Heteroacyl azides as acylating agents for aromatic or heteroaromatic amines

The possibility of formation of substituted heterocyclic amides from heteroacyl azides and aromatic or heteroaromatic amines was investigated. Although acylation proceeded in some cases under mild reaction conditions, formation of N,N′-disubstituted ureas was the main process at elevated temperatures.     

Cyclic polycarbene ligands with crown ether structure

The cyclization reaction of coordinated β‐functional phenyl isocyanides was used to generate coordinated anellated N‐heterocyclic carbenes. Coordinated 2‐trimethylsiloxyphenyl isocyanide reacts, after Si O bond cleavage, to yield a complex with a coordinated benzoxazol‐2‐ylidene ligand. The cyclization reaction of coordinated 2‐aminophenyl isocyanide, obtained in situ from 2‐azidophenyl isocyanide, yields the coordinated benzimidazol‐2‐ylidene. Both ylidenes can be alkylated at the nitrogen atoms. Attempts to generate four benzimidazol‐2‐ylidenes at Pt^II and to bridge them by N‐alkylation leading to a crown ether‐like ligand with carbene donors are presented here. Free N‐heterocyclic carbenes derived from benzimidazole with large N‐substituents exist as monomers while they dimerize to dibenzotetraazafulvalenes when substituted with sterically less‐demanding substituents at the ring nitrogen atoms. A chemical equilibrium between the monomeric carbene and its dimerized enetetraamine exists for the N,N′‐isopropyl substituted derivative. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:540–549, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10099     

Novel (N‐heterocyclic carbene)Pd(pyridine)Br2 complexes for carbonylative Sonogashira coupling reactions: Catalytic efficiency and scope for arylalkynes,alkylalkynes and dialkynes

New N,N′‐substituted imidazolium salts and their corresponding dibromidopyridine–palladium(II) complexes were successfully synthesized and characterized. Reactions of palladium bromide with the newly synthesized N,N′‐substituted imidazolium bromides ( 2a and 2b ) in pyridine afforded the corresponding new N‐heterocyclic carbene pyridine palladium(II) complexes ( 3a and 3b ) in high yields. Their single‐crystal X‐ray structures show a distorted square planar geometry with the carbene and pyridine ligands in trans position. Both complexes show a high catalytic activity in carbonylative Sonogashira coupling reactions of aryl iodides and aryl diiodides with arylalkynes, alkylalkynes and dialkynes.     

An efficient one-pot synthesis of N,N′-disubstituted phenylureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid

We have developed an efficient one-pot method for the microwave-assisted synthesis of ureas and carbamates via a proposed Lossen rearrangement. Herein we report the first examples of the direct conversion of benzoyl chlorides into N,N′-disubstituted ureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid as reagent. Using our general method, we have produced 11 examples of N,N′-disubstituted phenylureas in yields up to 95% using various substituted anilines, and primary and secondary amines. Additionally, we were able to generate a series of N-aryl carbamates in moderate yields using primary, secondary and tertiary alcohols.     

Adsorption of some functionalized aliphatic compounds on plasma-grown thin-film aluminium and magnesium oxides

A study of the inelastic electron tunnelling (IET) spectra of N,N-diethyl-1,2-diaminoethane, N,N′-diethyl-1,2-diaminoethane, N,N′-dimethyl-1,2-diaminoethane, N,N,N′,N′-tetraethyl-1,2-diamino-ethane and N,N,N′,N′-tetramethyl-1,2-diaminoethane, shows all five systems to form five-membered chelate structures with both nitrogen atoms present in the adsorbate acting as Lewis donors at the same cation on either aluminium oxide or magnesium oxide. The IET spectra for the N-ethyl-2-aminoethanol, N,N-diethyl-2-aminoethanol and N,N-dimethyl-2-aminoethanol also examined indicate that similar alkoxy-amino chelated structures are formed with these adsorbates. For the aminoethanols adsorption—chelation appears to involve adsorbate deprotonation and hydroxyl depletion of the oxide surfaces involved with concomitant binding of the nitrogen atom present to the surface metal ion involved in alkoxide formation.     

