Pyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxides. Sulfur dioxide analogs of pteridines

Several pyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxide derivatives have been synthesized for the first time by condensation of suitable 4,5-diamino-1,2,6-thiadiazine 1,1-dioxides and symmetrical 1,2-dicarbonyl compounds. Structures of these compounds have been characterized by their elementary analyses, ¹H-nmr and uv spectra as well as their pK_a values. The most striking differences between this series and the corresponding pteridines are discussed.     

Selective Bromination of Pyrido[2,3-c][1,2,6]thiadiazine 2,2-Dioxides

Bromination with NBS of 4-aminopyrido[2,3-c][1,2,6] thiadiazine 2,2-dioxides provides an efficient and selective method for the synthesis of the corresponding 6-bromo derivatives.     

Facile Route to Novel Pyrazolo[3,4‐d]pyrimidine,Imidazo[1,2‐b] pyrazole,Pyrazolo[3,4‐d][1,2,3]triazine,Pyrazolo[1,5‐c][1,3,5]triazine and Pyrazolo[1,5‐c][1,3,5]thiadiazine Derivatives

A regioselective synthesis of novel pyrazolo[3,4‐d]pyrimidines, imidazo[1,2‐b]pyrazoles, pyrazolo[3,4‐d][1,2,3]triazine, pyrazolo[1,5‐c][1,3,5]triazine and pyrazolo[1,5‐c][1,3,5]thiadiazine incorporating a thiazole moiety was described via the reactions of the versatile, readily accessible 5‐amino‐3‐(phenylamino)‐N‐(4‐phenylthiazol‐2‐yl)‐1H‐pyrazole‐4‐carboxamide ( 1 ) with each of DMF‐DMA, phenylisothiocyanate, chloroacetyl chloride, phenacyl bromide, benzoylisothiocyanate and formalin, respectively. All structures of the newly synthesized compounds were elucidated by elemental analysis and spectral data.     

An interesting synthesis of thieno[2,3‐d][1,2,3]thiadiazole via decomposition/recyclization of 3‐methoxycarbonyl‐1H‐thieno‐[2,3‐e][1,3,4]thiadiazine 4,4‐dioxide

Attempted hydrolysis of the ester of 3‐methoxycarbonyl‐1H‐thieno[2,3‐e][1,3,4]thiadiazine 4,4‐dioxide ( I ) under acidic conditions gave the ring‐contracted thieno[2,3‐d][1,2,3]thiadiazole ( V ) instead of the expected carboxylic acid. In addition to a discussion of the reaction, a plausible mechanism is presented.     

Synthesis of Some 7H‐s‐Triazolo[3,4‐b]‐1,3,4‐thiadiazine Derivatives

The cyclization of 1‐amino‐2‐mercapto‐5‐[5‐methyl‐1‐(4‐methylphenyl)‐1,2,3‐triazol‐4‐yl]‐1,3,4‐triazole with various α‐haloketone in absolute ethanol yields 7H‐3‐[5‐methyl‐1‐(4‐methylphenyl)‐1,2,3‐triazol‐4‐yl]‐6‐substituted‐s‐triazolo[3,4‐b]‐1,3,4‐thiadiazines and their structures are established by elemental analysis, MS, IR and ¹H NMR spectral data.     

Exploration of the Photodegradation of Naphtho[2,3‐g] quinoxalines and Pyrazino[2,3‐b]phenazines

Nitrogen‐containing polycyclic aromatic hydrocarbons are very attractive compounds for organic electronics applications. Their low‐lying LUMO energies points towards a potential use as n‐type semiconductors. Furthermore, they are expected to be more stable under ambient conditions, which is very important for the formation of semiconducting films, where materials with high purity are needed. In this study, the syntheses of naphtho[2,3‐g]quinoxalines and pyrazino[2,3‐b]phenazines is presented by using reaction conditions, that provide the desired products in high yields, high purity and without time‐consuming purification steps. The HOMO and LUMO energies of the compounds are investigated by cyclic voltammetry and UV/Vis spectroscopy and their dependency on the nitrogen content and the terminal substituents are examined. The photostability and the degradation pathways of the naphtho[2,3‐g]quinoxalines and pyrazino[2,3‐b]phenazines are explored by NMR spectroscopy of irradiated samples affirming the large influence of the nitrogen atoms in the acene core on the degradation process during the irradiation. Finally, by identifying the degradations products of 2,3‐dimethylnaphtho[2,3‐g]quinoxaline it is possible to track down the most reactive position in the compound and, by blocking this position with nitrogen, to strongly increase the photostability.     

1‐Hydroxy‐1H‐benzo[d][1,2,6]oxazaborinin‐4(3H)‐one

The structure of the title compound, C₇H₆BNO₃, a new boron heterocycle, prepared by the condensation of (2‐ethoxycarbonylphenyl)boronic acid and hydroxylamine, reveals the specific mode of intramolecular condensation between a phenylboronic acid and an ortho hydroxamic acid substituent. The crystal structure shows that dehydration occurs to form a planar oxazaborinine ring possessing both phenol‐like B—O—H and lactam functional groups. In the extended structure, intermolecular hydrogen bonding generates a 14‐membered ring. To our knowledge, this is the first crystal structure determination involving a six‐membered ring that exhibits consecutive B—OH, O, NH, and C=O functional groups.     

