Elena Yu. Schmidt

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).

Pronounced stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the selenophenyl oximes as shown by NMR spectroscopy and GIAO calculations

In the 1H and 13C NMR spectra of 1‐(2‐selenophenyl)‐1‐alkanone oximes, the 1H, the 13C‐3 and 13C‐5 signals of the selenophene ring are shifted by 0.1–0.4, 2.5–3.0 and 5.5–6.0 ppm, respectively, to higher frequencies, whereas those of the 13C‐1, 13C‐2 and 13C‐4 carbons are shifted by 4–5, ∼11 and ∼1.7 ppm to lower frequencies on going from the E to Z isomer. The 15N chemical shift of the oximic nitrogen is larger by 13–16 ppm in the E isomer relative to the Z isomer. An extraordinarily large difference (above 90 ppm) between the 77Se resonance positions is revealed in the studied oxime isomers, the 77Se peak being shifted to higher frequencies in the Z isomer. The trends in the changes of the measured chemical shifts are well reproduced by the GIAO calculations of the 1H, 13C, 15N and 77Se shielding constants in the energy‐favorable conformation with the syn orientation of theCNOH group relative to the selenophene ring. Copyright

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

Stereochemical Study of 2-Substituted N-Vinylpyrroles

Stereochemical study of five 2-substituted N-vinylpyrroles obtained via the Trofimov reaction was carried out based on the experimental measurements of their 13C–1H and 13C–13C spin–spin coupling constants substantiated by the high-level ab initio calculations of the parent 2-methyl-N-vinylpyrrole. The title compounds were shown to adopt a predominantly skewed s-trans conformer with a noticeable population (approximately 10%) of the higher-energy skewed s-cis conformation, however, with the exception of 2-tert-butyl-N-vinylpyrrole adopting almost entirely a skewed s-trans conformation.

Base-catalyzed domino cyclization of acetylenes with ketones to functionalized cyclopentenes.

Acetylene reacts with methylaryl(hetaryl)ketones in the presence of 6.5 mol % KOH in DMSO to give diastereoselectively in single operationally functionalized cyclopentenes. This domino cyclization involving two molecules of acetylene and two molecules of ketone proceeds with the formation of four C-C bonds. The complementary assembly of the cyclopentenes with similar functionalities from acetylenes and 1,5-diketones has been developed.