Synthesis of Newly Substituted Pyrazoles and Substituted Pyrazolo[3,4‐b]Pyridines Based on 5‐Amino‐3‐Methyl‐1‐Phenylpyrazole

The reaction of the aminopyrazole 1 with benzenesulfonyl chloride, arenediazonium salt, chloroacetyl chloride, ethoxy methyleneamlononitrile and with ethyl 2‐cyano‐3‐ethoxyacrylate gave the substituted 3‐methyl‐1‐phenylpyrazole 2–5a,b . Compound 5b was cyclized to 6 and to 7 by treating it with AlCl₃ and with POCl₃, respectively. Compound 6 converted to 7 by boiling it in POCl₃/PCl₅. Compound 10b was produced through reaction of 9 with acetophenone. Reaction of 1 with benzylidinemalononitrile afforded 11 . New methods for preparation of 15 and 16 are described. The reaction of 8 with malononitrile, thiosemicarbazide, phenyl hydrazine and acetophenone afforded compounds 18–21 . The reaction of 21 with malononitrile gave 22 . Compounds 23–26 were produced upon reaction of 10a with malononitrile, phenyl hydrazine, thiosemicarbazide, semicarbazide and with benzaldehyde, respectively.     

Straightforward Synthesis and Properties of Highly Fluorescent [5]‐ and [7]‐Helical Dispiroindeno[2,1‐c]fluorenes

This work presents a general approach for synthesis of substituted [5]‐helical dispiroindeno[2,1‐c]fluorenes based on Rh‐catalyzed intramolecular cyclotrimerization of triynes. This approach was further extended for the first synthesis of configurationally stable [7]‐helical dispiroindeno[2,1‐c]fluorenes. A series of variously substituted derivatives was prepared and their photophysical and electrochemical properties were evaluated. Their fluorescence emission maxima were in the region of 351–428 nm and quantum yields up to 88 % are the highest measured among the full‐carbon helical compounds.     

A Novel,Simple and Efficient Synthesis of 3‐Amino‐Benzo[d]imidazo[2,1‐b]Thiazole Derivatives via a Multicomponent Procedure

3‐Amino‐benzo[d]imidazo[2,1‐b]thiazoles were synthesized in moderate to good yields in the presence of NH₄Cl via a one pot procedure. All the products were characterized by ¹H NMR, IR, HRMS.     

Structural Transformation of Methoxy‐Substituted Benzo[de]benzo[4,5]imidazo[2,1‐a]isoquinolin‐7‐ones

Structural transformation of two methoxy derivatives of benzo[de]benzo[4,5]imidazo[2,1‐a]‐isoquinolin‐7‐one were determined via spectroscopic analysis. The transformation mechanism was proposed as the breakage and reformation of the lactam bond.     

Synthesis of Substituted Pyrrolo[3,4‐a]carbazoles

The cycloaddition between N‐protected 3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1H‐indoles and substituted maleimides (= 1H‐pyrrole‐2,5‐diones) yielded substituted pyrrolo[3,4‐a]carbazole derivatives bearing an additional succinimide (= pyrrolidine‐2,5‐dione) moiety either at C(5a) or C(10b) depending on the type of the protection group at the indole N‐atom. Derivatives substituted at C(10b) were isolated when the protection group, Me₃Si or Boc (^tBuOCO), was eliminated during the reaction (Schemes 2 and 3), whereas a substitution at C(5a) was observed when an electron‐withdrawing group, Tos (4‐MeC₆H₄SO₂) or pivaloyl (Me₃CCO), was not eliminated (Scheme 1). Complex results were found in reactions between 1‐(trimethylsilyl)‐3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1H‐indole, in contrast to formerly reported results (Scheme 3). Some derivatives of 1H,5H‐[1,2,4]triazolo[1′,2 : 1,2]pyridazino[3,4‐b]indole‐1,3(2H)‐dione were obtained from reactions with 4‐phenyl‐3H‐1,2,4‐triazole‐3,5(4H)‐dione (Scheme 2). All structures were established by spectroscopic data, by calculations, and one representative structure was confirmed by an X‐ray crystallographic analysis (Fig.). Finally, the formation of the different structure types was discussed, and compared with similar reactions reported in the literature.     

