Synthesis of a novel class of 3‐(2′‐benzothiazolyl)‐2,3‐dihydroquinazolin‐4(1H)‐ones under solvent‐free and catalyst‐free conditions

A solvent‐ and catalyst‐free one‐pot three‐component condensation reaction approach was developed for the synthesis of a new class of 3‐(2′‐benzothiazolyl)‐2,3‐dihydroquinazolin‐4(1H)‐ones in relatively good yields.     

Diverse reactivity of α‐carbanions derived from alkylidenephosphoranes toward 2‐(1λ5‐diazynylidene)‐1H‐indene‐1,3‐(2H)dione. General approach to conjugated oxadiazines,pyridazines and spiro[3]pyrazoles

Different types of phosphonium carbanions were applied to 2‐diazonio‐1,3‐dioxo‐2,3‐dihydro‐1H‐inden‐2‐ide ( 1 ) in order to synthesize a number of condensed and fused N‐heterocycles. When 1 was treated with cyanomethyltriphenylphosphonium chloride oxadiazine‐, and pyridazine derivatives were obtained whereas bis‐indanylidene derivatives resulted from the reaction of 1 with methyl_ and ethyltriphenylphosphonium bromides. On the other hand, a series of substituted and unsubstituted spiro[3′]pyrazoles were obtained from the di azo substrate when reacted with vinyl_and allyltriphenylphosphonium bromides.     

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.     

Regioselective synthesis of pentacyclic polyheterocycles: Sequential [3,3] sigmatropic rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl‐1,8‐naphthyridin‐2(1H)‐ones

A number of 4‐aryloxymethyl‐6‐phenyl‐2H‐pyrano[3,2‐c][1,8]naphthyridin‐5(6H)‐ones ( 4a‐f ) are regioselectively synthesized in 72‐78% yield by the Claisen rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl‐1,8‐naphthyridin‐2(1H)‐ones ( 3a‐f ) in refluxing chlorobenzene for 4‐6 h. These products are then subjected to a second Claisen rearrangement catalyzed by anhydrous AlCl₃ at room temperature for 2 h to give hitherto unreported pentacyclic heterocycles ( 5a‐f ) in 78‐85% yield.     

Synthesis and biological activity of 3‐[(6‐chloropyridin‐3‐yl)methyl]‐6‐substituted‐6,7‐dihydro‐3H‐1,2,3‐triazolo[4,5‐d]‐pyrimidin‐7‐imines

A series of 3‐[(6‐chloropyridin‐3‐yl)methyl]‐6‐substituted‐6,7‐dihydro‐3H‐1,2,3‐triazolo[4,5‐d]pyrimidin‐7‐imines were designed and synthesized via a multi‐step sequence using 2‐chloro‐5‐(chloromethyl)‐pyridine as the starting material. Various primary aliphatic amines, hydrazine and hydrazide reacted with 3 to obtain the cyclization products 4 . Their structures were confirmed by ¹H NMR and elemental analyses, some of them were also confirmed by IR, ¹³C NMR, MS and single crystal X‐ray diffraction. The preliminary bioassay indicated that some of the target compounds 4 displayed moderate to weak fungicidal activity and insecticidal activity.     

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.     

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     

Electrophilic aromatic substitution of 3‐alkoxy‐6‐alkyl‐2‐cyano‐4,5,6a,11‐tetraazabenzo[a]fluorene with orthoesters

Fused tetracycles, 6‐alkyl‐3‐alkoxy‐2‐cyano‐4,5,6a,11‐tetraazabenzo[a]fluorene derivatives ( 5a , b , c , d , e , f ), are synthesized from 2‐alkoxy‐5‐(benzimidazol‐2‐ylidene)‐3‐cyano‐6‐imino‐5,6‐dihydro‐pyridines ( 4b , c ), and when refluxed in ethyl orthoacetate or ethyl orthopropionate, the elecrophilic aromatic substitution occurs at the ortho position of the cyanopyridine ring in the fused tetracycles ( 5b , c , e , f ) to afford 6‐alkyl‐3‐alkoxy‐2‐cyano‐1‐ethyl‐4,5,6a,11‐tetraazabenzo[a]fluorenes( 6b , c , e , f ).     