Synthesis of some pyrazolo[1,5‐c][1,3]benzoxazines and a new 5H‐pyrazolo[1,5‐c][1,3,2]benzoxazaphosphorine ring system

Condensations of 5‐(2‐hydroxyphenyl)pyrazoline 3a with 4‐carboxybenzaldehyde, glyoxylic acid and N,N‐carbonyldiimidazole leading to pyrazolobenzoxazine derivatives were studied. The observed diastere‐oselectivity is discussed. Reaction of 3a with Lawesson reagent gave rise to a new 5H‐pyrazolo[1,5‐c]‐[1,3,2]benzoxazaphosphorine heterocyclic system.     

Synthesis of 6‐Aminopropyl‐6H‐indolo[2,3‐b]quinoxaline Derivatives

A series of 6‐(3‐aminopropyl)‐6H‐indolo[2,3‐b]quinoxalines were synthesized with high yields by the reaction of 6‐(3‐chloropropyl)‐6H‐indolo[2,3‐b]quinoxaline and corresponding amines in presence of tetrabutylammonium iodide in boiling toluene or dimethylformamide at room temperature. It was found that boiling of 6‐(3‐chloropropyl)‐6H‐indolo[2,3‐b]quinoxaline in acetone with sodium iodide or in acetic acid lead to intramolecular cyclization product.     

A Novel Synthesis of Some 1,4‐Phenylene‐bis‐heterocyclic Derivatives and of Some Pyran,Pyrano[2,3‐c]pyrazole,and Pyrano[2,3‐d]pyrimidine Derivatives [1]

p‐Diacetyl benzene 1 undergoes bromination to afford p‐bromoacetyl phenacyl bromide 2 . Compound 2 reacts with twofold excess of malononitrile to afford 2‐{2‐[4‐(3,3‐Dicyanopropionyl)‐phenyl]‐2‐oxo‐ethyl}‐malononitrile 3 . Compound 3 could be cyclized to afford the 1,4‐phenylene‐bis‐furan derivative 4 . Compound 3 reacts also with a twofold excess of hydrazine hydrate and phenyl hydrazine under dry conditions at RT to afford the bis‐pyrazole derivatives 5a , 5b , respectively. The reaction of 5a , 5b with the same reagents in refluxing dioxane afforded the bis‐pyrazolopyridazine derivatives 7a , 7b , respectively. The azo coupling of compound 3 with arene diazonium salts afforded the bis‐pyrazole derivatives 9a , 9b , 9c . The β‐keto esters 10a , 10b react with benzaldehyde and malononitrile in a one pot synthesis to afford the pyran derivatives 11a , 11b . These latter compounds react with hydrazine hydrate and urea derivatives to afford the pyrano[2,3‐c]pyrazoles 15a , 15b and the pyrano[2,3‐d]pyrimidine derivatives 17a , 17b , respectively.     

An Efficient Synthesis and Antibacterial Activity of Pyrido[2,3‐d]Pyrimidine,Chromeno[3,4‐c]Pyridine,Pyridine, Pyrimido[2,3‐c]Pyridazine,Enediamines, and Pyridazine Derivatives

A series of Pyrido[2,3‐d]pyrimidine have been synthesized through a reaction of cyanoacetylurea derivatives with aromatic aldehydes or Arylidines. Reaction of compound 1 with aromatic arylidine derivatives or arylhydrazones gave Chromeno[3,4‐c]pyridine, Pyridine, Pyrimido[2,3‐c]pyridazine, Enediamines, and Pyridazine derivatives. All the synthesized compounds were confirmed by spectral studies and screened for their in antibacterial activity against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative) bacterial strains. All the compounds were weak to good active against the tested bacterial strains on comparing with the standard drug gentamicin.     

Synthesis,Structures, and Properties of Two Novel Supramolecular Architectures Constructed from [2,3‐f]Pyrazino[1,10]phenanthroline‐2,3‐dicarboxylic Acid

Two new compounds, [Ag(Hppdb)]_n ( 1 ) and {[Ag₂(Hppdb)₂(bpe)] · 5.5H₂O}_n( 2 ) [H₂ppdb = [2,3‐f]pyrazino[1,10]phenanthroline‐2,3‐dicarboxylic acid, bpe = trans‐1,2‐bis(4‐pyridyl)ethylene], were synthesized and characterized. In 1 , Hppdb^– ions link Ag^I cations to form an infinite 1D [–Ag–(Hppdb)–Ag–]_n chain, furthermore, the dimensionality is extended to 2D layers through synergistic π–π stacking, hydrogen‐bonding and weak Ag ··· O interactions. Correspondingly, the dimeric [(Ag)(Hppdb)]₂ subunits in 2 are connected by bpe ligands to generate a loop‐link‐shaped 1D chain motif, which is further joined through a R₂²(18)C–H ··· O hydrogen‐bonding ring to afford interesting diagonal/diagonal inclined catenation 2D + 2D → 3D supramolecular architectures. In addition, solid‐state properties such as photoluminescence and thermal stability of the two compounds were studied.     

