Synthesis of novel 5‐aryl‐1H‐tetrazoles

In this study phenylselenocyanate and some of its derivatives (o‐Cl, p‐Cl, p‐Br, o‐NO₂, p‐NO₂, o‐CH₃, p‐CH₃, o‐COOH, p‐COOH, p‐OCH₃ substituted) were synthesized ( 3a–3j ). The synthesized compounds were converted to 5‐aryl‐1H‐tetrazole ( 4a–4j ), by Et₃N ċ HCl‐NaN₃ in toluene, which are a new series of phenylselanyl‐1H‐tetrazoles. The structure of all the presently synthesized compounds were confirmed using spectroscopic methods (FTIR, ¹H NMR, MS). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:255–258, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20293     

Synthesis and anti‐inflammatory activity of 8H‐1‐thia‐8‐aza‐dibenzo[e,h]azulenes

Synthesis of a novel class of fused heterotetracyclic compounds, 8H‐1‐thia‐8‐aza‐dibenzo[e,h]azulenes ( VII ), is described. Starting N‐benzoyl‐protected 5H‐dibenzo[b,f]azepine ( XI , PG = Bz) was oxidized to 5‐benzoyl‐10,11‐epoxy‐10,11‐dihydro‐5H‐dibenzo[b,f]azepine ( 2 ), which subsequently rearranged in Lewis acid‐induced epoxide ring opening to give 5‐benzoyl‐5,11‐dihydro‐10H‐dibenzo[b,f]azepin‐10‐one ( 3 ). Vilsmeier reaction of 3 provided β‐chlorovinyl aldehyde 4 that readily cyclized with ethyl 2‐mercaptoacetate to form dibenzazepino[4,5]‐fused thiophene structure 5 . Further transformation of substituent at C‐2 position of 5 and N‐deprotection led to final aminoalkoxy derivatives 9 . All compounds with tetracyclic skeleton were tested in vitro for their anti‐inflammatory activity. J. Heterocyclic Chem., (2011).     

Phosphorus heterocycles from 2‐(2‐hydroxyphenyl)‐1H‐benzimidazole

Sixteen different P(III) and P(V) heterocycles derived from 2‐(2‐hydroxyphenyl)‐1H‐benzimidazole ( 1 ) are reported. In these heterocycles the phosphorus atom is part of a six‐membered unsaturated ring. They were mainly studied by multinuclear NMR. The X‐ray diffraction of 3,4‐ benzimidazole‐5,6‐benzo‐2‐dimethylamino‐2‐seleno‐ 1,3,2‐oxazaphosphorinane is reported. Phosphoranes derived from 1 and 3,5‐di‐tert‐butylcatechol, and bearing Cl, NMe₂, or phenyl as substituent at phosphorus are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:307–320, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20021     

Synthesis of pinacol esters of 1‐alkyl‐1H‐pyrazol‐5‐yl‐ and 1‐alkyl‐1H‐pyrazol‐4‐ylboronic acids

Starting from 1H‐pyrazol, a wide number of 1‐alkyl‐1H‐pyrazol‐4‐yl and 1‐alkyl‐1H‐pyrazol‐5‐ylboronic acids and their pinacol esters were synthesized and characterized. The key step in the described methodology is the regioselective lithiation of the pyrazole ring. The synthesized pinacolates are stable under prolonged storage and can be used as convenient reagents in organic synthesis.     

A Simple Synthesis of 5‐(2‐Aminophenyl)‐1H‐pyrazoles

A four‐step synthesis of 1‐substituted 5‐(2‐aminophenyl)‐1H‐pyrazoles 5 as a novel type of histamine analogs and versatile building blocks for further transformations was developed. The synthesis starts from commercially available 2‐nitroacetophenone ( 12 ), which is converted into the enamino ketone 13 as the key intermediate. Cyclization of the key intermediate 13 with monosubstituted hydrazines 14a – 14l afforded the 5‐(2‐nitrophenyl)‐1H‐pyrazoles 17a – 17l . Finally, catalytic hydrogenation of the nitro compounds 17a, 17c – 17e , and 17g – 17j furnished the title compounds 5a, 5c – 5e , and 5g – 5j , respectively, in good yields. As demonstrated by some further transformations, additional functionalization of compounds 17 and 5 is feasible, either by electrophilic substitution at C(4) of the pyrazole ring, or at the NH₂ group.     