Novel Synthesis of 3‐Amino‐4‐oxo‐(2H)‐pyrazolo[3′,4′:4,5]pyrimido‐[2,1‐b]benzothiazole and its 2‐ and 3‐Substituted Derivatives

Reaction of 4H‐pyrimido[2,1‐b]benzothiazole‐2‐thiomethyl‐3‐cyano‐4‐one (1) with hydrazine hydrate/aryl hydrazine/heteryl hydrazine in the presence of anhydrous potassium carbonate and dimethyl formamide afforded 3‐amino‐4‐oxo‐(2H)/aryl/heteryl pyrazolo[3′,4′:4,5]pyrimido[2,1‐b]benzothiazoles in good yield. These pyrazole derivatives on diazotization followed by replacement with hydroxy, chloro, bromo, iodo and on reduction gave the corresponding 3‐substituted derivatives.     

Synthesis of new functionalized imidazo[2,1‐b]thiazoles and thiazolo[3,2‐a]pyrimidines

5‐Oxo‐5H‐[1,3]thiazolo[3,2‐a]pyrimidine‐6‐carboxylic acid ( 4 ), and 6‐methylimidazo[2,1‐b]thiazole‐5‐carboxylic acid ( 17 ) were reacted with amines 6a‐i by the reaction with oxalyl chloride and N, N‐di methyl‐formamide as a catalyst into primary and secondary amide derivatives 7‐14 and 19‐22. From compound 24 N,N'‐disubstituted ureas 26, 27 and perhydroimidazo[1,5‐c]thiazole 29 derivatives of imidazo[2,1‐b]thiazole were prepared. By nmr analysis of compound 29 , the existence of two stereoisomers resulting from both optical, due to centre of chirality at C7′a, and conformational isomerism, due to restricted C5? N6′ bond rotation were proved.     

Synthesis of Isoindolo[2,1‐a]quinazoline‐5,11‐dione Derivatives via the Reductive One‐Pot Reaction of N‐Substituted 2‐Nitrobenzamides and 2‐Formylbenzoic Acids

Various isoindolo[2,1‐a]quinazoline‐5,11‐dione derivatives 3 were synthesized in good yields by means of the reductive reaction of N‐substituted 2‐nitrobenzamides 1 and 2‐formylbenzoic acids 2 in the presence of SnCl₂?2 H₂O under reflux in EtOH (Scheme, Table). The procedure needed two steps, the reduction of the nitro group of the 2‐nitrobenzamide and ring closure by nucleophilic addition of the NH₂ group to both the formyl and carboxylic acid C?O groups.     

Synthesis and Reactivity in [3+2] Cycloadditions of Isoxanthopterin N(5)‐Oxides – A New Synthesis of 6‐Substituted Pteridinediones

Intramolecular condensation of the N‐(4‐amino‐5‐nitrosopyrimidin‐4‐yl)‐2‐chloroacetamide 2 led to the pteridinone N(5)‐oxide 4 , while treatment of 2 with Me₃P yielded the 8‐(chloromethyl)purine 3 . A high‐yielding [3+2] dipolar cycloaddition of the N(5)‐oxide 4 to electron‐poor dipolarophiles, followed by spontaneous N,O‐bond cleavage, gave the C(6)‐substituted pteridinones 8a – 8d that were deprotected to provide the pteridine‐4,7(3H,8H)‐diones 9a – 9d , constituting a new synthesis of pterinones possessing a functionalised side chain at C(6).     