New route to pyrimido[4,5‐ e][1,3,4]thiadiazine derivatives

5‐Bromo‐2‐chloro‐4‐methyl‐6‐(1‐methylhydrazino)pyrimidine is readily obtained from the recently reported 5‐bromo‐2,4‐dichloro‐6‐methylpyrimidine by treatment with methylhydrazine in chloroform. Treatment of this compound with carbon disulfide and several alkyl halides gave an intermediate which was successfully converted to its corresponding 3‐(alkylsulfanyl)‐7‐chloro‐1,5‐dimethyl‐1H‐pyrimido[4,5‐e][1,3,4]thiadiazine derivatives in basic acetonitrile. The latter compounds were reacted with secondary amines in boiling ethanol to afford the related 7‐amino derivatives.     

Synthesis of Imidazo[2,1‐b][2H‐1,3,4]thiadiazines and 1,2,4‐Triazolo[3,4‐b][2H‐1,3,4]thiadiazines

Imidazo[2,1‐b][2H‐1,3,4]thiadiazines were prepared by cyclization of 2‐amino‐5‐(4‐chlorophenyl)‐6H‐1,3,4‐thiadiazine with α‐haloketones. 1,2,4‐Triazolo[3,4‐b][2H‐1,3,4]thiadiazines were prepared by cyclization of 4‐amino‐5‐sulfanyl‐l,2,4‐triazoles with phenacyl bromides.     

Synthesis of [1,4]benzodioxino[2,3‐c and 2,3‐d]pyridazinones

Reaction of chloropyridazin‐3‐one 1, 5 and 10 with catechol in the presence of potassium carbonate gave the corresponding [1,4]benzodioxino[2,3‐e and/or 2,3‐d]pyridazinones 2, 7, 8 and 11 .     

Synthesis and Properties of 2,3‐Dihydro‐1H‐corannuleno[2,3‐cd]pyridine (=2,3‐Dihydro‐1H‐dibenzo[1,10 : 6,7]fluorantheno[3,4‐cd]pyridine) Derivatives: Heterocyclic peri‐Anellated Corannulenes

The anellation of a 6‐membered ring to the 2,3‐position of corannulene (=dibenzo[ghi,mno]fluoranthene; 1 ) leads to curved aromatic compounds with a significantly higher bowl‐inversion barrier than corannulene (see Fig. 1). If the bridge is −CH₂−NR−CH₂−, a variety of linkers can be introduced at the N(2) atom, and the corresponding curved aromatics act as versatile building blocks for larger structures (see Scheme). The locked bowl, in combination with an amide bond (see 9 and 10 ), gives rise to corannulene derivatives with chiral ground‐state conformations, which possess the ability to adapt to their chiral environment by shifting their enantiomer equilibrium slightly in favor of one enantiomeric conformer. Rim annulation of corannulene seems to display a significantly lower electron‐withdrawing effect than facial anellation on [5,6]fullerene‐C₆₀‐I_h, as determined by an investigation of the basicity at the N‐atom of CH₂−NR−CH₂ (see 4 vs. 15 in Fig. 2).     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 22 Dibenzo[f,h]benzothieno[2,3‐c]quinoline,dibenzo[f,h]benzothieno[2,3‐c][1,2,4]triazolo[4,3‐a]quinoline and dibenzo[f,h]naphtho[2′,1′:4,5]thieno[2,3‐c]quinoline

Photocyclization of 3‐chloro‐N‐(9‐phenanthryl)benzo[b]‐thiophene‐2‐carboxamide ( 3 ) and 3‐chloro‐N‐(9‐phenanthryl)‐naphtho[1,2‐b]thiophene‐2‐carboxamide ( 10 ) yielded dibenzo[f,h]benzothieno[2,3‐c]‐quinolin‐10(9H)‐one ( 4 ) and dibenzo[f,h]naphtho[2′,1′:4,5]thieno[2,3‐c]quinolin‐10(9H)‐one ( 11 ), respectively. Further elaboration of the lactams provided three novel unsubstituted new ring systems.     

Synthesis of Cyano‐pyrrolo[1,2‐a][1,10]phenanthroline Derivatives Using a Multicomponent Condensation

1,10‐Phenanthroline reacts with malonitrile and aldehydes in the presence of isocyanides as domino‐Knoevenagel‐nucleophilic cycloaddition for generation of a new class of 10‐(aryl)‐11‐(alkyl‐ or arylamino‐)pyrrolo[1,2‐a][1,10]phenanthroline‐9‐carbonitrile compounds in excellent yield. All compounds are fully characterized with one structurally authenticated by a single X‐ray diffraction study.