Synthesis of Some New Spiro,Isolated and Fused Heterocycles Based on 1H‐indole‐2‐One

The reaction of 3‐benzoylcyanomethylidine‐1(H)‐indole‐2‐one ( 1 ) with a variety of active methylene compounds, thioglycolic acid, glycine, hydrazine hydrate and phenyl hydrazine led to the formation of compounds 4a‐d‐10 . 3‐Thiosemicarbazide‐1(H)‐indole‐2‐one 2 on reaction with α‐halocarbonyl compounds gave compounds 11a‐c, 12a‐c . The latter compounds on heating with phosphoryl chloride, cyclization takes place via losing water to give the angular tetracyclic compounds 13a,b and 14a‐c . Cyanoacetic hydrazone derivative 3 readily cyclized upon heating in triethyl orthoformate to give the tricyclic system, oxopyridazino indole 15 . On the other hand, the reaction of 3 with benzylidine malononitrile and benzylidene ethylcyanoactate gave the pyranyl hydrazone derivatives 16a,b .     

Synthesis and biological evaluation of 9‐thia‐5,10‐dideazafolic acid

The folate analogue, 9‐thia‐5,10‐dideazafolic acid ( 3b ), was obtained in an efficient two‐step procedure in an overall yield of 60%. The previously unknown intermediate dimethyl‐thiocarbamic acid S‐(2‐amino‐3,4‐dihydo‐4‐oxo‐pyrido[2,3‐d]pyrimidin‐6‐yl) ester ( 5 ) was prepared via the condensation of 2,6‐diamino‐3H‐pyrimidin‐4‐one and S‐(2‐malonaldehyde)‐1,1,3,3‐tetramethylthiouronium bromide ( 4 ). Compound 5 , in a one pot procedure, was deprotected using sodium hydroxide and then coupled to diethyl N‐[(4‐chloromethyl)benzoyl]‐L‐glutamate, followed by saponification of the ethyl esters to give the 9‐thia‐5,10‐dideazafolic acid ( 3b ). Compound 3b was a potent inhibitor of human 5‐aminoimidazole‐4‐carboxamide ribonucleotide transformylase (K_i of 8 ± 5 μM) and showed no inhibition of human glycinamide ribonu‐cleotide transformylase at concentrations as high as 50 μM. Compound 3b was screened by the National Cancer Institute Developmental Therapeutics Program against 60 human tumors and was found to be active against a leukemia RPMI‐8226 cell line where the LC₅₀ was 1 μM.     

Synthesis,Characterization and Explosive Properties of 1,3‐Dimethyl‐5‐amino‐1H‐tetrazolium 5‐Nitrotetrazolate

1,3‐Dimethyl‐5‐amino‐1H‐tetrazolium 5‐nitrotetrazolate ( 5b ) was synthesized in high yield from 1,4‐dimethyl‐5‐amino‐1H‐tetrazolium iodide ( 5a ) and silver 5‐nitrotetrazolate. Both new compounds ( 5a and 5b ) were characterized using vibrational (IR and Raman) and multinuclear NMR spectroscopy (¹H, ¹³C and ¹⁵N), elemental analysis and single‐crystal X‐ray diffraction. 5a crystallizes in an orthorhombic cell: Pbca, a = 11.5016(4), b = 13.7744(5), c = 13.7744(5) Å, V = 1638.2(1) ų, Z = 8, ρ = 1.955 g cm^?3, R₁ = 0.0210 (F > 4σ(F)), wR₂ (all data) = 0.0542; whereas 5b crystallizes in a monoclinic cell: C1c, a = 14.5228(8), b = 5.0347(2), c = 13.7217(7) Å, β = 112.11(1)°, V = 929.6(2) ų, Z = 4, ρ = 1.630 g cm^?3, R₁ = 0.0279 (F > 4σ(F)), wR₂ (all data) = 0.0585. The sensitivity of 5b to classical stimuli was determined by using standard BAM tests and its thermal stability was assessed by DSC measurements. In addition, its heat of combustion was determined by bomb calorimetry measurements. The EXPLO5 was used to calculate the detonation pressure (P) and velocity (D) of 5b (P = 13.3 GPa and D = 6379 m s^?1), as well as those of its mixtures with ammonium nitrate (P = 23.2 GPa and D = 7862 m s^?1) and ammonium dinitramide (P = 29.6 GPa and D = 8594 m s^?1). Compound 5b is a hydrolytically stable solid with a high melting point (160 °C) and thermally stable to 190 °C with a very low sensitivity to friction (>360 N) and impact (>30 J) and good performance in combination with an oxidizer making it of interest in new environmentally friendly, insensitive explosive formulations.     