2′‐Deoxy‐7‐propynyl‐7‐deaza­adenosine: a DNA duplex‐stabilizing nucleoside

In the title compound, 2′‐deoxy‐7‐propynyl‐7‐deaza­adenosine, C₁₄H₁₆N₄O₃, the torsion angle of the N‐glycosylic bond is anti [χ = −130.7 (2)°]. The sugar pucker of the 2′‐deoxy­ribo­furanosyl moiety is C2′‐endo–C3′‐exo, ²T₃ (S‐type), with P = 185.9 (2)° and τ_m = 39.1 (1)°, and the orientation of the exocyclic C4′—C5′ bond is −ap (trans). The 7‐substituted propynyl group is nearly coplanar with the heterocyclic base moiety. Mol­ecules of the nucleoside form a layered network in which the heterocyclic bases are stacked head‐to‐tail with a closest distance of 3.197 (1) Å. The crystal structure of the nucleoside is stabilized by three inter­molecular hydrogen bonds of types N—H⋯ O, O—H⋯ N and O—H⋯ O.     

Unprecedented Double aza‐Michael Addition within a Sapphyrin Core

A novel sapphyrin derivative was obtained from the reaction between a free‐base sapphyrin and dimethyl acetylenedicarboxylate (DMAD). The formation of the new compound involved a double aza‐Michael addition of two pyrrolic NH groups to a DMAD molecule, with the formation of a disubstituted ethano bridge. The NMR spectral data reveal a product with an unsymmetrical structure; DFT calculations provided support for a structure in which the ethano bridge links two adjacent pyrrole units. The present study provides a seemingly unprecedented example of an N,N′‐dinucleophile reacting with DMAD to form a heterocyclic compound in which the two N‐atoms are linked to the two sp³ carbon atoms derived from a substituted acetylene.     

草酰胺配体的微波合成

在微波辐照下, 分别由苯胺、取代苯胺和草酸通过无溶剂法反应, 合成出N,N′-二(苯基)草酸二酰胺和N,N′-二(取代苯基)草酸二酰胺, 利用¹H NMR, MS和元素分析对其结构进行了表征. 研究表明, 增加辐照功率选择合适的辐照时间有利于产物收率的提高, 甲基或氯单取代的苯胺得率高于苯胺, 增加固液两相的接触面积可大大提高产物的收率.     

Photopolymerization V. Unsensitized solution photocyclopolymerization of N,N ′-alkylenebismaleimides

The term, “photopolymerization,” is defined as a polymerization process in which every chain-propagating step involves a photo-chemical reaction. This type of polymerization is exemplified by the unsensitized solution photocyclopolymerization of several N,N ′-alkylenebismaleimides, substituted at the double bond. N,N ′-Alkylenebismaleimides substituted with a bromine atom or two methyl groups at their double bond produce high polymeric products upon ultraviolet irradiation in solution. A general reaction scheme for the photopolymerization is proposed. Kinetic measurements show that the solution photopolymerization of substituted bismaleimides is a multistep reaction.     

A new and practical PIFA-promoted olefin amidohydroxylation: six- versus five-membered ring formation

A novel access to the isoindolinone and isoquinolin-2-one skeletons from adequately substituted aromatic precursors is described. The key intramolecular cyclization step was performed by the action of phenyliodine(III)bis(trifluoroacetate) (PIFA) on the corresponding vinyl or allyl substituted N-(p-methoxyphenyl)benzamide derivatives leading to the heterocyclic compounds through 5-exo-trig and 6-exo-trig processes, respectively.     

