S. S. Spektor

Bio: S. S. Spektor is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Radical & Free-radical addition. The author has an hindex of 1, co-authored 13 publications receiving 4 citations.

Free-radical addition of alcohols toα, β-unsaturated ketones and tautomerism of formed 4-hydroxyketones

Abstract: 1. Some 4- and 5-hydroxyketones were synthesized by the free-radical addition of alcohols toα,β-unsaturated ketones. 2. According to the data of the IR spectra, the 4-hydroxyketones exist in both the open and cyclic (hemiacetal) forms. The amount of the open form increases with increase in the steric hindrance in the cyclization step. The 5-hydroxyketones exist only in the open form.

Oxidative cleavage of tertiary cycloalkanols by the lead tetraacetate-metal halide system

Abstract: The oxoalkyl radicals RCO(CH2)n+1CH2 (n=2–4) generated from five-, six-, and seven-membered 1-alkylcycloalkanols by treatment with an oxidizing system (lead tetraacetate-metal halide) are quantitatively oxidized to 1-haloalkanones.

Pb(OAc) 4 -Cu(OAc) 2 -mediated oxidation of 1-alkylcyclohexanols; β-decomposition of 1-alkylcycloalkoxy radicals

Abstract: 1. The LTA-Cu(OAc)2-mediated oxidation of tertiary cyclic alcohols produces cycloalkoxy radicals (R=alkyl; n=4–5), which undergo Β-fragmentation along two pathways: a) with ring opening to generate oxoalkyl radicals RCO(CH2)n-1CH2, which are oxidized quantitatively to Ω-unsaturated ketones, and b) with elimination of alkyl radicals (R.) and the formation of cycloalkanones. This reaction forms the basis for the synthesis of Ω-unsaturated ketones. 2. The relative rates for the two pathways of Β-decomposition depend upon the structure of the alkyl substituent. The frequency of Β-fragmentation via ring cleavage increases as the stability of the departing radical (R.) decreases: $$\dot CH_3< RCH_2 \dot CH_2< CH_3 \dot CH_2< (CH_3 )_2 \dot CH< (CH_3 )_3 \dot C< C_6 H_5 CH_2$$ . 3. The oxidation of 1-alkylcyclohexanols in which the alkyl groups exceed four carbon atoms results in the formation of alkoxy radicals which undergo oxidative cyclization and are converted into 2-alkyl-5-pentamethylenetetrahydrofurans.

Free-radical addition of alcohols to α, β- unsaturated acids under high pressure

Abstract: 1 The radical-chain process for the formation of γ-lactones from alcohols andβ-alkyl-substitutedα, β-unsaturated acids is accelerated substantially with increase in the pressure 2 Sterically hindered reactions, which practically do not go under ordinary conditions, can be run at a pressure of 10,000 kgf/cm2 to give γ-lactones in a preparative yield

Oxidative cleavage of 1-methylcycloalkanols by the Pb(IV) acetate-Cu(II) acetate system

Abstract: 1. As the result of the oxidation of C4-C7 1-methylcycloalkanols by the Pb(OAc)4-Cu(OAc)2 system, oxoalkyl radicals of type CH3CO(CH2)n+1CH2, n=1–4, are formed, which are quantitatively converted into unsaturated ketones CH3CO(CH2)nCH=CH2. 2. According to their reactivity in this reaction, 1-methylcycloalkanols can be arranged in the following series: C4>C5>C7>C6.

Biocatalytical production of (5S)-hydroxy-2-hexanone.

Abstract: Biocatalytical approaches have been investigated in order to improve accessibility of the bifunctional chiral building block (5S)-hydroxy-2-hexanone ((S)-2). As a result, a new synthetic route starting from 2,5-hexanedione (1) was developed for (S)-2, which is produced with high enantioselectivity (ee >99%). Since (S)-2 can be reduced further to furnish (2S,5S)-hexanediol ((2S,5S)-3), chemoselectivity is a major issue. Among the tested biocatalysts the whole-cell system S. cerevisiae L13 surpasses the bacterial dehydrogenase ADH-T in terms of chemoselectivity. The use of whole-cells of S. cerevisiae L13 affords (S)-2 from prochiral 1 with 85% yield, which is 21% more than the value obtained with ADH-T. This is due to the different reaction rates of monoreduction (1→2) and consecutive reduction (2→3) of the respective biocatalysts. In order to optimise the performance of the whole-cell-bioreduction 1→2 with S. cerevisiae, the system was studied in detail, revealing interactions between cell-physiology and xenobiotic substrate and by-products, respectively. This study compares the whole-cell biocatalytic route with the enzymatic route to enantiopure (S)-2 and investigates factors determining performance and outcome of the bioreductions.

Electrophotochemical Ring-Opening Bromination of tert-Cycloalkanols.

Abstract: An electrophotochemical ring-opening bromination of unstrained tert-cycloalkanols has been developed. This electrophotochemical method enables the oxidative transformation of cycloalkanols with 5- to 7-membered rings into synthetically useful ω-bromoketones without the use of chemical oxidants or transition-metal catalysts. Alkoxy radical species would be key intermediates in the present transformation, which generate through homolysis of the O-Br bond in hypobromite intermediates under visible light irradiation.

Synthesis of condensed pregnano[17,16-d]triazolines under high pressure

Abstract: Condensed pregnano[17,16-d]triazolines were produced in 1,3-dipolar cycloaddition of 16-dehydropregnenolone acetate with organic azides at 10 kbar. The structure of the synthesized compounds was determined by using two-dimensional NMR spectroscopy (1H—1H COSY, NOESY, HSQC, and HMBC).