Zwitterionic 5‐(1‐piperidiniomethyl)‐1H‐tetrazolide

The title compound, C₇H₁₃N₅, a tetrazole analogue of betaines, exists as a zwitterion, with the H atom of the tetrazole ring being transferred to the piperidine ring N atom. The tetrazole ring symmetry is close to C_2v, which suggests strong charge delocalization in the N—C—N fragment of the ring. There are classical hydrogen bonds in the structure which are responsible for the formation of two‐membered aggregates.     

Facile and Regioselective Synthesis of Substituted 1H‐Pyrazolo[3,4‐b]quinolines from 2‐Fluorobenzaldehydes and 1H‐Pyrazol‐5‐amines

The present article concerns the scope and limitations of the regioselective condensation of 2‐fluorobenzaldehydes with 1H‐pyrazol‐5‐amines, leading to the synthesis of substituted 1H‐pyrazolo[3,4‐b ]quinolines ( PQ ), in the presence of a base catalyst (DABCO and 2,4,6‐trimethylpyridine). A method to obtain these nitrogen heterocycles with fluorine or trifluoromethyl substituents in different positions in the carbocyclic ring was developed as a part of a systematic research on the influence of fluorine‐containing substituents on the parameters of PQ . Those compounds, characterized by high‐fluorescence intensity, have been tested as emitters for the organic light‐emitting diodes since 1997. The functionalization of PQ causes changes in various parameters, for example, HOMO and LUMO levels, which are important for the adjustment of fabricated organic light‐emitting diodes. One of the easiest methods of PQ preparation, namely, the condensation of substituted anilines with 5‐chloro‐1H‐pyrazole‐4‐carbaldehydes, is not regioselective. The method described in this study allows synthesizing of 1H‐pyrazolo[3,4‐b ]quinolines with good yields and high selectivity – only the expected isomer is obtained. As various different 2‐fluorobenzaldehydes are commercially available, and 1H‐pyrazol‐5‐amines with different substituents are easy to prepare, the method could be a good alternative to the already known procedures. All possible mechanisms of the reaction were also thoroughly studied.     

Iron Salts in the Catalyzed Synthesis of 5‐Substituted 1H‐Tetrazoles

Clicking iron : Cheap and environmentally friendly [Fe(OAc)₂] is used for the catalysis of cycloadditions between aryl nitriles and trimethylsilyl azide to prepare substituted 1H‐tetrazoles in good yield (see scheme).

     

Synthesis of some new 1‐acyl‐5‐aryl‐3‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐4,5‐dihydro‐1H‐pyrazole

Some new compounds (E)‐3‐aryl‐1‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐prop‐2‐en‐1‐ones 5a–e were prepared by 1‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐ethanone and various aromatic aldehydes. Then one pot reaction was happened by compounds 5a–e with hydrazine hydrate in acetic acid or propionic acid, respectively, to give the title compounds 1acyl‐5‐aryl‐3‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐4,5‐dihydro‐1H‐pyrazoles 6a–i . All structures were established by MS, IR, CHN, ¹H‐NMR and ¹³C‐NMR spectral data. J. Heterocyclic Chem., (2012).     

Selenium‐Containing Heterocycles from Isoselenocyanates: Synthesis of 1H‐5‐Selena‐1,3,6‐triazaaceanthrylene Derivatives

The reaction of aryl isoselenocyanates 8 with methyl 3‐amino‐4‐chloro‐1‐ethylpyrrolo[3,2‐c]quinoline‐2‐carboxylate ( 6 ) in boiling pyridine leads to tetracyclic selenaheterocycles of type 9 in high yield (Scheme 3). A reaction mechanism via an intermediate selenoureido derivative A and cyclization via nucleophilic substitution of Cl by Se is proposed (Schemes 3 and 5). The reaction of 6 with 4‐bromophenyl isothiocyanate yields the analogous thiaheterocycle 12 (Scheme 4). The molecular structures of 9c and 12 have been established by X‐ray crystallography.     

An Efficient Synthesis of New 5‐(1‐Aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles from 1‐Aryl‐1H‐pyrazole‐4‐carbonitriles via [3 + 2] Cycloaddition Reaction

A series of new 5‐(1‐aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles 4a‐l were synthesized via [3 + 2] cycloaddition reaction from 1‐aryl‐1H‐pyrazole‐4‐carbonitriles 3a‐l , sodium azide and ammonium chloride, using dimethylformamide (DMF) as solvent, in good yields: 64–85%. The structures of these newly synthesized compounds were determined from the IR, ¹H‐ and ¹³C‐NMR spectroscopic data and elemental analyses.     

