New heterocycles from 8‐hydroxyquinoline via dipolar 1,3‐cycloadditions: Synthesis & biological evaluation

Diarylnitrilimine and arylnitriloxide dipoles react with two 8‐hydroxyquinoline substrates to give respectively pyrazolinic and isoxazolinic derivatives. The structure of these new heterocycles was established on the basis of their spectroscopic data and by chemical methods. The inhibition activity of one of these heterocycles was evaluated in vitro against 8 pathogenic μ‐organisms.     

Metallacyclopentadienes and related heterocycles via 1,1‐organoboration of alkyn‐1‐ylmetal compounds

Metallacyclopentadienes (metalloles) containing M = Si, Ge, Sn, Pb, Ti, Pt can be prepared by 1,1‐organoboration of alkyn‐1‐ylmetal compounds L_nM CC R¹(R¹ = H, alkyl, aryl, silyl, etc; L depends on M, and can be hydrogen, alkyl, aryl, Cl, Br, amino groups, a chelating diphosphane, and one or more L can be again alkynyl groups). These reactions proceed via activation of the M C bond(s) by an electron‐deficient triorganoborane BR₃ (R = alkyl, aryl; non‐cyclic, monocyclic, bicyclic, and tricyclic boranes), at first intermolecular and then intramolecular. In the course of these reactions, the M C bonds are cleaved, zwitterionic alkynylborate‐like intermediates are formed, in which the metal‐containing fragments are coordinated side‐on to the CC bonds. In most cases, the 1,1‐organoboration reactions tolerate various functional groups at the alkyne as well as at the metal. The characterization of intermediates and final products by X‐ray structural analysis and by multinuclear magnetic resonance spectroscopy (NMR) is documented and described. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:188–208, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20222     

Synthesis of Some New Pyrazole,Pyrimidine, Pyridazine,and Their Fused Derivatives from 3‐Oxo‐3,N‐diphenylpropionamide

The title compounds were obtained from the reactions of 3‐oxo‐3,N‐diphenylpropionamide 3 with dimethylformamide dimethylacetal followed by hydrazine to afford the pyrazole 7 , condensation with benzaldehyde followed by cyclocondensation with guanidine to afford the pyrimidine derivative 13 , condensation with active methylenes followed by azo coupling of the products followed by cyclization to afford the pyridazines 17a , 17b . The pyridazinone 17b was explored for the synthesis of some novel pyridazine‐fused heterocyclic compounds 19 , 21 , 24a , 24b , 24c , and 26 . All structures were proved via their elemental analyses and spectral data.     

Design,Synthesis, and Bioactivity Evaluation of Novel 3‐(Substituted Phenoxy)‐6‐Methyl‐4‐(3‐Trifluoromethylphenyl) Pyridazine Derivatives

Using 3‐(4‐cyano phenoxy)‐6‐methyl‐4‐(3‐trifluoromethylphenyl) pyridazine (compound A ) as a leading compound, a total of 24 novel 3‐(substituted phenoxy)‐6‐methyl‐4‐(3‐trifluoromethylphenyl) pyridazine derivatives containing two electron‐withdrawing groups on the benzene ring (acylamine and oxime ether) were synthesized. Their herbicidal, insecticidal activities were bioassayed, and the herbicidal activity of compound CD-2 against Brassica campestris was 97.6% at 300 g/ha, which was better than the commercial herbicide diflufenican at the this concentration and is equal to the activity of the leading compound A . Compound CD-4 , CD-5 , CJ-3 , and CJ-5 displayed excellent insecticidal activity against Aphis laburni Kaltenbach (>95%). The results show that the oxime ether substitutions exhibit better bleaching and herbicidal activity than the acylamine ones. The bleaching and herbicidal activity of para‐position substitutions is better than the meta‐position ones. It seems that the para‐position on the benzene ring of oxime ether pyridazine derivatives is one of the key active sites that affect their herbicidal activities.     

