Dmitry V. Demchuk

Rearrangements of organic peroxides and related processes

Summary This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O–O-bond cleavage. Detailed information about the Baeyer−Villiger, Criegee, Hock, Kornblum−DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately.

Electrochemically induced multicomponent assembling of isatins, 4-hydroxyquinolin-2(1H)-one and malononitrile: a convenient and efficient way to functionalized spirocyclic [indole-3,4′-pyrano[3,2-c]quinoline] scaffold

Electrochemically induced catalytic multicomponent transformation of isatins, 4-hydroxyquinolin-2(1H)-one and malononitrile in ethanol in an undivided cell in the presence of sodium bromide as an electrolyte results in the formation of spirooxindoles with fused functionalized indole-3,4′-pyrano[3,2-c]quinoline] scaffold in 75–91% substance yields and 500-600% current yield. The developed efficient electrocatalytic approach to medicinally relevant [indole-3,4′-pyrano[3,2-c]quinoline] scaffold is beneficial from the viewpoint of diversity-oriented large-scale processes and represents a novel example of facile environmentally benign synthetic concept for electrocatalytic multicomponent reactions.

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.

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.

Copper(I)-mediated synthesis of β-hydroxysulfones from styrenes and sulfonylhydrazides: an electrochemical mechanistic study

Copper(I) halides were used as mediators in the synthesis of β-hydroxysulfones via the oxysulfonylation of styrenes using sulfonylhydrazides. The feature of the developed process lies in the combination of a copper(I) salt with oxygen—the stoichiometric oxidant. Copper(II) species are responsible for the oxidation of sulfonylhydrazides, they are generated in small amounts in the O2/Cu(I)/Cu(II) redox system, which is formed during the reaction. The combination of these three components enables one to obtain in the case of α-methylstyrenes only β-hydroxysulfones and in the case of α-unsubstituted styrenes, β-hydroxysulfones as the main products and β-ketosulfones as the by-products. With good yields β-hydroxysulfones were prepared by reduction of the reaction mixture containing both products β-hydroxysulfones and β-ketosulfones with NaBH4. An electrochemical study revealed that the Cu(I)/Cu(II) pair can serve as an effective mediator of β-hydroxysulfones formation via redox processes.

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).

SOME NEW HOMOLYTIC HETEROCYCLIZATION REACTIONS IN CHEMISTRY OF BIVALENT SULFUR COMPOUNDS

Abstract The novel approach to one-pot synthesis of various heterocycles based on the heterocyclization reaction of bivalent sulfur compounds (thiols, dithiocarboxylic acids and their derivatives) are reported.

Homolytic reactions of dithiols with alkynes: A method of synthesis of 1,3- and 1,4-dithiacycloalkanes

The homolytic addition of alkanedithiols to alkynes gives 5–7-membered 1,3- or 1,4-dithiacycloalkanes, depending on the structures of the components

Homolytic cyclization of 1,3-propanedithiol to 1,2-dithiolane in the presence of 2,5-dimethyl-2,4-hexadiene

Abstract2,2-Diethyl-1,3-propanedithiol undergoes cyclization to 4,4-diethyl-1,2-dithiolane upon interaction with 2,5-dimethyl-2,4-hexadiene in benzene in the presence of azodiisolbutyronitrile. The reaction proceeds according to the radical chain mechanism.