Nadezhda V. Zorina

Base‐Catalyzed Stereoselective Vinylation of Ketones with Arylacetylenes: A New C(sp3)C(sp2) Bond‐Forming Reaction

Alkylaryl- and alkylheteroarylketones, including those with condensed aromatic moieties, are readily vinylated with arylacetylenes (KOH/DMSO, 100 degrees C, 1 h) to give regio- and stereoselectively the (E)-beta-gamma-ethylenic ketones ((E)-3-buten-1-ones) in 61-84% yields and with approximately 100% stereoselectivity. This vinylation represents a new C(sp(3))-C(sp(2)) bond-forming reaction of high synthetic potential.

Transition-metal-free superbase-promoted stereoselective α-vinylation of ketones with arylacetylenes: a general strategy for synthesis of β,γ-unsaturated ketones.

A wide variety of β,γ-unsaturated ketones of E configuration have been obtained in good to excellent yields via KO(t)Bu/DMSO promoted α-vinylation of aliphatic, cycloaliphatic, and alkyl aromatic (heteroaromatic) ketones with diverse arylacetylenes.

Synthesis and Optical Properties of 2-(Benzo[b]thiophene-3-yl)pyrroles and a New BODIPY Fluorophore (BODIPY = 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene)

2-(Benzo[b]thiophene-3-yl)-1-vinylpyrrole has been synthesized directly from 3-acetylbenzo[b]thiophene oxime and acetylene (flow system, KOH-DMSO, 120 degrees C, 5 h) in 68% yield. Devinylation of the synthesized pyrrole (Hg(OAc)(2), NaBH(4), 50 degrees C) led to the corresponding 2-(benzo[b]thiophene-3-yl)pyrrole in 63% yield. Trifluoroacetylation of both the pyrroles with trifluoroacetic anhydride (80 degrees C, 1 h) gave the corresponding 5-trifluoroacetyl pyrroles in 97% and 76% yields, respectively. 2-(Benzo[b]thiophene-3-yl)pyrrole was reacted subsequently with mesityl aldehyde, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and BF(3)OEt(2) to afford 4,4-difluoro-3,5-di(benzo[b]thiophene-3-yl)-8-mesityl-4-bora-3a,4a-diaza-s-indacene, a representative of the novel BODIPY fluorophore family (BODIPY = 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene), in 34% overall yield. The synthesized pyrroles exhibit promising optical properties (absorption and emission spectra, nonlinear optical (NLO) features), superior to existing analogues. The BODIPY fluorophore displays an intense red-shifted fluorescence emission in CH(2)Cl(2) (625 nm, 0.84 fluorescence quantum yield) that is fully preserved in the solid state.

A One-Pot Approach to Δ2-Isoxazolines from Ketones and Arylacetylenes

The sequential reaction of ketones with arylacetylenes and hydroxylamine in the presence of KOBu(t)/DMSO followed by the treatment of the reaction mixture with H(2)O and KOH leads to Δ(2)-isoxazolines in up to 88% yield.

A General Synthetic Strategy for the Design of New BODIPY Fluorophores Based on Pyrroles with Polycondensed Aromatic and Metallocene Substituents

BODIPYrrole: A general strategy for the design of novel BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents has been developed. The strategy involves the acylation of the condensed substituent and treatment of the acylated derivative (as oxime) with acetylene in MOH/DMSO (M = alkali metal) to give pyrroles that were then used for assembly of the BODIPY fluorophores (see scheme).

Synthesis of 2‐(Selenophen‐2‐yl)pyrroles and Their Electropolymerization to Electrochromic Nanofilms

Bridging pyrrole and selenophene chemistries: Molecular assemblies have been developed that allow scrutiny of the electronic communication between pyrrole and selenophene nuclei. Divergent syntheses of 2-(selenophen-2-yl)pyrroles and their N-vinyl derivatives from available 2-acylselenophenes and acetylenes in a one-pot procedure have been devised (see scheme), which provide access to these exotic heterocyclic ensembles.The divergent syntheses of 2-(selenophen-2-yl)pyrroles and their N-vinyl derivatives from available 2-acylselenophenes and acetylenes in a one-pot procedure make these exotic heterocyclic ensembles accessible. Now we face a potentially vast area for exploration with a great diversity of far-reaching consequences including conducting electrochromic polymers with repeating of pyrrole and selenophene units (emerging rivalry for polypyrroles and polyselenophenes), the synthesis of functionalized pyrrole-selenophene assembles for advanced materials, biochemistry and medicine, exciting models for theory of polymer conductivity.