Synthesis of derivatives of pyrido[3′,2′:4,5]furo[3,2-c]isoquinoline heterocyclic system

An approach to the synthesis of derivatives of new heterocyclic system, pyrido[3′,2′:4,5]-furo[3,2-c]isoquinoline, was suggested. A condensation reaction of substituted 3-cyanopyridin-2(1H)-ones with methyl 2-(chloromethyl)benzoate and subsequent treatment of the condensation product with potassium tert-butoxide leads to substituted pyrido[3′,2′:4,5]furo[3,2-c]-isoquinolin-5(6H)-ones. Similarly, a condensation reaction of substituted 3-cyanopyridin-2(1H)-ones with 2-(chloromethyl)benzonitrile and subsequent treatment of the condensation product with potassium tert-butoxide gives substituted 5-aminopyrido[3′,2′:4,5]furo[3,2-c]-isoquinolines.     

Aminoacids in the synthesis of heterocyclic systems. The synthesis of methyl 2-acetylamino-3-dimethylaminopropenoate and 2-(N-methyl-N-trifluoroacetyl)amino-3-dimethylaminopropenoate and their application in the synthesis of heterocyclic compounds

Methyl (Z)-2-acetylamino-3-dimethylaminopropenoate (3) was prepared from N-acetylglycine (1), which was converted with N,N-dimethylformamide and phosphorus oxychloride into 4-dimethylaminomethylene-2-methyl-5(4H)-oxazolone (2), followed by treatment with methanol in the presence of potassium carbonate, into 3. The compound 3 was shown to be a versatile reagent in the synthesis of various heterocyclic systems. With N-nucleophiles, such as heterocyclic amines 4, either methyl 2-acetylamino-3-heteroarylaminopropenoates 5 or fused pyrimidinoncs 6 were formed, dependent on the reaction conditions and/or heterocyclic substituents: C-nuclcophiles with an active or potentially active methylene group, such as 1,3-dicarbonyl compounds 7, 8 and 9, substituted phenols 10a,b, naphthols 11, 12a-c, and substituted coumarin 13a, afforded substituted pyranones 20 and 22, and fused pyranones 21, 23–26. The nitrogen containing heterocycles 14–19 produced pyranoazines 27–31 and pyranoazole 32. In all of these systems the acetylamino group is attached at position 3 of the newly formed pyranone ring. The orientation around the double bond for methyl (Z)-2-(N-methyl-N-trifluo-roacetyl)-3-dimethylaminopropenoate (36) was established by X-ray analysis.     

Synthesis and characterization of thermally stable poly-N, N′-arylenebismaleimide

Three N,N′-arylenebismaleimides, viz. N,N′-m-phenylenebismaleimide, N,N′-p-phenylenebismaleimide and N,N′-benzidinebismaleimide, were prepared and polymerized in toluene using benzoyl peroxide (BPO) as initiator. The polymers obtained were characterized on the basis of elemental analysis and IR spectra. The polymers are insoluble in common organic solvents. The thermal behaviour of these polymers was studied by DTA and TG methods and the kinetic parameters order of reaction and activation energy were estimated.     

A simple and convenient synthesis of substituted furans and pyrroles by CuCl2-catalyzed heterocyclodehydration of 3-yne-1,2-diols and N-Boc- or N-tosyl-1-amino-3-yn-2-ols

A simple and economical synthesis of substituted furans and pyrroles, by ligand-free CuCl₂-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and N-Boc- or N-tosyl-1-amino-3-yn-2-ols, respectively, is presented. Reactions are carried out in MeOH at 80-100 °C for 1-24 h and afford the corresponding heterocyclic derivatives in 53-99% isolated yields.     

Synthesis of some novel derivatives of 1,10‐phenanthroline

The synthesis is described of a set of new N‐heterocyclic compounds which are derivatives of 1,10‐phenanthroline. The compounds are designed to be general purpose chelating agents which could function as tri‐, tetra‐ or hexadentate ligands with transition metal ions. Fused‐ring molecular components have been included in the design of the compounds so that they may function as binding agents to DNA through intercalation. This includes the synthesis of substituted derivatives of pyrazino[2,3‐f][1,10]phenanthroline and dipyrido[3,2‐a:2′3′‐c]phenazine.     