Synthesis of nitrogen‐containing heterocycles 10. Reaction of 2‐amino‐1h‐imidazole derivatives with ethoxymethylene compounds

The direct annelation reaction of 4‐substituted 2‐amino‐l‐benzylideneamino‐1H‐imidazoles ( 1 ) or 2‐amino‐1‐isopropylideneamino‐1H‐imidazole ( 8 ) with ethoxymethylenemalononitrile ( I ) gave successfully bicyclic imidazo[1,2‐a]pyrimidine compounds 2 and 9 in high yields. The reactions of other ethoxymethylene compounds of lower reactivity, i.e., ethyl ethoxymethylenecyanoacetate ( II ) and diethyl ethoxymethylenemalonate ( III ), with 2‐amino‐1H‐imidazoles under similar conditions afforded the corresponding enamines 3, 4 and 10 , which, upon heating in the presence of an acid or a base, could readily be cyclized to form imidazopyrimidines except for 1‐isopropylideneamino compound 10 . In general, the 3‐phenyl compounds ( 3b and 4b ) did not cyclize to the type 2 compound resulting in a full recovery of the starting enamines.     

Kinetics and mechanism of gas‐phase pyrolysis of N‐aryl‐3‐oxobutanamide ketoanilides,their 2‐arylhydrazono derivatives,and related compounds

Rates and products of reaction and Arrhenius activation parameters were determined for the gas‐phase thermolysis of 14 substrates of the title compounds using sealed pyrex reactor tubes and HPLC/UV‐VIS to monitor substrate pyrolysis. The 14 compounds under study are N‐phenyl‐3‐oxo‐ ( 1 ), N‐(p‐chlorophenyl)‐3‐oxo‐ ( 2 ), N‐(p‐methylphenyl)‐3‐oxo‐ ( 3 ), and N‐(p‐methoxyphenyl)‐3‐oxobutanamide ( 4 ), in addition to (i) four substrates ( 5–8 ) obtained by the replacement of the pairs of methylene hydrogens at the 2‐position of compounds ( 1–4 ), each pair by a phenylhydrazono group; (ii) three arylhydrazono derivatives ( 9–11 ) in which Cl, CH₃, or OCH₃ groups are substituted at the para position of the phenylhydrazono moiety of compound 5 ; (iii) 3‐oxobutanamide (acetoacetamide, 12 ), N‐phenyl‐3‐oxo‐3‐phenylpropanamide ( 13 ), and N,N′‐diphenylpropanediamide ( 14 ). The reactions were conducted over 374–546 K temperature range, and the values of the Arrhenius log A(s^?1) and E_a(kJ mol^?1) of these reactions were, respectively, 12.0 ± 2.0 and 119.2 ± 17.0 for the ketoanilides ( 1–4, 12–14 ), and 13.0 ± 0.7 and 157.5 ± 8.6 for the arylhyrazono compounds ( 5–11 ). Kinetically, the arylhydrazono derivatives were found to be ca. 1.4 × 10³ to 5.7 × 10³ times less reactive than the parent ketoanilides. A mechanism is proposed to account for reaction products and to rationalize molecular reactivities. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 82–91, 2007     

Pyridazine,oxazine, pyrrole,and pyrrolo[1,2‐a]quinazoline derivatives from malononitrile dimer

2‐Amino‐1,1,3‐tricyano‐3‐bromopropene was obtained from bromination of 2‐amino‐1,1,3‐tricyanopropene (malononitrile dimer) with N‐bromosuccinimide. This bromo derivative reacts with hydrazine hydrate, phenyl hydrazine, and hydroxylamine hydrochloride to afford pyridazine and oxazine derivatives, respectively. In base‐catalyzed reactions with primary aromatic amines and anthranilic acid derivatives, it produces N‐aryl pyrrol‐3,5‐dicarbonitrile and pyrrolo[1,2‐a]quinazolin‐5‐imine, or pyrrolo[1,2‐a]quinazolin‐5‐one derivatives, respectively. The structures of the newly synthesized heterocycles were established on the basis of elemental analyses and spectral data. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:612–616, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10199     

