Regiospecific synthesis of 5‐(1H‐indol‐2‐yl)‐1‐ and 2‐methyl‐6,7‐dihydro‐2H‐indazole isomers

A regiospecific approach to each N‐methyl‐5‐(1H‐indol‐2‐yl)‐6,7‐dihydro‐2H‐indazole isomer is reported. The 1‐methyl isomer 1 was prepared from 5‐bromo‐1‐methyl‐6,7‐dihydro‐1H‐indazole 3 and indole‐2‐boronate 5 by palladium catalyzed Suzuki coupling. The 2‐methyl regioisomer 2 was synthesized via addition of lithium (1‐carboxylato‐1H‐indole‐2‐yl)lithium 6 with 2‐methyl‐2,4,6,7‐tetrahydro‐indazol‐5‐one 8 followed by acid catalyzed dehydration.     

Synthesis and reactions of n‐methyl‐4‐(methylthio)thieno[2,3‐d]‐pyrimidinium salts

Two methods for the preparation of N‐methyl‐4‐(methylthio)thieno[2,3‐d]pyrimidinium salts 6a,b and 13a,b are described. Treatment of 6a,b and/or 13a,b with active methylene compounds such as malononitrile and ethyl cyanoacetate in the presence of sodium methoxide caused nucleophilic addition followed by elimination of methanethiol, giving the corresponding N‐methyl‐4‐ylidenethieno[2,3‐d]‐pyrimidines 7a,b, 8a,b, 14a,b and 15a,b .     

Synthetic and spectroscopic studies of some new 2‐[1‐aryl‐4{4‐methoxyphenyl}‐6‐thioxo‐1,6‐dihydro‐1,3,5‐triazinyl]amino/hydrazonothiazolidin‐4‐ones

A series of 4‐thiazolidinones having triazinethione moieties have been synthesized by the systematic chemical modification of S‐benzylmercapto‐1‐aryl‐4‐(4‐methoxyphenyl)‐1,6‐dihydro‐1,3,5‐triazine‐6‐thione.     

FeCI3‐promoted [3+3] cycloaddition: Efficient preparation of 1,2‐dihydro‐2‐oxo‐3‐pyridinecarboxylate and 1,2‐dihydro‐2‐oxo‐3‐pyridinecarboxamide derivatives

A facile approach was developed on assembly of the 2‐pyridone nucleus by ferric chloride promoted [3+3] cycloaddition in propionic acid. The tandem process involves cyclization of Michael adduct followed by aromatization. Thus, different substituted 1,2‐dihydro‐2‐oxo‐3‐pyridinecarboxylate and 1,2‐dihydro‐2‐oxo‐3‐pyridinecarboxamide derivatives were prepared in good yields from various enones with malonamic ester and malonamide, respectively     

Preparation of 4,5‐dihydro‐1,3‐selenazoles by reaction of aromatic primary selenoamides with acetylenedicarboxylate

Reactions of primary selenoamides with dimethyl acetylenedicarboxylate afforded 2‐aryl‐5‐methoxy‐carbonylmethylene‐4,5‐dihydro‐1,3‐selenazol‐4‐ones in moderate to high yields. Reactions of the primary selenoamides with acetylenedicarboxylic acid gave 2‐aryl‐5‐carboxymethylene‐4‐ethoxy‐4,5‐dihydro‐1,3‐selenazol‐4‐ols in moderate yields.     

1,3‐Dipolar cycloadditions: Investigation of cycloadditions of c‐aryl‐n‐(4‐chlorophenyl) nitrones to n‐cinnamoyl piperidines

Investigation of cycloadditions of C‐aryl‐N‐(4‐chlorophenyl)nitrones to N‐cinnamoyl piperidines was carried out. Two diastereoisomeric and one regioisomeric cycloadducts, and in some cases ring‐opened compounds were characterized by spectroscopic and X‐ray data. Molecular modelling was carried out for conformational studies.     

Convenient way to 5‐substituted 4‐amino‐2,3‐dihydro‐4H‐1,2,4‐triazole‐3‐thiones

Various 4‐amino‐2,3‐dihydro‐4H‐triazoles with aromatic, aliphatic and heterocyclic substituents at the C(5) position were synthesized from corresponding esters and thiocarbohydrazide. This method allows the synthesis these heterocycles in a short time and at reduced expenses.     

Green multicomponent synthesis of 1,2‐dihydro‐pyrimido[1,2‐a]‐benzimidazole‐3‐carbonitrile

1,2‐dihydro‐pyrimido[1,2‐a]benzimidazole‐3‐carbonitrile derivatives were synthesized via the three‐component reaction of aldehyde, malonodinitrile and 2‐aminobenzimidazole in water under microwave irradiation. The new protocol has the advantages of excellent yield, low cost, reduced environment impact, wide scope and convenient procedure.     

Chemo,stereo, and regioselective addition of α‐(2‐methoxyaryl)‐N‐aryl nitrones to diarylidineacetone: Synthesis of novel isoxazolidines

A new set of 2,3,4,5‐tetrasubstituted isoxazolidines with an α,β‐unsaturated carbonyl function at position 4 has been synthesized. The multicomponent approach and microwave irradiation protocol have also been investigated for the above synthesis.     

