Emmanuil I. Troyansky

Direct remote oxidation of aliphatic ketones to δ- andδ-diketones

Abstract Aliphatic ketones are converted into °- and °-diketones in one-pot oxidation reaction on treatment with Na2S2O8 in presence of Fe(II)ions.

Stereoselective Free Radical Cycloaddition-macrocyclization in Facile Synthesis of trans -cyclohexano-fused 12-membered Crown Thioethers

Homolytic cycloaddition of dithiols 1,2 derived from trans- and eis-1,2-cyclohexanediols to alkynes, induced by Pr3B-O2, offers an extremely simple approach to trans- and cis-cyclohexano-fused 12-membered crown thialactones 4a-c-7a-c. The reaction of trans-1 proceeds with pronounced remote 1,6-asymmetric induction to give predominantly (IS *, 6R *, 12S *)-4a–c, while cis-2 reacts nonstereoselectively. Basing on molecular mechanics calculations the stereoselectivity is rationalized as a result of entropy favored pathway of macrocyclization.

Regiospecific oxidative cyclization of n-methylsulfonylamines into pyrrolidines

Abstract In the framework of the approach to remote oxidative functionalization of organic compounds of various classes, which is currently under exploration by us and which is based on reactions of element-centred free radicals, the regiospecific oxidative cyclization of N-methylsulfonylalkylamines 3 into N-methylsulfonylpyrrolidines 4 has been accomplished. The more facile isomerisation of intermediate sulfonamidyl radicals 8 with 1,5-H shift in comparison with their carboxamidyl analogues 16 is, in our opinion, the chemical proof of different electronic configurations of radicals 8 (σ structure) and 16 (predominantly π structure) generated under identical conditions using Na 2S2O8CuCl2 system.

Regioselective one-step γ-chlorination of alkanesulfonamides. Preponderance of 1,5-H migration from sulfonyl versus amide moiety in sulfonylamidyl radicals

Alkanesulfomides 1 are converted regioselectively into 3-chloroalkane-sulfonamides 2 in one-pot reaction with Na2S2O8-CuCl2. N-Amylbutanesulfonamide 7 is substituted predominantly on sulfonyl moiety.

Direct oxidation of alkanoic acids and their amides to γ-lactones by peroxydisulphate-containing systems

The reaction of one-electron oxidation of alkanoic acids (I) and their amides (VI) on treatment with Na2S2O8-containing systems has been studied. As a result of the direct one-pot reaction acids (I) and amides (VI) are converted into γ- and δ-lactones, the reaction being regioselective and leading mainly to γ-lactones in up to 35% yield. The regioselectivity of the oxidative lactonisation depends greatly on the nature of alkyl substituents. The results obtained are presented in terms of a mechanism suggesting the generation of acyloxyl and amidyl radicals from (I) and (VI), respectively, followed by a rearrangement via a 1,5- or 1,6-H shift into the corresponding 3- and 4-carboxy- or -carboxamido-alkyl radicals. The latter undergo oxidative cyclisation to produce γ- and δ-lactones. The system Na2S2O8–NaCl–NaOH converts carboxamides (VI) into amines with loss of one carbon atom as a result of a Hoffmann type rearrangement.

Conformational Effects in Sulfur-Containing Six-Membered Cycles and Macrocycles

Stereochemical studies of mono- and 2,3-disubstituted 1,4-dithianes and sulfur- and oxygen-containing macrocycles by means of NMR measurements, X-ray crystal structure analysis and molecular mechanics calculations revealed new conformational regularity and peculiarities.

Conformational analysis of 2-alkyl-1,4-dithianes and related compounds by NMR spectroscopy and MMX

Abstract According to NMR (1H, 13C) spectroscopy and molecular mechanics calculations 2-alkyl substituted 1,4-dithianes exist preferentially in the conformation with equatorially oriented substituents. The conformational free energy for the methyl group in 2-methyl-1,4-dithiane is estimated to be −1.20±0.14kcal/mol. For 1,4-dithianes with substituents of the CH2X type (X = acetoxy, halogen) the predominance of axial conformers is observed originating from an intramolecular electrostatic attraction.

Regiospecific oxidative cyclization of N-methanesulfonylalkylamines: a new method of pyrrolidine ring construction

Abstract N-Methanesulfonylalkylamines cyclize regiospecifically into N-methanesulfonylpyrrolidines in one-pot oxidation reaction in Na 2S2O8-CuCl2.

Remote Asymmetric Induction in Free Radical Cycloaddition Leading to Trans-cyclohexano-fused 12-membered Crown Thioethers

Homolytic cycloaddition of dithiol 1, derived from trans-1,2-cyclohexanediol, to alkynes induced by Pr3BO2 occurs with 1,6-asymmetric induction to afford predominantly (1S∗, 6R∗, 12S∗)-trans-cyclohexano-fused 12-membered crown thialactones 4a-c. No pronounced diasteroselectivity was found in the corresponding reactions of dithiol 2, derived from cis-1,2-cyclohexanediol.

Conformational analysis of 2,3-disubstituted 1,4-dithianes by NMR spectroscopy and MMX calculations

Abstract The conformer populations for trans- and cis-2,3-disubstituted 1,4-dithianes have been determined by 1H and 13C NMR spectroscopy and calculated by molecular mechanics (MMX). The CH2X-substituents demonstrate the strong preference for axial position. The remarkable difference originating from intramolecular steric interactions has been observed between two trans-dialkyl derivatives: the trans-2,3-dimethyl-1,4-dithiane is predominantly equatorial whereas trans-2,3-dipropyl-1,4-dithiane prefers diaxial conformation. The properties of cis-2,3-dipropyl-1,4-dithiane are also unusual: its ring interconversion is unexpectedly slow (ΔG≠ = 11.2 kcal mol−1 at 26OK).