Solid-Phase Synthesis of Nitrogen-Containing Five-Membered Heterocycles

In recent decades, a large number of reports related to solid-phase synthesis of heterocycles have appeared, owing to the wide variety of their biological activity. This review introduces the key concepts of solid-phase methodology and combinatorial synthesis with particular focus on the important role of solid-phase synthesis in the synthesis of nitrogen-containing five-membered ring heterocycles.     

Synthesis and Characterization of Novel Aromatic Polyethers from Tetraphenylated Five-Membered Heterocycle-Containing Diols and Activated Aromatic Dihalides

Abstract

New aromatic polyethers having inherent viscosities of 0.23-0.73 dL/g were synthesized from combinations of three tetraphenylated five-membered heterocycle-containing diols, 2,5-bis(4-hydroxyphenyl)-3,4-diphenyl-furan, -pyrrole, and -thiophene, and three activated aromatic dihalides, 4,4′-difluorobenzophenone, bis(4-hydroxy-phenyl) sulfone, and 2,6-difluorobenzonitrile, by aromatic nucleophilic substitution poly-condensation. These aromatic polyethers, which have an amorphous nature, were soluble in a wide range of organic solvents. They had glass transition temperatures in the 182 to 250°C range with no weight loss below 400°C in either air or nitrogen atmospheres.     

Opening of the ring of five-membered aromatic heterocycles under the influence of bases (review)

The review is devoted to a discussion of the various mechanisms of dehydration of five-membered aromatic heterocycles under the influence of bases; this reaction can be used in many cases for the synthesis of hard-to-obtain polyunsaturated acyclic compounds.Part of the material in this review was presented in a lecture given by S. Gronowitz at Moscow State University on May 31, 1976.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 435–451, April, 1978.     

Synthesis of Fused Five-Membered N,N-Heterocycles Using Microwave Irradiation

The development of new strategies for the synthesis of fused heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in the synthesis of fused five-membered heterocyclic compounds containing two nitrogen atoms is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of fused five-membered N,N-heterocycles.     

Microwave-Assisted Synthesis: Fused Five-Membered N-Heterocycles

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in nitrogen-containing fused five-membered heterocyclic compounds synthesis is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of fused N-heterocycles.     

Recent Impact of Microwave-Assisted Synthesis on Benzo Derivatives of Five-Membered N-Heterocycles

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in nitrogen-containing benzo derivatives of five-membered heterocyclic compounds synthesis is presented here, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of benzo derivatives of five-membered N-heterocycles.     

Insight into Microwave-Assisted Synthesis of Benzo Derivatives of Five-Membered N,N-Heterocycles

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in nitrogen-containing benzo derivatives of five-membered heterocyclic compounds synthesis is presented here, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of benzo derivatives of five-membered N,N-heterocycles.     

Environmentally Benign Synthesis of Five-Membered 1,3-N,N-Heterocycles by Microwave Irradiation

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in the synthesis of five-membered heterocyclic compounds containing two nitrogen atoms is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of five-membered 1,3-N,N-heterocycles.     

Advances in Microwave-Assisted Synthesis for Five-Membered N-Heterocycle Synthesis

The development of new strategies for the synthesis of small-sized heterocycles hasremained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in the synthesis of nitrogen-containing five-membered heterocyclic compounds is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of N-heterocycles.     

Highly Selective One-Pot Coupling Reaction of Indole,Aromatic Aldehydes,and 4-hydroxycoumarin Using Copper Octoate as a Homogeneous Catalyst

A facile protocol for the one-pot, multicomponent reaction of indole, 4-hydroxycoumarin, and aromatic aldehydes was developed using copper octoate as an inexpensive, commercially available, and efficient catalyst. This highly selective reaction eliminates the formation of homodimeric by-products (bisindoles and biscoumarins) and selectively results in the formation of heterodimeric adducts containing both indole and coumarin heterocycles.     

Fluoroalkylthio five-membered heteroaromatics

Fluoroalkylthio substituted five-membered ring aromatic heterocycles were prepared by direct substitution with fluoroalkylsulfenyl chlorides.     

Role of Microwaves in the Synthesis of Fused Five-Membered Heterocycles with Three N-Heteroatoms

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in three nitrogen atoms containing fused five-membered heterocyclic compounds synthesis is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of N,N,N-heterocycles. The literature data are summarized based on the type of cycles.     

