A. I. Mikhaleva

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.

General Route to Symmetric and Asymmetric meso-CF3-3(5)-Aryl(hetaryl)- and 3,5-Diaryl(dihetaryl)-BODIPY Dyes

A general efficient route to hitherto inaccessible symmetric and asymmetric meso-CF(3)-BODIPY dyes has been developed. The key stages include the reduction of available 2-trifluoroacetylpyrroles to the corresponding alcohols which are further condensed with pyrroles. The method allows the BODIPY with 3(5)aryl(hetaryl) and 3,5-diaryl(hetaryl) substituents to be readily assembled. The BODIPY dyes synthesized fluoresce (Φ(f) = 0.56-1.00) in the 560-680 nm region.

1H and 13C nmr study of conformational and electronic structure of 1-vinylpyrroles

Abstract The 1H and 13C NMR spectra of some 2-alkyl- and 2,3-dialkyl-1-vinylpyrroles as well as model 1-unsubstituted pyrroles were studied. Alkyi substituents affect electronic structures of the compounds through steric inhibition of p,π-conjugation and π-induction. Correlations of the 13C chemical shifts of the pyrrole ring carbon atoms with the total charge density (CNDO/2) of these atoms are established.

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

Summary Molecules containing polarized NH fragments that behave as anion-binding motifs are widely used as receptors for recognition and sensing purposes in aprotic solvents. We present here a new example of a receptor, 3-amino-5-(4,5,6,7-tetrahydro-1H-indol-2-yl)isoxazole-4-carboxamide (receptor 1), which contains pyrrole, amide and amino subunits. This receptor shows both changes in its UV–vis absorption and fluorescence emission spectra upon the addition of F−, resulting in highly selectivity for fluoride detection over other anions, such as Cl−, Br−, I−, HSO4 −, H2PO4 − and AcO− in CH3CN. 1H NMR titration, time-dependent density functional theory (TDDFT) calculations and other experiments confirm that the sensing process is brought about by deprotonation of the pyrrole-NH in receptor 1.

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.

Pyrroles and N-Vinylpyrroles from Ketones and Acetylenes: Recent Strides

Publisher Summary This chapter describes the methods of synthesis of pyrroles and n-vinylpyrroles, their reactions, and their physicochemical and quantum chemical studies. The significant attention given to pyrroles is, mainly, due to the fact that the pyrrole nucleus is the structural unit of many fundamental compounds, important from the biological point of view, and which take part in the accumulation of solar energy, oxygen transfer processes, and other life-supporting reactions. The synthesis of pyrroles from ketones and acetylenes are considerably gaining strength as a powerful tool of pyrrole chemistry. The success of this synthesis approach, for the construction of the pyrrole nucleus, comes by complementing existing methods, for the synthesis of pyrroles, that enables easy synthesis of pyrroles, with alkyl, aryl, and hetaryl substituents, as well as various annulated pyrroles. This reaction makes available, practically, an unlimited series of N-vinylpyrroles that are readily protected NH-pyrroles, pyrrole ring-carriers, and monomers, having a wide synthetic potential.Publisher Summary This chapter describes the methods of synthesis of pyrroles and n-vinylpyrroles, their reactions, and their physicochemical and quantum chemical studies. The significant attention given to pyrroles is, mainly, due to the fact that the pyrrole nucleus is the structural unit of many fundamental compounds, important from the biological point of view, and which take part in the accumulation of solar energy, oxygen transfer processes, and other life-supporting reactions. The synthesis of pyrroles from ketones and acetylenes are considerably gaining strength as a powerful tool of pyrrole chemistry. The success of this synthesis approach, for the construction of the pyrrole nucleus, comes by complementing existing methods, for the synthesis of pyrroles, that enables easy synthesis of pyrroles, with alkyl, aryl, and hetaryl substituents, as well as various annulated pyrroles. This reaction makes available, practically, an unlimited series of N -vinylpyrroles that are readily protected NH -pyrroles, pyrrole ring-carriers, and monomers, having a wide synthetic potential.

