Synthesis of difluorinated β-ketosulfones and novel gem-difluoromethylsulfone-containing heterocycles as fluorinated building blocks

A series of new heterocyclic β-ketosulfides was prepared by the reaction of the corresponding heterocyclic thiols with α-bromoacetophenone and its derivatives. Oxidation of the products using m-CPBA gave the corresponding heterocyclic β-ketosulfones, which, on treatment with Selectfluor™ under anhydrous condition underwent electrophilic fluorination resulting in new heterocycles with difluoromethylene moiety adjacent to the sulfur atom and the carbonyl group. Base-induced cleavage of the five types of the resulting products, with different heterocyclic moieties as model compounds, afforded the difluoromethyl sulfones attached to the corresponding heterocycles. They can be considered as interesting fluorinated building blocks for further elaborations.     

Heterocondensed 1,2,3‐diazaphosphorines

The reaction of phosphorus tribromide with phenylhydrazones of heterocyclic aldehydes leads to formation of a new phosphorus‐containing heterocyclic system—heterocondensed 1,2,3‐diazaphosphorines. Properties of the phosphorus‐containing heterocyclic compounds that have been synthesized are described. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:658–664, 2001     

Spectrophotometric and spectrofluorimetric studies of novel heterocyclic Schiff base dyes

Novel heterocyclic Schiff base dyes were prepared by the reaction of salicylaldehyde/2-Hydroxy-1-naphthaldehyde with different heterocyclic amines. Results of the newly synthesized compounds established by FT-IR, ¹H-NMR, ¹³C-NMR and GC–MS spectroscopic experiments were consistent with their chemical structures. Resulted heterocyclic Schiff base dyes were found to be pure from data obtained by the elemental analysis. In addition, spectrophotometric and spectrofluorimetric studies showed that these dyes were good absorbent and fluorescent. Fluorescence polarity study data revealed that some of these compounds were sensitive to the polarity of the microenvironment provided by different solvents. Time-based fluorescence steady-state measurements also showed that these heterocyclic Schiff base dyes have high photostability against photobleaching.     

Spectroscopic study of rigid-rod polymers. II. Protonation effect

The protonation of a heterocyclic rigid-rod polymer poly(p-phenylene benzbisthiazole) and its model compound has been studied by UV-visible and Raman spectroscopy. Because of the two nitrogens on the heterocyclic ring, spectroscopic features of unprotonated, half-protonated, and fully protonated structures have been identified. For the fully protonated molecule, there is also an increase in conjugation between the phenyl ring and the heterocyclic ring.     

Heterocyclic o-Chloroaldehydes as Synthons in Organic and Inorganic Sulfur Chemistry

Abstract

Many heterocyclic o-chloroaldehydes are easy to prepare, for example via the Vilsmeier chloroformylation reaction. Due to the electron withdrawing effect of the formyl group, the halogen atom is normally a nucleofuge. This can be used to prepare a range of o-substituted heterocyclic aldehydes showing interesting rearrangement reactions. Such types of compounds are also useful as starting materials for the preparation of annelated heterocyclic systems.

We have demonstrated that heterocyclic mercapto groups can be protected as t-butylthioethers. Furthermore, we have found that thiolation of heterocyclic systems containing reactive halogen substituents can conveniently be carried out via the easily prepared t-butylsulfides.

This method has been used in the preparation of a number of N₂S₂-ligands. The resulting transition metal N₂S₂-complexes have been used in the study of model systems for one of the active sites in cytochrome c oxidase. The method also gives access to polymeric heterocyclic multisulfur transition metal complexes with high electrical conductivity.     

AROMATIC AND HETEROCYCLIC DINITRILES AND THEIR POLYMERS. Ⅺ. STUDY ON THE POLYMERIZATION OF AROMATIC AND HETEROCYCLIC DINITRILES BY INFRARED SPECTROSCOPY*

The polymerization rates of fourteen aromatic and heterocyclic dinitriles were measured by infraredspectroscopy and compared with that of 4, 4′-biphenyldicarbonitrile. The rate is greatly enhancedwhen an electron withdrawing group is substituted at the para position of cyano group in aromaticdinitriles. The polymerization rates of heterocyclic dinitriles wer discussed in terms of π-lectrondensity of the heterocyclic rings.     

