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.     

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond

N-Alkoxymethylation of heterocyclic compounds with diethyl phosphite via cleavage of P-O bond was investigated and a series of N3-ethoxymethylated heterocyclic compounds were synthesized. A mechanism in which diethyl phosphite acts as an efficient surrogate of ethanol was proposed and supported by several evidences.     

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.     

Novel synthesis of medium-sized oxa-heterocycles by palladium-catalyzed intramolecular Heck reaction

An efficient and high yielding method for the synthesis of eight-membered heterocyclic skeletons has been developed via palladium-catalyzed intramolecular Heck reaction.     

Synthesis of ethyl 4,5-disubstituted 2-azido-3-thiophenecarboxylates and use in the synthesis of thieno[3,2-e][1,2,3]triazolo[1,5-a]pyrimidin-5(4H)-ones

New heterocyclic azides, ethyl 2-azido-4-R¹-5-R²-3-thiophenecarboxylates, were synthesized by diazotization of 2-aminothiophenes and subsequent treatment with sodium azide. The reactions of these heterocyclic azides with β-ketoesters and activated acetonitriles were studied. The derivatives of thieno[3,2-e][1,2,3]triazolo[1,5-a]pyrimidine, a new ring system, were prepared in high yields via an anionic hetero-domino reaction.     

Synthesis of N-heterocyclic ligands for use in affinity and mixed mode chromatography

A set of heterocyclic ligands have been synthesised for use in the preparation of mixed mode affinity chromatographic adsorbents for application in the purification of proteins, including antibodies. The ligand structures were designed to consist of a pyridinyl or related aza-heterocyclic nucleus bearing a pendant arm containing either an alkylamine, alkylthiol or hydroxyalkyl nucleophilic group to allow their facile immobilisation onto an activated support matrix. Ligand diversity was achieved by altering the length of the alkyl chain between the heterocyclic nucleus and nucleophilic group, varying the position of alkyl chain attachment to the heterocycle, and incorporating extra substituents into the pyridinyl or related aza-heterocyclic ring. This diversity in ligand structure was intended to enable key structural features of the ligand, required for efficient protein binding, to be determined. In contrast to the previously used multi-step procedures for the preparation of analogous substituted pyridine or aza-heterocyclic compounds, the synthesis routes for the ligands described here have generally utilized very mild, one-step reactions with readily available heterocyclic precursors.     

An efficient synthesis of novel heterocycle-fused derivatives of 1-oxo-1,2,3,4-tetrahydropyrazine using Ugi condensation

We present a convenient synthesis of novel pyrrole- and indole-fused 1-oxo-1,2,3,4-tetrahydropyrazine heterocyclic structures using a novel modification of four-component Ugi condensation. We demonstrate the usefulness and versatility of the developed approach for the synthesis of variously substituted compounds, and discuss the scope and limitations of the chemistry involved.     

Novel triazolopeptides: chirospecific synthesis and conformational studies of proline derived analogs

Replacing the backbone amide function by a heterocyclic bioisostere, [3+2] azide-alkyne cycloaddition has been applied for the construction of biologically relevant peptidomimetics. Starting from aminoalkynoates, triazole formation was accomplished by addition of hydrazoic acid. NMR studies displayed that the newly developed 4,5-triazolopeptides, which incorporate a biomimetic triazole NH-function as polar constraint element, showed a substantially higher tendency to form a cis-prolyl-geometry than a comparable native peptide sequence.     

Synthesis and characterization of benzo[c]thiophene analogs tethered with dibenzo-heterocycles as potential OLEDs

Synthesis of mixed heterocyclic system containing benzo[c]thiophene, dibenzo-heterocycles, and thiophene unit is described.     

Polyisobutylene-supported N-heterocyclic carbene palladium catalysts

This paper describes how the nonpolar polymer polyisobutylene (PIB) can be used as a handle to prepare PIB-bound NHC ligands that are soluble in monophasic mixtures of mixed solvents but phase separable when such solvent systems are perturbed to be biphasic. The results here show that such PIB-bound NHC ligands can be used to synthesize useful palladium catalysts. In this paper, both PIB-bound analogs of an N,N′-bis(2,6-diisopropylphenyl) heterocyclic carbene and simpler N,N′-dialkyl heterocyclic carbene ligand were prepared and were successfully used to form palladium cross-coupling catalysts. The reactivity, recycling and reusability of these catalysts has been examined.     

New 5-(2-ethenylsubstituted)-3(2H)-furanones with in vitro antiproliferative activity

A convenient route to new 3(2H)-furanones is described through hydrogenolysis and subsequent acidic hydrolysis of isoxazoles. The antiproliferative activity of title compounds were evaluated against leukemia-, carcinoma-, neuroblastoma-, and sarcoma-derived human cell lines in comparison to the natural compound geiparvarin. The structure activity relationship indicated that the maximum in vitro antiproliferative activity correlates with the presence of a heterocyclic ring on the ethenyl moiety.     