Synthesis of 8‐substituted tetrahydro‐γ‐carbolines

The Fischer reaction is applied to the synthesis of 8‐substituted tetrahydro‐γ‐carbolines with electron‐donating or electron‐withdrawing groups, using catalytic or thermal methods. The reaction conditions must be varied according to the nature of the N 1 substituent of the piperidone. The best results are observed when a releasing group is present on the arylhydrazine and a benzyl substituent on the nitrogen of piperidone. Formation of carbolines with a withdrawing substituent is observed in soft acidic conditions; in others, reaction ended at the hydrazone level or did not evolve.     

1,2,3‐Triazole derivatives of 3‐ferrocenylidene‐2‐oxindole: Synthesis,characterization, electrochemical and antimicrobial evaluation

A series of bioactive, triazole‐linked benzyl, aryl, sugar and aliphatic conjugates of 3‐ferrocenylidene‐oxindole have been synthesized. A facile 1,3‐dipolar‐Huisgen coupling reaction of the respective azides with the 3‐ferrocenylidene‐oxindole N‐propargyl moiety ( 3 ) gave the corresponding conjugates ( 5a–n ). All the newly synthesized compounds ( 5a–n ) were characterized by ¹H‐NMR, ¹³C‐NMR, HRMS, Fourier transform‐infrared spectroscopy and elemental analysis. The UV–Vis and electrochemical studies of these compounds were performed in dimethylsulfoxide solutions. The structure of compound ( 3 ) was determined by single crystal X‐ray diffraction study. These compounds exhibited moderate to good antimicrobial activity against Gram‐positive and Gram‐negative strains.     

Synthesis of 3‐alkylcarbonyloxymethyl derivatives of 5‐fluorouracil

3‐Alkylcarbonyloxymethyl derivatives of 5‐fluorouracil have been synthesized starting with 1‐ethyloxy‐carbonyl‐5‐fluorouracil. Alkylation of the starting material with alkylcarbonyloxymethyl iodides, generated from the corresponding chlorides by the Finkelstein reaction, in the presence of 1,8‐bis(dimethyl‐amino)naphthalene followed by deprotection with 1,1‐dimethylethylamine gave good yields (50‐60%) of the target derivatives after column chromatography. A 90% yield of 3‐acetyloxymethyl‐5‐fluorouracil was obtained when the corresponding commercially available bromide was used, instead of the in situ generated iodide, and the product could be isolated from the crude reaction by crystallization. An alternate path of sequential alkylation of 5‐fluorouracil with alkylcarbonyloxymethyl chlorides in the presence of tertiary amines, exhibiting different reactivities towards the chlorides, gave an excellent yield of 1‐acetyloxymethyl‐3‐propionyloxymethyl‐5‐fluorouracil in the one instance it was attempted, but subsequent deprotection of the 1‐position with methylamine gave only a 24% yield of 3‐propionyloxymethyl‐5‐fluorouracil.     

Synthesis of 3‐Carboxylic derivatives of 1,5‐benzodiazepines

A series of 3‐carboxylic derivatives of disubstituted 1,5‐benzodiazepines (5–9) was synthesized by hetero‐cyclisation from 1,2‐diaminobenzene (1) with dibenzoylmethane (2) followed by bromination on position 3 and by introduction of the carboxylic group or introduction of the malonic moiety. Reduction of the hetero‐cycle gave the perhydro derivative diethyl (2,4‐diphenyl‐1,2,4,5‐tetrahydro‐3H‐1,5‐benzodiazepin‐3‐yl)malonate (9) .     