Synthesis of novel 3,5,7‐triaryl‐5,6‐dihydro‐4h‐1,2,5‐triazepines

Several hitherto unknown 3,5,7‐triaryl‐5,6‐dihydro‐4H‐1,2,5‐triazepines have been synthesised by cyclocondensation of N,N‐bis(phenacyl)anilines with hydrazine hydrate in ethanol or ethyleneglycol under reflux condition. Increased yields were obtained in the presence of p‐toluenesulfonic acid compared to the uncatalysed reaction.     

Facile synthesis of 6‐aryl‐5H‐8‐oxa‐4b, 7‐diaza‐benzo[a]azulen‐9‐one derivatives,new tricyclic heterocycles

8‐Oxa‐4b,7‐diaza‐benzo[a]azulene‐9‐one system, a new tricyclic heterocyclic framework is designed through a simple and convenient synthetic sequence. Its 6‐aryl derivatives are synthesized starting from ethyl indole‐2‐carboxylate. Reaction of differently substituted phenacyl bromides with ethyl indole‐2‐carboxylate, treatment of the resultant N‐substituted indole‐2‐carboxylates with hydroxylamine hydrochloride to provide corresponding oximes, subsequent ester hydrolysis followed by dehydrative cyclisation furnished the desired compounds 5 a‐g .     

Fused pyridines by a tandem aza‐wittig / heterocyclization strategy: Synthesis of 1,2,4‐triazolo[1,5‐a]pyridines and pyrido[1,2‐b][1,2,4]triazines

The iminophosphorane 1‐amino‐6‐(triphenylphosphoranylideneamino)‐2‐oxo‐4‐phenyl‐1,2‐dihydro‐pyridine‐3,5‐dicarbonitrile 2 prepared from 1,6‐diaminopyridine 1 reacts with heterocumulenes such as carbon disulfide and phenylisocyanate, and with acid chlorides, acid anhydrides and haloketones to give directly the title compounds in an one‐pot aza‐Wittig / heterocyclic‐ring closure process with good yields.     

White Luminescence from Multiple‐Dye‐Doped Electrospun DNA Nanofibers by Fluorescence Resonance Energy Transfer

A DNA spin‐off : Electrospinning of DNA complexes gives nanofibers with a highly ordered morphology that allows homogeneous distribution of encapsulated multiple chromophores. The emission color can be controlled by suitable choice of the donor–acceptor pair and the doping ratio. Pure white‐light emission from nanofibers is demonstrated (see picture).

     

Synthesis of thiazolo[3,2‐d][1,2,4] triazines through palladium‐catalyzed heteroannulation of acetylenic compounds

The reaction of 6‐methyl‐5‐(prop‐2‐ynylthio)‐5,6‐dihydro‐1,2,4‐triazin‐3(4H)‐one 1 with various iodobenzenes 2 in the presence of palladium catalyst leads to the formation of substituted triazolotriazines.     

A novel synthesis of indole derivatives by the reaction of N‐arylhydroxamic acids with malononitrile

An approach to indole derivatives from N‐arylhydroxamic acids and malononitrile via a [3,3]‐sigmatropic rearrangement and intramolecular cyclization is described. Reactions of N‐arylhydroxamic acids 1a‐c, 2a‐c and 3a‐c with malononitrile in the presence of triethylamine at room temperature gave the corresponding α‐cyanoacetamide derivatives 4a‐c, 5a‐c, 6a‐c, 7a‐c and 8a‐c . Thermal treatment of 4a‐c, 5a‐c and 7a‐c with a base, e.g. triethylamine and sodium methoxide, caused intramolecular cyclization and deacylation to afford the corresponding indole derivatives 9‐11 .     

Synthesis of 1,3‐thiazole and 1,2,4‐oxadiazole substituted spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones

Some new derivatives of spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐dione with the heterocyclic ring such as substituted thiazole and 1,2,4‐oxadiazole attached to the indolinone ring via CH₂ linkage has been synthesized in moderate yields. The synthesis have been carried out by making use of the reactivity of the NH group of the indolinone moiety present in spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐dione.     

A convenient synthesis and biological activities of novel 6‐aryl‐3‐(1,2,3,4‐tetrahydroxybutan‐1‐yl)‐7H‐1,2,4‐triazolo‐[3,4‐b][1,3,4]thiadiazines

A series of novel 6‐aryl‐3‐(1,2,3,4‐tetrahydroxybutanol‐1‐yl)‐7H‐1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazines were easily synthesized in high yields by means of the reactions of 4‐amino‐5‐(1,2,3,4‐tetrahydroxybutyl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione ( 1 ) with substituted ω‐bromoacetophenones or ω‐chloroacetophenone. Nearly all of the title compounds possess plant growth‐promoting activities.     

Synthesis of some novel 2,6‐disubstituted pyridazin‐3‐ones as TMC120 analogues

Different analogues of TMC120 derived from pyridazin‐3(2H)‐one rings were synthesized by coupling of 3,6‐dichloropyridazine with arylacetonitriles, phenols and/or aniline derivative followed by hydrolysis and alkylation with different benzyl bromide derivatives.     

Microwave‐promoted oxidation of 1,3,5‐trisubstituted 4,5‐dihydro‐1H‐pyrazoles by in‐situ generation of NO+ and NO respectively from sodium nitrite and sodium nitrate in acetic acid

Microwave‐assisted aromatization of 1,3,5‐trisubstituted 4,5‐dihydro‐1H‐pyrazoles by in‐situ generation of NO⁺ and NO₂⁺ respectively from sodium nitrite and sodium nitrate in acetic acid has been carried out efficiently under mild reaction conditions in good to excellent yields.