A general synthesis of N-aryl- and N-alkyl-2-aminobenzoxazoles

An efficient and practical synthetic procedure is described for the preparation of a variety of N-substituted aryl- and alkyl-2-aminobenzoxazoles. This new method offers broad utility and provides desired products in good to excellent yield. The title compounds are formed in a one-pot, two step reaction sequence that is safe and operationally straightforward.     

Palladium complexes of N-aryl-2-pyridylamines

Palladium complexes of N-phenyl-2-pyridylamine (4) and dipyridylamine substrates (7, 11) have been studied. Due to the coordination ability of the pyridine-nitrogen atoms, the pyridyl substrates, 4, 7, 11 were subjected to Pd(OAc)₂ complexations and a number of N-aryl-2-pyridylamine Pd complexes (13-17) were isolated and characterised, in particular by NMR and ESI-MS. A new method for the preparation of the acetato-bridged six-membered ring palladacycle complex (13) of 4 is reported. The dipyridyl amines 7, 11 formed cis/trans bis-dentate acetato-bridged dimeric Pd₂Lig₂(OAc)₂ (14a,b/16a,b) and Pd₃Lig₂(OAc)₄ complexes (15a,b/17a,b). The N-aryl-2-pyridylamine substrates (4, 7, 11) were prepared by oxidative nucleophilic substitution, by 1,3-cycloaddition reaction or by Buchwald amination.     

A diastereoselective aza-Diels-Alder reaction of N-aryl-1-azadienes derived from α-amino acids with enamines

A diastereoselective inverse electron demand aza-Diels-Alder reaction of N-aryl-1-azadienes derived from α-amino acids is accomplished using enamine dienophiles. Activation with ytterbium triflate of these azadienes affords dimeric structures through aza-Diels-Alder reaction, where the alkene double bond of 1-azadienes also adopts the role of dienophile. An asymmetric synthesis of functionalised 1,4,5,6-tetrahydropyridine compounds derived from α-amino acids using an optically active enamine is reported.     

Mild, convenient and versatile Cu-mediated synthesis of N-aryl-2-imidazolidinones

A mild, general, convenient and practical methodology for the selective copper-mediated mono N-arylation of unprotected 2-imidazolidinone was developed. Strong electron-donating groups and free hydroxy and amino groups on the aryl iodide substrates were well tolerated. The use of n-butanol as the solvent for the copper-catalysed mono-arylation of 2-imidazolidinone is unprecedented.     

A short and efficient synthesis of N-aryl- and N-heteroaryl-N-(arylalkyl)piperazines

A new synthesis of N-aryl- and N-heteroaryl-N^′-(arylalkyl)piperazines using palladium-catalyzed amination of aryl bromides and heteroaryl chlorides with mono N-benzyl- or N-(arylethyl)piperazines is reported. Most coupling processes proceed in high yield and good selectivity using either diadamantyl-n-butylphosphine (1), 2-(dicyclohexylphosphino)-2^′-(N,N-dimethylamino)biphenyl (2), or 2-(di-tert-butylphosphino)biphenyl (3) as ligand. Applying an automated parallel synthesizer the preparation of a small library of potentially bioactive compounds is easily achieved.     

Synthesis of N-aryl-2,2,2-trifluoroacetimidoyl piperazinylquinolone derivatives and their antibacterial evaluations

N-substituted trifluoroacetimidoyl chlorides were used for the synthesis of new piperazinylquinolone derivatives. These reactions provided N-aryl-2,2,2-trifluoroacetimidoyl piperazinylquinolone derivatives in good yields. Two selected compounds were evaluated for their antibacterial activities. These compounds displayed good antibacterial activities.     

Dihydropyrimidines and related structures. I. N2-substituted 2-pyrimidinamines and dihydro-2-pyrimidinamines by reaction of phenylbutenones and monosubstituted guanidines

The reactions of monosubstituted guanidines 2 with phenylbutenones 7 and 10 exclusively yield N²-substituted 2-pyrimidinamines 8 and 9 . The structure of the reaction products is proved and their differing stability is discussed. Action of methyl- and benzylguanidine respectively ( 2b, c ) on 4-phenyl-3-buten-2-one ( 7 ) and of 2c on l-phenyl-2-buten-1-one ( 10 ) under atmospheric oxygen affords aromatic N²-substituted 2-pyrimidinamines 9b and c . The dihydropyrimidines 8b and c, probable intermediates of the reactions, could not be isolated. In contrast, heating of arylguanidines 2d , e with 7 leads to stable dihydropyrimidinarnines 8d and e, which can be isolated as bases. Addition of methanol to 8d yields 6-methoxy-2-pyrimidinamine 11d , boiling of 8d in DMF affords 9d . Under nitrogen, guanidine adds to 7 to yield aminopyrimidinol 13a , which is transformed by heating in benzene into pyrimidine 9a . The low stability of 8a-c is attributed to their strong basicity, the greater stability of 8d and e to their lower basicity. The structural formulae of 8d , e and 9b-d and their salts respectively were established partly ( 8e ) by nmr and partly ( 9b-d ) by comparison of the corresponding picrates with authentic samples [17].     

Copper catalyzed oxidative cross-coupling of aromatic amines with 2-pyrrolidinone: a facile synthesis of N-aryl-γ-amino-γ-lactams

Synthesis of N-aryl-γ-amino-γ-lactams by oxidative coupling of aromatic amines with 2-pyrrolidinone using catalytic amount of CuO nanoparticles is described. The procedure has broad substrate scope, good yields, complete regioselectivity and catalyst recyclability.     