Heterocyclic cation radicals (review)

The modern state of the chemistry of heterocyclic cation radicals is examined, Methods for the preparation (generation) of these particles, as well as their stabilities and the factors that determine them, are described, The mechanisms of the reactions of heterocyclic cation radicals with nucleophiles and specific examples of such reactions are discussed. Special attention is directed to the role of cation radicals as intermediate particles in dehydrogenation, nitration, and radical substitution reactions and in processes involving the cleavage of C-C bonds and dehydrodimerization in the heterocyclic series. The cation radicals of some natural heterocyclic compounds and their possible role in the functioning of biochemical systems are also examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1029, August, 1980     

Efficient homo-coupling reactions of heterocyclic aromatic bromides catalyzed by Pd(OAc)2 using indium

Homo-coupling reactions of heterocyclic aromatic bromides smoothly proceeded with cat-Pd(OAc)₂, indium, and LiCl in DMF to afford exclusively symmetric biaryls possessing heterocyclic aromatic ring in good to excellent yields.     

The reaction of heteroaroyl‐substituted heterocyclic ketene aminals with 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl azide

The reaction of heteroaroyl‐substituted heterocyclic ketene aminals with 2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐glucopyranosyl azide was investigated and a series of potential bioactive compounds, 1‐glucopyranosyl‐4‐heterocyclic‐5‐heteroaryl‐1,2,3‐triazoles, were obtained in good yields. Both the reaction rate and the yield were strongly affected by the heteroaryl and heterocyclic groups. In order to improve their water solubility, the deprotection of 1‐glucopyranosyl‐4‐heterocyclic‐5‐heteroaryl‐1,2,3‐triazole was carried out. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:242–247, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10023     

Benzoylhydrazones in catalytic hydrophosphorylation

Reactions of benzoylhydrazones derived from heterocyclic and aromatic aldehydes and aliphatic, heterocyclic, and aliphatic-aromatic ketones with diethyl phosphite in the presence of [tetra(tert-butyl)phthalocyanine]aluminum chloride afford α-benzoylhydrazino phosphonates in high yields.     

Nucleophilic Reaction of Heterocyclic Enamines with Nitrile imine 1,3-Dipoles

Instead of 1,3-dipolar cycloaddition, the nucleophilic addition reaction proceeded smoothly between heterocyclic enamines 1 or 2 and nitrile imine 1,3-dipoles 3 under mild conditions to yield C-hydrazidoyl-substituted heterocyclic enamines 4--6 as the sole product.     

Cyclic Amino(Ylide) Silylene: A Stable Heterocyclic Silylene with Strongly Electron‐Donating Character

An isolable heterocyclic silylene ( 4 ) with two different π‐donating substituents, namely a classical amino group and a more electropositive and stronger carbon‐based π‐donating phosphonium ylide, was synthesized and fully characterized. The combination of these two different π‐donating substituents confers high thermal stability and an unusual nucleophilic character on silylene 4 . Therefore, silylene 4 behaves as a strong donor ligand toward transition metals with a donating character comparable to N‐heterocyclic carbenes, in contrast to classical N‐heterocyclic silylenes, which generally present a weak donating character.     

Exceptionally Strong Electron‐Donating Ability of Bora‐Ylide Substituent vis‐à‐vis Silylene and Silylium Ion

Electropositive boron‐based substituent (phosphonium bora‐ylide) with an exceptionally strong π‐ and σ‐electron donating character dramatically increases the stability of a new type of N ‐heterocyclic silylene 2 featuring amino‐ and bora‐ylide‐substituents. Moreover, the related silylium ion 4 and transition‐metal–silylene complexes, with trigonal‐planar geometries around the silicon center, are also well stabilized. Therefore, the N,B‐heterocyclic silylene 2 can be used as a strongly electron‐donating innocent ligand in coordination chemistry similarly to N ‐heterocyclic carbenes.     