Formal [4+1] Cycloaddition of o‐Aminobenzyl Chlorides with Isocyanides: Synthesis of 2‐Amino‐3‐Substituted Indoles

Reaction of substituted o‐aminobenzyl chlorides with isocyanides in the presence of a weak base (NaHCO₃) at room temperature afforded the diversely functionalized 2‐aminoindoles in good to excellent yields. A formal [4+1] cycloaddition of the in situ generated aza‐ortho‐xylylenes with isocyanides accounted for the reaction outcome.     

Synthesis of novel benzo[h] [1,6]naphthyridines via a rearrangement of hexahydro‐5H‐pyrrolo [2,1 ‐c] [1,4]benzodiazepines

Heating of hexahydro‐5H‐pyrrolo[2,1‐c][1,4]benzodiazepine‐2,5,11‐trione in boiling phosphoryl chloride led to a rearranged product like 3,5‐dichlorobenzo[h][1,6]naphthyridine. This structure was established from X‐ray diffraction analysis.     

A Facile Synthesis of 2‐Substituted 2,3‐Dihydro‐4(1H)‐Azuleno[2,1‐d]Pyrimidinones

A facile, efficient, and novel approach to access 2‐substituted 2,3‐dihydro‐4(1H)‐azuleno[2,1‐d]pyrimidinones was developed by condensation of 2‐amino‐1‐carbamoyl‐3‐phenylazulene with ary1 aldehydes or ketones in ionic liquids by catalyzed p‐toluenesulfonic acid.     

Synthesis of Substituted Pyrazolo[3,4‐b]Pyridines

The synthesis of different substituted pyrazolo[3,4‐b]pyridines by the reaction of 3‐amino‐5‐chloro‐1‐phenylpyrazole‐4‐carboxaldehyde 1 as starting material with some active methylene reagents has been reported.     

Synthesis of Some Novel Arylazo Disperse Dyes Derived from 5‐Amino‐tetrazolo[1,5‐a]pyrimidin‐7‐ol as Coupling Component and Investigation of Their Absorption Spectra

5‐amino‐tetrazolo[1,5‐a]pyrimidin‐7‐ol ( I ) was synthesized by reaction of 5‐amino‐tetrazole with ethyl cyanoacetate in excellent yield. A series of novel 5‐amino‐6‐arylazotetrazolo[1,5‐a]pyrimidin‐7‐ol dyes were prepared by linking o‐, m‐, p‐anisidine, o‐, m‐, p‐chloroaniline, o‐, m‐, p‐nitroaniline, o‐, m‐, p‐toluidine and aniline to 5‐amino‐tetrazolo[1,5‐a]pyrimidin‐7‐ol ( I ). The structure of these dyes were confirmed by UV‐vis, FTIR and ¹H NMR spectroscopic techniques and elemental analysis. The effect of varying pH and solvent upon the absorption ability of 5‐amino‐6‐arylazotetrazolo[1,5‐a]pyrimidin‐7‐ol sudstituted with electron‐withdrawing and electron‐donating groups at their o‐, m‐, p‐position was examined.     

A New Route for the Synthesis of 6‐Substituted [1,2,4]Triazolo[4,3‐a]pyrimidines

A new method of generating the fused heterocyclic system with bridgehead nitrogen, triazolo[4,3‐a]pyrimidine, from 3‐amino‐1,2,4‐triazole and unsaturated halo acids has been described.     

Synthesis of Benzo[α] phenoxazin—5—one Derivatives and Their Interactions with DNA

The spectroscopic properties of benzo[a] phenoxazin-5-one derivatives(3a-3m)including newly synthesized 3k-3m from 4-nitrosoaniline hydrochlorides and ethyl 1,3-dihydroxy-2-naphthoate were studied.Compound 31 was converted into a covalent product with DNA,which had a blue shift of the fluorescence maximum,Compounds 3a-3k were fornd to undergo interation with DNA and their complexes with DNA had a red shift of the fluorescence maximum and showed increasing melting temperature of DNA,compound 3m-DNA had a blue shift of the fluorescence maximum to 3m and showed decreasing melting temperature of DNA.