Efficient and selective deprotection method for N-protected 2(3H)-benzoxazolones and 2(3H)-benzothiazolones

Cyclic carbamate flanked with heterocyclic or aliphatic moieties are frequently used in medicinal chemistry. The synthesis of derivatives bearing a free NH often requires the use of a protection method. A literature search reveals very few protection/deprotection methods for cyclic carbamates. In this paper, we described different methods applicable to 2(3H)-benzoxazolone and 2(3H)-benzothiazolone.     

Synthesis of 3,4-dihydrobenzo[g]isoquinoline-1(2H)-ones and 3,4-dihydroisoquinoline-1(2H)-ones skeleton via intramolecular electrophilic cyclization

An original alternative approach to isoquinolines based on the installation of a benzene nucleus on a performed heterocyclic ring. Synthesis of 3,4-dihydrobenzo[g]isoquinoline-1(2H)-ones and 3,4-dihydroisoquinoline-1(2H)-ones via intramolecular electrophilic cyclization of 3,4-disubstituted lactams is reported.     

1,1-Dihydropolyfluoroalkylsulfides—versatile synthons in fluoroorganic chemistry

The synthetic potential of 1,1-dihydropolyfluoroalkylsulfides, which can be easily prepared from 1,1-dihydropolyfluoroalkanoles, is studied. New methods of the synthesis of fluorine-containing acyclic, carbocyclic and heterocyclic compounds are described.     

A novel and facile synthesis of 7,8-diacylcoumarins

Oxidation of N-carbonylhydrazones of 7-hydroxy-8-acetylcoumarin with lead tetraacetate results in the synthesis of 7,8-diacylcoumarins in good yields. The reaction proceeds via the transformation of a hydroxy into an acyl group reported for the first time in heterocyclic chemistry.     

Reactions of 2-bromopropanamides with conjugated bases of representative β-dicarbonyl compounds. Synthesis of 2,5-dioxopyrrolidines and oxazolidine-4-ones

Reactions of 2-bromopropanamides with potassium enolates of representative β-dicarbonyl compounds provide, in high yields, open and heterocyclic compounds through a CC or CO alkylation reaction. Whereas C-alkylation products form in all conditions tested under relevant diastereoselectivity, O-alkylation takes place only in the presence of silver promoters, and shows partial diastereoselectivity.     

Rapid access to benzo-annelated heterocycles, naphthalenes, and polysubstituted benzenes through a novel benzannulation reaction

A novel, efficient, and powerful methyl mercaptoacetate triggered benzannulation reaction is described. The precursors are heterocyclic, aromatic or acyclic compounds bearing a carbonyl group at ortho position to an internal alkyne. The methodology does not require transition-metal catalysts and moreover it is general for the preparation of wide range of benzo-annelated heterocycles, naphthalenes and benzenes.     

Synthesis of condensed heterocycles via cyclopropylimine rearrangement of cyclopropylazoles

Thermal cyclopropylimine rearrangement of cyclopropylazoles into condensed heterocycles and factors affecting the regioselectivity and conversion are reported. A method of conducting the reaction in the absence of solvents is developed. A series of 2-cyclopropylazoles, including novel examples, is synthesized and their transformations into the corresponding condensed heterocyclic compounds (2,3-dihydro-1H-pyrroles and 6,7-dihydro-5H-pyrrolo[2,1-b]thiazolium salts) are studied.     

A new, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines, 4H-pyrimido[1,2-a]pyrimidines, and 4H-pyrazino[1,2-a]pyrimidines

A new, one-pot and three-component synthesis of 4H-pyrido[1,2-a]pyrimidines, 4H-pyrimido[1,2-a]pyrimidines, and 4H-pyrazino[1,2-a]pyrimidines is described. The reactive 1:1 zwitterionic intermediate, formed by the addition of isocyanides to dialkyl acetylenedicarboxylates, was trapped by N-(2-heteroaryl)amides to yield a ketenimine intermediate, which was cyclized and then rearranged under the reaction conditions to afford the title compounds under mild reaction conditions in good yields. Single-crystal X-ray analysis conclusively confirms the structure of the obtained bridgehead bicyclic 6-6 heterocyclic compounds.     

rac-BINAP-PdCl2 catalyzed Heck reactions of 3-formylquinolin-2-yl chlorides with methyl acrylate: synthesis of methyl 3-(3-formylquinolin-2-yl) acrylates

rac-BINAP-PdCl₂ catalytic system catalyzed Heck reaction of 3-formylquinolin-2-yl chlorides with methyl acrylate in DMA is described to the synthesis of methyl 3-(3-formyl-quinolin-2-yl)-acrylates, in good to excellent yields. The reaction could be also extended with other activated alkenes to afford Heck products. Fused-benzene ring in heterocyclic and carbocyclic moieties was found to enhance the yields.