formation of a mixture of trans- and cis-4,5,6,6-tetramethyl-4,5,6-trihydrocyclopenta[j,k]phenanthren-5-yl cations.

Degenerate rearrangement of long-lived 9-cyclopropyl-9,10-dimethyl-9,10-dihydrophenanthren-9-ylium: Migration of cyclopropyl group

Dynamic NMR study showed that long-lived 9-cyclopropyl-9,10-dimethyl-9,10-dihydrophenanthren-9-yl cation generated from 9-cyclopropyl-9,10-dimethyl-9,10-dihydrophenanthren-9-ol in HSO3F-SO2ClF-CD2Cl2 at −100 to −75°C undergoes fast degenerate 1,2-shift of the cyclopropyl group. The Arrhenius parameters for this process were determined: Ea = 33.7 kJ/mol, log A = 13.0.

Energy barriers to carousel rearrangements of carbocations: Quantum-chemical calculations vs. experiment

By DFT method energy barriers were calculated for carousel rearrangements of bicyclo[3.1.0]hexenyl, cyclobutenyl, and homotropylium cations. A plausible agreement between calculated and experimental findings was found.

Reaction of 10,10-dimethyl-9-trimethylsiloxy-9,10-dihydrophenanthrene-9-carbonitrile with acids

The behavior of 10,10-dimethyl-9-trimethylsiloxy-9,10-dihydrophenanthrene-9-carbonitrile in trifluoromethanesulfonic acid and acid systems CF3SO3H-CD2Cl2, HSO3F-SO2ClF-CD2Cl3, and CF3COOH-CD2Cl2 were studied by NMR spectroscopy. Principal reaction schemes were determined; the first step in these schemes is protonation of the initial compound at the oxygen or nitrogen atom.

Long-Lived 9-Cyano-9,10-dimethylphenanthrenyl Cation. Migration of Cyano Group in Carbocations

Long-lived 9-cyano-9,10-dimethylphenanthrenyl cation was generated in superacidic medium, and its structure was determined by 1H and 13C NMR spectroscopy. The energy barrier to 1,2-shift of the cyano group in 9-cyano-9,10-dimethylphenanthrenyl cation was estimated by NMR and DFT calculations.

Hydrogenation and conformational analysis of (1R,2R,6S)-3-methyl-6-(1-methylethenyl)cyclohex-3-ene-1,2-diol

Hydrogenation of (1R,2R,6S)-3-methyl-6-(1-methylethenyl)cyclohex-3-ene-1,2-diol was studied. Nickel chloride-sodium tetrahydridoborate system turned out to selectively reduce the double bond in the isopropenyl group. The results of conformational analysis of (1R,2R,6S)-3-methyl-6-(1-methylethenyl)cyclohex-3-ene-1,2-diol and its partly and completely hydrogenated derivatives were in a good agreement with the NMR data.

Degenerate rearrangement of 9-isopropenyl-9,10-dimethyl-phenanthren-9-yl and 9,10-dimethyl-9-(trans-1-methylprop-1-en-1-yl)phenanthren-9-yl cations

Abstract1H NMR study has shown that long-lived 9-R-9,10-dimethylphenanthren-9-yl cations (R = isopropenyl, trans-1-methylprop-1-en-1-yl) generated in the system HSO3F-SO2ClF-CD2Cl2 at −130°C undergo degenerate rearrangement via 1,2-vinyl shifts (ΔG’ = 37 and 39 kJ/mol, respectively, at −88°C). Analysis of the geometric parameters of the initial structures and transition states calculated by the DFT method indicates that unfavorable steric factors are responsible for the sharp deceleration of 1,2-shifts of the isopropenyl and trans-1-methylprop-1-en-1-yl groups as compared to vinyl and cis-1-methylprop-1-en-1-yl groups, respectively.

Structure of long-lived alkynyl-substituted carbocations of the phenanthrene series and their precursors

According to the NMR data, 9-(R-ethynyl)-9-hydroxy-10,10-dimethyl-9,10-dihydrophenanthrenes (R = H, Me, Ph) in superacid medium (HSO3F-SO2ClF) at low temperature undergo dehydroxylation with formation of the corresponding long-lived 10,10-dimethyl-9-(R-ethynyl)-9,10-dihydrophenanthren-9-yl cations which do not isomerize to 10-(R-ethynyl)-9,10-dimethyl-9,10-dihydrophenanthren-9-ylium. In contrast, longlived 10,10-dimethyl-9-(3,3,3-trifluoroprop-1-yn-1-yl)-9,10-dihydrophenanthren-9-yl cation derived from 9-(3,3,3-trifluoroprop-1-yn-1-yl)-10,10-dimethyl-9,10-dihydrophenanthren-9-ol undergoes partial isomerization to 10-(3,3,3-trifluoroprop-1-yn-1-yl)-9,10-dimethyl-9,10-dihydrophenanthren-9-yl cation.