A simple and efficient synthesis of novel N,N′‐bis (1H‐pyrrol‐1‐yl)‐1‐[2‐(2‐aryl‐5‐methyl‐3‐oxo‐2,4‐dihydro‐3H‐1,2,4‐triazol‐4‐yl)ethyl]‐1H‐1,2,3‐triazole‐4,5‐dicarboxamides

One‐pot reaction of 3‐aryl‐5‐methyl‐1,3,4‐oxadiazolin‐2‐ones 1a‐g with ethanolamine yielded the 4‐(2‐hydroxyethyl)‐2‐aryl‐5‐methyl‐2,4‐dihydro‐3H‐1,2,4‐triazolin‐3‐ones 2a‐g which were converted to the azido compounds 6a‐g . These azides on 1,3‐dipolar cycloaddition with DMAD afforded the dimethyl‐1‐[2‐(2‐aryl‐5‐methyl‐3‐oxo‐1,2,4‐triazol‐4‐yl)ethyl]‐1H‐1,2,3‐triazol‐4,5‐dicarboxylates 7a‐g which on conversion to bishydrazides 8a‐g and further cyclisation with 2,5‐hexanedione afforded the title compounds 9a‐g . This new short route for the so far unkown bis‐(triazolinone‐triazole)ethanes involves mild and convergent 1,3‐dipolar cycloaddition reaction yielding overall good yields of the products.     

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.     

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.     

Synthesis of α‐diaminomethylenebutyrolactams by the reaction of α‐cyanobutyrolactams with n‐trimethylsilylamines

Successive treatment of α‐cyanobutyrolactams 1 with N‐trimethylsilylamines and water gave the corresponding α‐diaminomethylenebutyrolacatms 2 in good yields. In the NOESY spectra of 2 , the E isomer, the NOE observed between β‐CH₂ (butyrolactam) and N‐CH₂ (morpholine, pyrrolidine) or N‐CH₃ (dimethylamine) indicated a cis configuration of these groups.     

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.     

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.     

Synthesis of some 3‐aryl‐1H‐isochromene‐1‐thiones

A rapid microwave‐accelerated thionation of some 3‐substitued isocoumarins to corresponding 1‐thio‐isocoumarins was achieved employing Lawesson's reagent under solventless conditions.     

Synthesis and herbicidal activity of 2‐(3‐(trifluoromethyl)‐5‐(alkoxy)‐1H‐pyrazol‐1‐yl)‐4‐aryloxypyrimidine derivatives

A series of 2‐(3‐(trifluoromethyl)‐5‐(alkoxy)‐1H‐pyrazol‐1‐yl)‐4‐aryloxypyrimidine derivatives were designed and synthesized. The structures of all the title compounds were confirmed by ¹H NMR and elementary analysis. These compounds were screened for herbicidal activity against rape and barnyard grass. Compound B13 exhibited moderate herbicidal activity.     

Synthesis and characterization of some novel 2‐{2‐[1‐(3‐substituted‐phenyl)‐1H‐1,2,3‐triazol‐4‐yl‐] ethyl}‐1‐substituted‐1H‐benzo [d] imidazole derivatives

Synthesis of some novel 2‐{2‐[1‐(3‐substitutedphenyl)‐1H‐1,2, 3‐triazol‐4‐yl‐]ethyl)‐1H‐benzo[d]‐imidazole derivatives, by the condensation of o‐phenylenediamine with 3‐(1‐(3‐substituted‐phenyl)‐1H‐1,2,3‐triazol‐4‐yl) propanoic acid and then subsequent reactions with different substituted alkyl halides as electrophiles are mentioned. The synthesized compounds were characterized by ¹H NMR, EI‐MS and IR spectroscopic techniques.     

One‐pot synthesis of symmetrically disubstituted 3H‐phenoxazin‐3‐ones by selective oxidative condensation with LTA

A one‐pot synthesis of some new 2,8‐disubstituted 3H‐phenoxazin‐3‐ones from 4‐substituted‐2‐aminophenols through a selective oxidative condensation by lead tetraacetate in acetic acid is described.     

A general and versatile synthesis of 3‐phenylthio β‐lactams as lead molecules for 3‐methyl‐2‐azetidinones

Ketene‐imine cycloaddition using phosphorus oxychloride and benzenesulfonyl chloride under the described reaction conditions yielded trans 3‐phenylthio 2‐azetidinones in good yields. Desulfurization using Raney nickel and alkylation finally afforded trans 3‐methyl‐2‐azetidinones in a stereoselective manner.     

A facile regioselective synthesis of (5‐amino‐4‐cyano‐1h‐imidazol‐1‐yl) benzoic acids

A simple and efficient method was developped for the synthesis of 3‐(5‐amino‐4‐cyano‐1H‐imidazol‐1‐yl)‐4‐substituted benzoic acids 3 . These compounds were isolated by intramolecular cyclisation of the corresponding 3‐{[(Z)‐2‐amino‐1,2‐dicyano‐vinyl]amino}methyleneaminobenzoic acids in the presence of base.