CHAPTER 7 - Pyrroles and N-Vinylpyrroles from Ketones and Acetylenes: Recent Strides

Publisher Summary This chapter describes the methods of synthesis of pyrroles and n-vinylpyrroles, their reactions, and their physicochemical and quantum chemical studies. The significant attention given to pyrroles is, mainly, due to the fact that the pyrrole nucleus is the structural unit of many fundamental compounds, important from the biological point of view, and which take part in the accumulation of solar energy, oxygen transfer processes, and other life-supporting reactions. The synthesis of pyrroles from ketones and acetylenes are considerably gaining strength as a powerful tool of pyrrole chemistry. The success of this synthesis approach, for the construction of the pyrrole nucleus, comes by complementing existing methods, for the synthesis of pyrroles, that enables easy synthesis of pyrroles, with alkyl, aryl, and hetaryl substituents, as well as various annulated pyrroles. This reaction makes available, practically, an unlimited series of N-vinylpyrroles that are readily protected NH-pyrroles, pyrrole ring-carriers, and monomers, having a wide synthetic potential.Publisher Summary This chapter describes the methods of synthesis of pyrroles and n-vinylpyrroles, their reactions, and their physicochemical and quantum chemical studies. The significant attention given to pyrroles is, mainly, due to the fact that the pyrrole nucleus is the structural unit of many fundamental compounds, important from the biological point of view, and which take part in the accumulation of solar energy, oxygen transfer processes, and other life-supporting reactions. The synthesis of pyrroles from ketones and acetylenes are considerably gaining strength as a powerful tool of pyrrole chemistry. The success of this synthesis approach, for the construction of the pyrrole nucleus, comes by complementing existing methods, for the synthesis of pyrroles, that enables easy synthesis of pyrroles, with alkyl, aryl, and hetaryl substituents, as well as various annulated pyrroles. This reaction makes available, practically, an unlimited series of N -vinylpyrroles that are readily protected NH -pyrroles, pyrrole ring-carriers, and monomers, having a wide synthetic potential.

Study of conformations and hydrogen bonds in the configurational isomers of pyrrole‐2‐carbaldehyde oxime by 1H, 13C and 15N NMR spectroscopy combined with MP2 and DFT calculations and NBO analysis

The 1H, 13C and 15N NMR studies have shown that the E and Z isomers of pyrrole‐2‐carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole‐2‐carbaldehyde oxime is stabilized by the NH···N and NH···O intramolecular hydrogen bonds, respectively. The NH···N hydrogen bond in the E isomer causes the high‐frequency shift of the bridge proton signal by about 1 ppm and increase the 1J(N, H) coupling by ∼3 Hz. The bridge proton shows further deshielding and higher increase of the 1J(N, H) coupling constant due to the strengthening of the NH···O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by ∼3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of 1H shielding and 1J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the NH···N and NH···O hydrogen bondings to be estimated. The NBO analysis suggests that the NH···N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the NH bond through the NH···O hydrogen bond occurs in the Z isomer. Copyright

CH···N and CH···O intramolecular hydrogen bonding effects in the 1H, 13C and 15 N NMR spectra of the configurational isomers of 1‐vinylpyrrole‐2‐carbaldehyde oxime substantiated by DFT calculations

According to the 1H, 13C and 15N NMR spectroscopic data and DFT calculations, the E‐isomer of 1‐vinylpyrrole‐2‐carbaldehyde adopts preferable conformation with the anti‐orientation of the vinyl group relative to the carbaldehyde oxime group and with the syn‐arrangement of the carbaldehyde oxime group with reference to the pyrrole ring. This conformation is stabilized by the CH···N intramolecular hydrogen bond between the α‐hydrogen of the vinyl group and the oxime group nitrogen, which causes a pronounced high‐frequency shift of the α‐hydrogen signal in 1H NMR (∼0.5 ppm) and an increase in the corresponding one‐bond 13C–1H coupling constant (ca 4 Hz). In the Z‐isomer, the carbaldehyde oxime group turns to the anti‐position with respect to the pyrrole ring. The CH···O intramolecular hydrogen bond between the H‐3 hydrogen of the pyrrole ring and the oxime group oxygen is realized in this case. Due to such hydrogen bonding, the H‐3 hydrogen resonance is shifted to a higher frequency by about 1 ppm and the one‐bond 13C–1H coupling constant for this proton increases by ∼5 Hz. Copyright

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).