Synthesis of quinolin‐4‐yl substituted malonates,cyanoacetates, acetoacetates and related compounds

4‐Chloro‐ or 4‐tosyloxyquinolines 1 and 10 react with CH‐acidic compounds such as malonates 2a,b , ethyl cyanoacetate ( 2c ), malononitrile ( 2d ), ethyl acetoacetate ( 2e ), acetylacetone ( 2f ) or dimedone ( 2g ) under mild conditions and good yields to quinolin‐4‐yl substituted derivatives 3‐8 and 11 . With 3‐phenylsulfonylquinolones 1i‐k a redox reaction to 2‐hydroxy‐2‐quinolin‐4‐yl‐malonates 9 was observed. Amination of 3‐nitroquinolinyl malonate 3f leads to malonester‐amides 13 and 14 .     

Oxazoline chemistry part III. Synthesis and characterisation of [2‐(2′‐anilinyl)‐2‐oxazolines] and some related compounds

The syntheses and characterisation of a series of chiral and achiral 2‐(aminophenyl)‐2‐oxazolines and some related compounds is reported. All of the derivatives have been produced by a one‐step procedure involving the treatment of isatoic anhydride (i.e. [2H]‐3, 1‐benzoxazine‐[1H‐2,4‐dione: 1 ) or its 5‐chloro analogue with a slight excess of appropriate amino‐alcohols. In most cases, anhydrous ZnCl₂ is shown to be an effective Lewis acid catalyst for this reaction at reflux temperature in high boiling aromatic solvents (PhCl or PhMe). Oxazolines have been readily formed using rac‐2‐amino‐1‐butanol, (S)‐phenylglycinol, 2‐methyl‐2‐amino‐1‐propanol and (1S,2R) or (IR,2S)‐cis‐ 1 ‐amino‐2‐indanol; yields range from 85% to 22%. The use of aminoalcohols such as 2‐ethanolamine, (±)‐2‐amino‐1‐phenyl‐1‐propanol or 3‐amino‐1‐propanol (to give the corresponding 4,5‐dihydro‐1,3‐oxazine) results in poor yields. The use of other Lewis acid catalysts (silicic acid, Cd(acac)₂·2H₂O, CuCl₂·2H₂O, InCl₃) or higher temperatures did not improve the yields with these latter two substrates. Benzoxazoles and N‐substituted benzoxazoles can also be obtained in reasonable yields from 1 using 2‐aminophenol (36%) or 2‐amino‐3‐hydroxypyridine (45%).     

Synthesis of sulfur‐containing heterocycles: spiropyrimidinetriones,thioxopyrimidinediones, pyrazolidinediones,and isoxazolidinediones—part ii

1‐Aroyl‐2‐styrylsulfonylethene is the precursor for 4,4‐dimethoxycarbonyl‐2′,5‐diaryl‐3‐(1′,3′‐dioxolano)‐1‐thia‐1,1‐dioxide ( 4 ), which is the key intermediate for the synthesis of 7‐aroyl‐11‐aryl‐2,4‐diazaspiro[5,5]undecane‐1,3,5‐trione‐9‐thia‐9,9‐dioxide( 10 )/3‐thioxo‐1,5‐dione‐9‐thia‐9,9‐dioxide ( 11 ), 6‐aroyl‐10‐aryl‐2,3‐diazaspiro[4,5]decane‐1,4‐dione‐8‐thia‐8,8‐dioxide ( 12 )/2‐oxo‐3‐azaspiro [4,5]decane‐1,4‐dione‐8‐thia‐8,8‐dioxide ( 13 ). The new compounds were characterized by IR and ¹H NMR spectral data. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:131–135, 2001     

New syntheses and spectral properties of pteridine‐related heterocycles from 2,5‐diamino‐3,6‐dicyanopyrazine

The reaction of 2,5‐diamino‐3,6‐dicyanopyrazine ( 1 ) as a new pyrazine raw material with alkyl isocyanate in the presence of sodium hydride gave novel heptahydroirnidazo[4,5‐g]pteridine‐2,6,8‐trione ( 2 ), but with tertiary butyl isocyanate gave trihydroimidazo[4,5‐b]pyrazine‐2‐ones ( 3 ). Similar reaction of 1 with alkyl thioisocyanate followed by alkyl iodide gave tetrahydropyrimido[4,5‐g]pteridines ( 4 ). The reac tion of 1 with alkylamine gave the amine‐adduct of the cyano groups which was further reacted with arylaldehyde to give the pyrimido[4,5‐g]pteridine ( 10 ). The products prepared are all of interest as potential pesticides and fluorescent chromophores.     