Synthesis of Five-Membered N,N,N- and N,N,N,N-Heterocyclic Compounds: Applications of Microwaves

The development of new strategies for the synthesis of small-sized heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation to the synthesis of five-membered heterocyclic compounds containing three and four nitrogen atoms is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of N,N,N- and N,N,N,N-heterocycles. The literature data are summarized based on the size and type of cycles.     

肼类衍生物在五元唑类杂环合成中的应用进展

简要概述了肼类衍生物的结构及反应活性,总结了近十年来肼类衍生物分别在合成五元唑类杂环如吡唑、噻唑、1,3,4-噁二唑、1,3,4-噻二唑以及三唑类化合物,及其相关的稠杂环如吡唑并某环、s-三唑[3,4-b][1,3,4]-噻二唑、s-三唑[3,4-b][1,3,4]-噻二嗪,以及含有1,2,4-三唑的稠杂环化合物等合成中的应用进展.     

Optically active aziridine esters by nucleophilic addition of nitrogen heterocycles to a chiral 2H-azirine-2-carboxylic ester

Chiral enriched ethyl 3-methyl-2H-azirine-2-carboxylate acts as an efficient alkylating agent for a variety of five-membered aromatic nitrogen heterocycles.     

Microwave-Assisted Synthesis of Five-Membered O-Heterocycles

The development of new strategies for synthesis of five-membered O-heterocycles has remained a highly attractive but challenging proposition. An overview of the application of microwave irradiation in oxygen-containing five-membered heterocyclic compound synthesis is presented, focusing on the developments in the past 5–10 years. This contribution covers the literature concerning the total synthesis of five-membered O-heterocycles.     

Capillary Column Gas Chromatography of Environmental Polycyclic Aromatic Compounds

Abstract

The methodologies are described for isolating clean fractions of polycyclic aromatic compounds from diverse environmental samples such as air particulate matter, sediments, and fish tissue. The common step in all procedures is the separation of the polycyclic aromatic compound fraction into well-defined chemical classes by adsorption chromatography on an alumina column. These procedures greatly facilitate the detailed characterization of the polycyclic aromatic hydrocarbons, sulfur heterocycles, and nitrogen heterocycles by capillary column gas chromatography.     

An aerobic [2 + 2 + 2] cyclization via chloropalladation: from 1,6-diynes and acrylates to substituted aromatic carbocycles

A Pd-catalyzed aerobic [2 + 2 + 2] cyclization of 1,6-diynes and acrylates proceeding through a chloropalladation process has been developed. Polysubstituted five-membered aromatic carbocycles/heterocycles were obtained in good to excellent yields. The results of the mechanistic study are consistent with the proposed reaction mechanism.     

Average deviation from ideal bond order as a measure for aromaticity. AMI commuted aromatic properties of five-membered C4H4X ring systems

Average bond order deviation from that in an ideal aromatic system was proposed as a parameter for evaluation of aromaticity in general. The validity of this approach was examined by studying a series of aromatic five-membered heterocycles. The geometries and bond orders were computed with AM1 semiem-pirical method. The usefulness of AM1 semiempirical method for computation of these parameters was also discussed.     

Photochemistry of hydrogen bonded heterocycles probed by photodissociation experiments and ab initio methods

In this perspective article, we focus on the photochemistry of five-membered nitrogen containing heterocycles (pyrrole, imidazole and pyrazole) in clusters. These heterocycles represent paradigmatic structures for larger biologically active heterocyclic molecules and complexes. The dimers of the three molecules are also archetypes of different bonding patterns: N-H···π interaction, N-H···N hydrogen bond and double hydrogen bond. We briefly review available data on photochemistry of the title molecules in the gas phase, but primarily we focus on the new reaction channels opened upon the complexation with other heterocycles or solvent molecules. Based on ab initio calculations we discuss various possible reactions in the excited states of the clusters: (1) hydrogen dissociation, (2) hydrogen transfer between the heterocyclic units, (3) molecular ring distortion, and (4) coupled electron-proton transfer. The increasing photostability with complexity of the system can be inferred from experiments with photodissociation in these clusters. A unified view on photoinduced processes in five-membered N-heterocycles is provided. We show that even though different deactivation channels are energetically possible for the complexed heterocycles, in most cases the major result is a fast reconstruction of the ground state. The complexed or solvated heterocycles are thus inherently photostable although the stability can in principle be achieved via different reaction routes.