Comparative analysis of hydrogen bonding with participation of the nitrogen, oxygen and sulfur atoms in the 2(2′-heteroaryl)pyrroles and their trifluoroacetyl derivatives based on the 1H, 13C, 15N spectroscopy and DFT calculations

The NHċbondX (X = N,O,S) intramolecular hydrogen bond in the series of 2(2′‐heteroaryl)pyrroles and their trifluoroacetyl derivatives is examined by the 1H, 13C, 15N spectroscopy and density functional theory (DFT) calculations. The influence of the hydrogen bond on coupling and shielding constants is considered. It is shown that the NHċbondN intramolecular hydrogen bond causes a larger increase in the absolute size of the 1J(N,H) coupling constant and a larger deshielding of the bridge proton than the NHċbondO hydrogen bond. The effect of the NHċbondS interaction on the 1J(N,H) coupling constant and the shielding of the bridge proton is small. The NMR parameter changes in the series of the 2(2′‐heteroaryl)pyrroles due to NHċbondX hydrogen bond and the series of the 1‐vinyl‐2‐(2′‐heteroaryl)‐pyrroles due to CHċbondX hydrogen bond have the same order. The proximity of the nitrogen, oxygen or sulfur lone pair to the FċbondH hydrogen bridge quenches the trans‐hydrogen bond spin–spin couplings 1hJ(F,H‐1) and 2hJ(F,N). Copyright

1,2-Dioximes in the trofimov reaction

Abstract3,3′-Dimethyl-1,1′-divinyl-2,2′-dipyrrole was obtained during the reaction of 3,4-hexanedione dioximes with acetylene under pressure in the potassium hydroxide-DMSO system. In the case of 1,2-cyclohexanedione dioxime 2,2′-dipyrrole and 2-pyridyl-and 2-acylpyrroles were isolated. α-Benzil and α-furil dioximes give 3,4-diphenyl-and 3,4-di(2-furyl)-1,2,5-oxadiazoles respectively in addition to their mono-and divinyl derivatives.

Fluorescence quenching and laser photolysis of dipyrrolylbenzenes in the presence of chloromethanes

Fluorescence quenching of 1,4-bis(1H-pyrrol-1-yl)benzene, 1-(1H-pyrrol-2-yl)-1-(1-vinyl-1H-pyrrol-1-yl)benzene, and 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene with chloromethanes (methylene chloride, chloroform, and carbon tetrachloride) in solvents with different polarities follows electron-transfer mechanism. The occurrence of an electron-transfer step is confirmed by formation of short-lived pyrrolylbenzene radical cations. An exception is quenching of fluorescence of 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene in n-hexane in the presence of CCl4 and CHCl3 and in pure CCl4. In this case, neutral 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene·-Cl radical is formed via recombination of 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene radical cation and chloride anion. A relation was found between the nature of the short-lived species detected by laser photolysis and stable product obtained by stationary photolysis.

One-pot synthesis of 1-ethynylcyclohexyl vinyl ether from cyclohexanone and acetylene

Vinyl ether derived from tertiary acetylenic alcohols have not been reported so far. The reason is that such alcohols are unstable on heating in the presence of bases (classical retro-Favorskii reaction) [1–3]. Nevertheless, insofar as the Favorskii reaction is reversible, we can presume that O-vinylation of a tertiary acetylenic alcohol present in the reaction mixture even at a small concentration should eventually lead to expected vinyl ether due to continuous displacement of the equilibrium (Scheme 1). Therefore, vinyl ethers of tertiary acetylenic alcohols could be obtained in one step by heating ketones with acetylene in the presence of a base. Screening of the reaction conditions and superbasic catalytic systems, as well as of ketones and acetylenic compounds used as reactants, has shown that 1-ethynylcyclohexyl vinyl ether (III) is indeed formed upon treatment of cyclohexanone (I) with acetylene in the presence of a base. In the reaction performed in a suspension of KOH in DMSO (molar ratio I–KOH 1 : 1) at 90°C under acetylene pressure the yield of vinyl ether III reached 40% (Scheme 2). An important condition is acetylene pressure which ensures its high concentration in the liquid phase and favors displacement of equilibrium toward formation of 1-ethynylcyclohexan-1-ol (II) which then undergoes vinylation (Scheme 2). ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 6, pp. 858–859.