Dithiadiazolyls as heterocyclic chelators: a radical approach to coordination chemistry?

The ability of heterocyclic compounds to act as chelating ligands via the cleavage of a heterocyclic E–E (or E–E′) bond with concomitant formation of M–E (and M–E′) bonds is described with particular reference to the 7π heterocyclic dithiadiazolyl radicals, R

. These electron-rich ring systems form a diversity of structural bonding types in which the heterocyclic ring can formally act as a 2e⁻, 3e⁻, 5e⁻ or 6e⁻ donor ligand. These structural bonding modes are described through examples in which the heterocyclic ring interacts with halide anions, N atoms and particularly metal centres, forming monometallic, dimetallic and trimetallic complexes. The structural features which determine which compounds are likely to act as cyclic chelators are discussed and examples of thiadiazole, diselenadiazolyl and dithiole rings acting as cyclic chelators are given.     

Synthesis of heterocyclic chromenes via Buchwald C-N coupling and the substituent effect on their photochromic properties

Synthesis of series of new heterocyclic [2]H- and [3]H-chromenes via Buchwald C-N coupling is described. Introduction of heterocyclic substituent to 6-position of benzopyrans and in 8-position of naphthopyrans led to significant bathochromic shift (up to 154 nm) in the spectra of their open forms. Substituted benzopyrans display high colorability values along with acceptable resistance to fatigue. By using judicious substituents, the absorption range of this type of pyrans can be tuned according to the nature of the heterocyclic unit, and the photochromic properties of pyrans could be adjusted to desired values.     

One-step assembly of novel carbamoyl substituted 6-oxo-4,5,6,11-tetrahydropyrrolo[1,2-b][2,5]benzodiazocine

In this work we have synthesized novel pharmaceutically relevant pyrrolo[1,2-b][2,5]benzodiazocines based entirely on the use of MCR between heterocyclic aldehyde-acid, amines, and isonitriles. The developed synthetic strategy provides an efficient one-step route to rare heterocyclic scaffold of paramount interest.     

Synthesis of functionalized pyrroles and fused pyrroles through intermolecular [3 + 2] cycloaddition reaction

A facile and efficient synthesis of pyrrole and pyrrole-fused heterocyclic compounds has been demonstrated. The current protocol involves the in situ generation of azomethine ylides which undergoes intermolecular cycloaddition reaction and subsequent treatment with DDQ provides the pyrrole and fused heterocyclic compounds in good yields.     

Domino Reactions of 3‐Vinylchromone Leading to Different Heterocyclic Compounds

A range of heterocyclic systems incorporating chromone and related scaffolds was synthesized via domino reactions of 3‐vinylchromone. These cascade processes resulted in the construction of various heterocyclic nuclei such as xanthone and enaminone as well as diazolo and triazolo chomenopyrimidine heterocycles.     

The isomerization/chlorination of nitrogen heterocyclic O,O-dialkyl thiophosphoramidates with phosphorus oxychloride—A convenient synthesis of nitrogen heterocyclic S-alkyl thiophosphoramidic acid derivatives

In this article, it is reported that the isomerization/chlorination reactions of nitrogen heterocyclic O,O-dialkyl thiophosphoramidates 5 with equivalent amounts of phosphorus oxychloride give nitrogen heterocyclic S-alkyl thiophosphorochloridates 6 and O-alkyl phosphorodichloridates 3. After removal of the by-products 3 under reduced pressure, the crude products 6 are directly reacted with various nucleophiles, NuH, in the presence of triethylamine to give nitrogen heterocyclic S-alkyl thiophosphoramidic acid derivatives 7. Thus, a new convenient method has been provided for the synthesis of the title compounds. © 1996 John Wiley & Sons, Inc.