L. N. Sobenina

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.

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.

Addition of secondary phosphines to N-vinylpyrroles

Abstract Secondary phosphines 1 – 3 react readily with N -vinylpyrroles 4 and 5 under radical initiation to give regiospecifically anti-Markovnikov adducts, diorganyl-2-(1-pyrrolyl)ethylphosphines 6a – d , highly reactive building blocks for organic synthesis, in 88–91% yields.

Direct synthesis of butadiynyl-substituted pyrroles under solvent- and transition metal-free conditions

The work describes a convenient and highly efficient C–H butadiynylation of substituted pyrroles with the use of 1-halobutadiynes. The method requires only a simple grinding of substrates in a mortar under mild, solvent- and transition metal-free conditions and constitutes the first example of pyrrole butadiynylation via cross-coupling reaction with the use of 1-halobutadiynes. The scope of this mechanochemical approach covers 4,5,6,7-tetrahydro-1H-indole, its N-substituted derivatives and 2-phenylpyrrole and on the other hand ester and phenyl end-capped 1-halobutadiynes including chlorides, bromides and iodides. Interestingly, the method has proven effective also for weak electron withdrawing aryl substituted 1-halobutadiynes what has not been yet achieved for 1-haloacetylenes. Such reactivity was unexpected in the view of the literature data and opened a gate to the plethora of substrates for organic synthesis including syntheses of pharmaceuticals. An X-ray analysis of two coupling products is also presented.

Synthesis of 2-benzoylethynylpyrroles by cross coupling of 2-arylpyrroles with 1-benzoyl-2-bromoacetylene over aluminum oxide

Cross coupling of 2-arylpyrrole with benzoylbromoacetylene over aluminum oxide at room temperature gave 45–94% of 2-(benzoylethynyl)-5-arylpyrroles. Intermediate 2-(2-benzoyl-1-bromoethenyl)-5-arylpyrroles were isolated in up to 19% yield. The reaction was accompanied by formation of less than 5% of adducts of the initial pyrroles with the cross-coupling products, 2-benzoyl-1,1-bis(5-arylpyrrol-2-yl)ethenes.

Synthesis of secondary propargyl alcohols from aromatic and heteroaromatic aldehydes and acetylene in the system KOH-H2O-DMSO

Ethynylation of aromatic and heteroaromatic aldehydes with acetylene under atmospheric pressure in the catalytic system KOH-H2O-DMSO (aldehyde-KOH molar ratio 1 : 2, −5 to −7°C, 3 h) gave secondary propargyl alcohols in 46–67% yield.

Functionally substituted 1,3-diethenyl [1,2- c ][1,3]pyrrolothiazoles from pyrrole-2-carbodithioates

The reaction of pyrrole-2-carbodithioates with methylenoactive nitriles and 2-benzoyl-1-bromoacetylene in the KOH-DMSO system leads to functionally substituted pyrrolothiazoles in 59-85% yield.

Synthesis and X-Ray Diffraction Study of 2-(2-Acyl-1-phenylethenyl)pyrroles

Pyrroles add to 2-acyl-1-phenylacetylenes on the surface of silicon dioxide at 20-90°C affording structurally stable Z-isomers of 2-(2-acyl-1-phenylethenyl)pyrroles containing a strong intramolecular hydrogen bond. The geometry of these molecules was established by X-ray diffraction analysis of a single crystal of 2-(2-benzoyl-1-phenylethenyl)-4,5,6,7-tetrahydroindole.

Strong intramolecular hydrogen bond N—H...O in 2-(2-acyl-1-phenylethenyl)-5-phenylpyrroles

The molecular structure of 2-(2-benzoyl-1-phenylethenyl)-5-phenylpyrrole and 2-(2-furoyl-1-phenylethenyl)-5-phenylpyrrole was studied by X-ray diffraction analysis at 110 K and quantum chemistry methods (B3LYP/6-31G*). In the crystalline state, both compounds have cyclic structures closed by strong intramolecular hydrogen bond N—H...O. Canonic zwitterionic structure contributes largely to the ground state of the molecules. This is probably due to synergism of the H-bonding and π-electron interactions.