Synthesis and pharmacological properties of N‐substituted‐N′‐(4,6‐dimethylpyrimidin‐2‐yl)‐thiourea derivatives and related fused heterocyclic compounds

A series of new N‐Substituted‐N′‐(4,6‐dimethylpyrimidin‐2‐yl)‐thiourea derivatives ( 3a , 3b , 3c , 3d ) and related fused heterocyclic compounds ( 4a , 4b , 4c , 4d ) were synthesized using tetrabutylammonium bromide as phase transfer catalyst (PTC). N‐[(2E)‐5,7‐dimethyl‐2H‐[1,2,4] thiadiazolo [2,3‐a] pyrimidin‐2‐ylidene] derivatives ( 4a , 4b , 4c , 4d ) were prepared by oxidative cyclization of 3a , 3b , 3c , 3d . The structures of these novel compounds were characterized by IR, ¹H NMR, ¹³C NMR, mass spectrometry, and the elemental analysis. The crystal structures were determined from single crystal X‐ray diffraction data. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed higher activity against fungi than bacteria. Compounds 3d and 3a exhibited the greatest antimicrobial activity. J. Heterocyclic Chem., 2011.     

Synthesis,lipophilicity and structure of 2,5‐disubstituted 1, 3, 5‐dithiazine derivatives

A series of 2,5‐disubstituted 1,3,5‐dithiazine derivatives were synthesized as potential analogues of the potent dopamine uptake inhibitor GBR 12909. The lipophilic character of the 1,3,5‐dithiazine derivatives were experimentally (log P) and computationally (clog P) determined. The in vitro binding affinities of the 2,5‐disubstituted 1,3,5‐dithiazine derivatives at the dopamine transporter were determined to be much less potent than the binding affinity of GBR 12909 due to steric and electronic effects inherent to the 1,3,5‐dithiazine ring system. The X‐ray crystal structure of 2‐(2‐[bis(4‐fluorophenyl)methoxy]ethyl)‐5‐(3‐phenylpropyl)‐1,3,5‐dithiazine (7) revealed that the 5‐(3‐phenylpropyl) group is in a pseudo‐axial orientation and syn to the 2‐ethoxybenzhydryl moiety.     

Facile Synthesis of 3‐Amino‐2,5‐dihydropyridazines and 4‐Deazatoxoflavin Analogues via [3 + 3] Atom Combination: Approaches to Pyridazine Incorporating Pyrazole Moiety

Arylhydrazones are prepared and reacted with pyrazolylmethylene malononitrile derivatives yielding 2,5‐dihydropyridazines substituted at C‐5 by pyrazole derivatives. Utilizing azaenamine containing a cyano group at the ortho position enabled the formation of the condensed pyridazino[1,6‐a ]quinazoline derivatives. A subsequent acetylation of the synthesized pyridazines led to the formation of pyrimido[4,5‐c ]pyridazine compounds which can be considered as 4‐deazatoxoflavin derivatives. All the new compounds were full‐characterized by the different spectral tools and the unambiguous structural elucidation of 2,5‐dihydropyridazines was done using 2D‐HMBC spectroscopy     

Synthesis of 3‐imidazolylazole derivatives from a new nitrile oxide

The synthesis of a series of 3‐Imidazolylazole derivatives using cycloaddition reactions of a useful new nitrile oxide is described.