Synthesis and transformations of bis(polychloroethylideneaminosulfonyl)- and bis(polychloroethylideneaminosulfonyl)-substituted derivatives of biphenyl, diphenyl oxide, and diphenylmethane

Reactions of N,N,N′,N′-tetrachlorobiphenyl-4,4′-disulfonamide, 4,4′-methylenebis(N,N-dichlorobenzenesulfonamide), and 4,4′-oxybis(N,N-dichlorobenzenesulfonamide) with 1,2-dichloroethylene and trichloroethylene open convenient synthetic approach to highly electrophilic bissulfony limines of dichloroacetic aldehyde and chloral: N,N′-bis(polychloroethylidene)biphenyl-4,4′-disulfonamides, 4,4′-methylenebis[N-(polychloroethylidene)benzenesulfonamides] and 4,4′-oxybis[N-(polychloroethylidene)benzenesulfonamides]. The synthetic opportunities of the bisazomethines obtained were demonstrated by examples of their reactions with water, methanol, chloroacetamide, and toluene where products of O-, N-nucleophiles addition to the azomethine bond and products of C-amidoalkylation of aromatic compound with imines were formed.     

N-Arylimidazole synthesis by cross-cycloaddition of isocyanides using a novel catalytic system

A direct catalytic synthesis of N-arylimidazoles starting from the corresponding N-arylformamides and N-formylglycine esters is described. Application to different aryl substituted electron-withdrawing and -donating groups provided the analogous heterocyclic compounds in very high yields. The use of copper(I) oxide/proline catalysts allowed the reactions to proceed at room temperature. The first synthesis of N-arylimidazole bearing carbohydrate moieties is also described.     

Nonglycoside analogs of nucleotides

N¹-(2′,3′-Dihydroxypropyl)uracil, -thymine, -cytosine, and N⁹-(2′,3′-dihydroxypropyl)adenine were synthesized by alkylation of nucleic bases with 2,3-O-isopropylideneglycerol chlorohydrin, subsequent separation of the resulting mixtures, and removal of the protective groupings. Phosphorylation of these compounds or of their selectively substituted derivatives gave 2′(3′)-monophosphates, which were converted to 2′,3′-cyclophosphates by reaction with N,N′-dicyclohexylcarbodiimide. Thionation of the corresponding cytosine derivatives gave N¹-(2′,3′-dihydroxypropyl)-4-thiouracil and its 2′(3′) phosphate.     

Stereocontrolled synthesis of 3-amino-2-hydroxyalkyl diphenylphosphine oxides mediated by chiral azetidinium salts and epoxyamines

The stereocontrolled synthesis of amino hydroxyalkyl diphenylphosphine oxides has been achieved starting from (2S,3S)-N,N-dibenzyl-3-hydroxy-2-methylazetidinium bromide or (1R),[1′(S)-(dibenzylamino)ethyl]oxirane. The regioselective ring opening of both heterocyclic systems at the less substituted carbon atom with phosphorus nucleophiles proceeded with full stereochemical integrity.     

Stable Mesoionic N‐Heterocyclic Olefins (mNHOs)

We report a new class of stable mesoionic N‐heterocyclic olefins, featuring a highly polarized (strongly ylidic) double bond. The ground‐state structure cannot be described through an uncharged mesomeric Lewis‐structure, thereby structurally distinguishing them from traditional N‐heterocyclic olefins (NHOs). mNHOs can easily be obtained through deprotonation of the corresponding methylated N,N′‐diaryl‐1,2,3‐triazolium and N,N′‐diaryl‐imidazolium salts, respectively. In their reactivity, they represent strong σ‐donor ligands as shown by their coordination complexes of rhodium and boron. Their calculated proton affinities, their experimentally derived basicities (competition experiments), as well as donor abilities (Tolman electronic parameter; TEP) exceed the so far reported class of NHOs.