Efficient synthesis of 1‐substituted‐4‐phenyl‐1, 4‐dihydro‐5H‐tetrazole‐5‐thione and (1‐phenyl‐1H‐tetrazol‐5‐yl)thioacetyl derivatives

A new and convenient synthesis of a variety of N‐ and S‐substituted tetrazoles has been developed via azide and Mannich reaction methods. Compounds were characterized by elemental analysis, MALDI MS, and ¹H NMR data. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:637–643, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20353     

Novel Bis(2‐(5‐((5‐phenyl‐1H‐tetrazol‐1‐yl)methyl)‐4H‐1,2,4‐triazol‐3‐yl)phenoxy)Alkanes: Synthesis and Characterization

In this study, 10 different substituted aromatic bis‐benzaldehydes were synthesized by treating hydroxy benzaldehydes with various dihaloalkanes. Bis aldehydes 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j were treated with 2‐(5‐phenyl‐1H‐tetrazole‐1‐yl)acetohydrazide ( 3 ) in acidic medium and in the presence of ammonium acetate to yield a series of new isomeric bis(2‐(5‐((5‐phenyl‐1H‐tetrazol‐1‐yl)methyl)‐4H‐1,2,4‐triazol‐3‐yl)phenoxy)alkanes ( 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j ) in excellent to good yield. The newly synthesized compounds were characterized by the available spectroscopic analysis.     

Nitration Products of 5‐Amino‐1H‐tetrazole and Methyl‐5‐amino‐1H‐tetrazoles – Structures and Properties of Promising Energetic Materials

The nitration of 5‐amino‐1H‐tetrazole ( 1 ), 5‐amino‐1‐methyl‐1H‐tetrazole ( 3 ), and 5‐amino‐2‐methyl‐2H‐tetrazole ( 4 ) with HNO₃ (100%) was undertaken, and the corresponding products 5‐(nitrimino)‐1H‐tetrazole ( 2 ), 1‐methyl‐5‐(nitrimino)‐1H‐tetrazole ( 5 ), and 2‐methyl‐5‐(nitramino)‐2H‐tetrazole ( 6 ) were characterized comprehensively using vibrational (IR and Raman) spectroscopy, multinuclear (¹H, ¹³C, ¹⁴N, and ¹⁵N) NMR spectroscopy, mass spectrometry, and elemental analysis. The molecular structures in the crystalline state were determined by single‐crystal X‐ray diffraction. The thermodynamic properties and thermal behavior were investigated by using differential scanning calorimetry (DSC), and the heats of formation were determined by bomb calorimetric measurements. Compounds 2, 5 , and 6 were all found to be endothermic compounds. The thermal decompositions were investigated by gas‐phase IR spectroscopy as well as DSC experiments. The heats of explosion, the detonation pressures, and velocities were calculated with the software EXPLO5, whereby the calculated values are similar to those of common explosives such as TNT and RDX. In addition, the sensitivities were tested by BAM methods (drophammer and friction) and correlated to the calculated electrostatic potentials. The explosion performance of 5 was investigated by Koenen steel sleeve test, whereby a higher explosion power compared to RDX was reached. Finally, the long‐term stabilities at higher temperatures were tested by thermal safety calorimetry (FlexyTSC). X‐Ray crystallography of monoclinic 2 and 6 , and orthorhombic 5 was performed.     

1‐Acetyl‐3‐ferrocenyl‐5‐methyl‐1H‐pyrazole and 1‐acetyl‐5‐ferrocenyl‐3‐(2‐pyrid­yl)‐1H‐pyrazole

Mol­ecules of 1‐acetyl‐3‐ferrocenyl‐5‐methyl‐1H‐pyrazole, [Fe(C₅H₅)(C₁₁H₁₁N₂O)], form a centrosymmetric dimer generated by a combination of one C—H⋯π(pyrazole) and one C—H⋯π(cyclo­penta­dienyl) inter­action. The dimers are linked by C—H⋯π inter­actions, involving the pyrazole rings as acceptors, into layers parallel to (10). Mol­ecules of 1‐acetyl‐5‐ferrocenyl‐3‐(2‐pyrid­yl)‐1H‐pyrazole, [Fe(C₅H₅)(C₁₅H₁₂N₃O)], are linked by C—H⋯O inter­actions into a chain running in the [010] direction. Two chains of this type passing through each unit cell are connected by O⋯π(pyridyl) inter­actions into an [010] double chain.