New reaction of ethenetetracarbonitrile with N-arylisoindolines

N-Arylisoindolines 1a-i react with ethenetetracarbonitrile 2 in aerated benzene by formation of [3-(2-aryl-3-dicyanomethylene-2,3-dihydro-1H-isoindol-1-ylidene)-2-aryl-2,3-dihydro-1H-isoindol-1-ylidene]propanedinitriles 8a-i (20-36%), N-aryl-3-dicyanomethylene-isoindol-2-ones 9a-i (15-21%) and N-arylphthalimides 10a-i (4-9%) as well as 1,1,2,2-tetracyanoethane 11 (35-55%). The structure of 8d has been unambiguously confirmed by a single crystal X-ray structure analysis. A rationale for the formation of products 8-11 is presented.     

Synthesis and tautomeric structure of 2-[N-aryl-2-oxo-2-arylethanehydrazonoyl]-6-methyl-4(3H)-pyrimidinones

Two series of 2-(N-aryl-2-oxo-2-arylethanehydrazonoyl)-6-methyl-4(3H)-pyrimidinones 11 (12) were prepared by coupling of diazotized anilines with 2-(aroylmethylene)-1,2-dihydro-6-methyl-4(3H)-pyrimidinones 2 (3). The spectral data of such compounds together with their 3-methyl analogs 13 (14) indicated that they exist predominantly in the hydrazone tautomeric form.     

Palladium-catalyzed cross-coupling reaction of aryldioxaborolane with 2-bromo-N,N-dimethylacetamide

A Suzuki-type cross-coupling of aryldioxaborolane with 2-bromo-N,N-dimethylacetamide in the presence of a catalytic amount of tricyclohexylphosphine as the ligand and hydroquinone as the free-radical scavenger has been demonstrated as a convenient and simple way for the synthesis of α-arylacetamide.     

Synthesis of fused thiazolo[3,2-a]pyrimidinones: N-aryl-2-chloroacetamides as doubly electrophilic building blocks

2-Chloro-N-phenylacetamide and N-(benzo[d]thiazol-2-yl)-2-chloroacetamide are doubly electrophilic building blocks for the formation of ring annulated thiazolo[3,2-a]pyrimidinone products. This synthetic route involves formation of the title compound in acceptable product yields by the elimination of the by-product, aniline/2-aminobenzothiazole. Analytical and spectral studies, as well as single crystal X-ray data on the representative compound 6c confirmed the structure of all the reaction products.     

N-Bromosuccinimide-mediated reaction of cyclic styrenes with chloramine-T

A facile route toward substituted allylic sulfonamides 3 is developed from the N-bromosuccinimide (NBS)-mediated allylic amination of cyclic styrenes 2 with chloramine-T (1a). Skeleton 2 is prepared by Grignard addition of cyclic ketones with different arylmagnesium bromides in THF followed by dehydration of the resulting tertiary alcohols with BF₃·OEt₂ in CH₂Cl₂. The synthetic route obtained moderate yields from the one-step operation and the key structures of skeleton 3 were confirmed by X-ray crystallographic analysis.     

The reaction of N-tosyl imines with heteroaromatic compounds: a new access to triheteroarylmethanes

Useful triheteroarylmethanes were prepared by the double Friedel-Crafts reaction of a wide variety of aromatic N-tosyl imines with furan, thiophene, and pyrrole in the presence of Cu(OTf)₂ and Montmorillonite K-10 clay catalysts.     

Synthesis of N,N-dialkylaminobenzonitriles and halo-(N,N-dialkyl)benzamidines by reaction of halobenzonitriles with lithium amides

3- and 4-N,N-Dialkylaminobenzonitriles and 4-chloro-(N,N-dialkyl)benzamidines were isolated by reacting 4-chlorobenzonitrile with hindered lithium amides under thermodynamic (0 °C) and kinetic control conditions (−78 °C), respectively. As previously reported, a benzyne mechanism seems to be confirmed since N,N-dialkylaminobenzonitriles are formed. Only benzamidines were isolated in fair to high yields at both 0 °C and −78 °C with non-hindered lithium amides. Exploitation and mechanistic rationale of the reaction of different halobenzonitriles are also reported.     

A novel three-component reaction for the synthesis of N-cyclohexyl-3-aryl-quinoxaline-2-amines

Ferric perchlorate catalyzes the three-component condensation reaction of o-phenylenediamine, aromatic aldehydes, and cyclohexyl isocyanide to afford the corresponding N-cyclohexyl-3-aryl-quinoxaline-2-amines in good yields.     

Synthesis of N-aryl-3-(arylimino)-3H-indol-2-amines via hypervalent iodine promoted oxidative diamination of indoles

A direct and fast oxidative diamination of substituted indoles with anilines was realized by using 1-fluoro-1,2-benziodoxol-3(1H)-one under mild conditions. This protocol could provide a wide range of synthetically valuable N-aryl-3-(arylimino)-3H-indol-2-amine derivatives under peroxide-free conditions within 30?min in up to 91% yields.     

Hydrogen bonding and halogen bonding co-existing in the reaction of heptafluorobenzyl iodide with N,N,N,N-tetramethylethylene diamine

Two novel assembling systems 3 and 4, with the structures of C₆F₅CF₂⁻?H⁺N(Me)₂CH₂CH₂(Me₂)N⁺H?⁻CF₂C₆F₅ and C₆F₅CF₂I?N(Me)₂CH₂CH₂(Me)₂N?ICF₂C₆F₅, respectively, have been generated from the solution of heptafluorobenzyl iodide 1 and N,N,N^′,N^′-tetramethylethylenediamine 2 in dichloromethane. Their structures have been characterized by X-ray diffraction analysis, NMR and IR spectroscopy. Intermolecular N?I halogen bond and F?H hydrogen bond are revealed to be the driving forces for their formation.