Kseniya N. Sedenkova

Three-Component Heterocyclization of gem-Bromofluorocyclopropanes with NOBF4: Access to 4-Fluoropyrimidine N-Oxides

Novel three-component heterocyclization involving gem-bromofluorocyclopropanes, nitrosyl tetrafluoroborate, and a molecule of the solvent (nitrile) yielding previously unknown fluorinated pyrimidine N-oxides is described. A two-step synthetic approach to 4-fluoropyrimidine N-oxides from alkenes under mild conditions is developed using this reaction. Mechanistic aspects of the heterocyclization are discussed.

Synthesis of amino acids of cyclopropylglycine series

The review covers methods of synthesis of amino acids of the cyclopropylglycine series published in the past decade. Main methods of synthesis of cyclopropylglycines are based on the carbene and ylide addition to alkenes, enzymatic reactions, the Kulinkovich cyclopropanation of esters and amides, MIRC reactions, the modification of cyclopropanecarbaldehydes by the Strecker reaction, and other transformations of functional groups of cyclopropanes. Particular attention is given to 2-carboxycyclopropylglycines and 3,4-methanoprolines. These compounds have attracted interest as conformationally rigid cyclopropane-containing analogs of glutamic acid and proline and also as components of physiologically active peptides. The physiological properties of cyclopropylglycines are briefly characterized.

Carbenoid rearrangement in the series of substituted gem-dibromospiropentanes

A series of new substituted gem-dibromospiropentanes was studied in a reaction with methyllithium at −55...−50°C. This reaction is a carbenoid rearrangement that leads to the formation of monomeric and dimeric bromocyclobutenes and also to the products of cyclobutylidene insertion into a C-H bond of the solvent depending on the character of substituents in the dibromospiropentane fragment.

symm-Tetramethylenecyclooctane: En Route to Polyspirocycles

A straightforward gram-scale synthesis of 1,3,5,7-tetrakis(methylidene)cyclooctane (TMCO) from commercial adamantane-1,3-dicarboxylic acid has been developed. TMCO exhibits high reactivity toward a number of carbenes and epoxidizing reagents, undergoing multiple cyclopropanations, dihalocyclopropanations, or epoxidations of four double bonds to yield polyspirocyclic products. Stereochemical features of polyspirocyclopropanated compounds have been thoroughly examined in experimental (NMR) and theoretical (DFT) studies. Comprehensive stereochemical assignment of TMCO adducts with dihalocarbenes and spiroepoxy products was achieved. The conditions of the formation of 1-methyl-3,7-bis(methylidene)bicyclo[3.3.1]nonane from the adamantane derivative were optimized, and diadducts of this diene with dihalocarbenes were isolated and characterized.

Beyond the Dimer and Trimer: Tetraspiro[2.1.25.1.29.1.213.13] hexadecane‐1,3,5,7‐tetraone—the Cyclic Tetramer of Carbonylcyclopropane

Tetraspiro[2.1.2(5).1.2(9).1.2(13).1(3)]hexadecane-1,3,5,7-tetraone 4, a unique tetraketone containing a cyclooctane core and four spiroannelated cyclopropane moieties, represents the previously unknown cyclotetramer of carbonylcyclopropane. For this purpose oxidation of the parent polyspirocyclic hydrocarbon was examined under various oxidative conditions, and the reactivity of oxidants towards methylene groups of the eight-membered cycle, activated by adjacent spirocyclopropane rings, was evaluated and contrasted. Whereas the treatment of tetraspirohexadecane with ozone resulted in monooxidation, its reaction with methyl(trifluoromethyl)dioxirane afforded the product of four-fold oxidation, triketoalcohol 10. Subsequent oxidation of the latter with Dess-Martin periodinane gave the target tetraketone 4.

Synthesis of alkoxy- and phenylsulfanyl-substituted 1,1-dihalospiro[2.2]pentanes and their reactivity toward methyllithium

A number of new alkoxy- and phenylsulfanyl-substituted 1,1-dihalospiro[2.2]pentanes bearing different halogen atoms were synthesized. 1,1-Dihalo-4-tert-butoxyspiro[2.2]pentanes reacted with methyllithium at −55 to −10°C to give exclusively 1-tert-butoxy-2-vinylidenecyclopropane. The reaction of 1-bromo-1-fluoro-4-phenylsulfanylspiro[2,2]pentane with methyllithium resulted in replacement of the fluorine atom by methyl group.