Isotopic effect on tautomeric behavior of 5‐(2,6‐disubstituted‐aryloxy)‐tetrazoles

Isotopic effect on tautomeric behaviors of the synthesized 5‐phenoxy‐ (1a), 5‐(2,6‐dimethylphenoxy)‐ (1b), 5‐(2,6‐diisopropylphenoxy)‐ (1c), 5‐(2,6‐dimethoxyphenoxy)‐ (1d) and 5‐(4‐methylphenoxy)‐tetrazole (1e) were investigated in DMSO‐d₆ by adding one drop of D₂O. Among 1a–e, 1a, 1d and 1e show small rotational barrier around C5? O1 and O1? C6 while in 1b and 1c there are distinguishable rotational barrier about that bonds. The ¹H NMR spectra of 1b and 1c show slightly different chemical shifts for two methyl and isopropyl groups on those phenyl ring, respectively, while the chemical shifts difference (Δδ) between two methyl and two isopropyl groups were enhanced by adding D₂O. The ¹³C NMR spectra of 1b show two overlapped singlets for methyl groups after adding D₂O. Representatively, the calculations of compound 1c were performed with GAUSSIAN‐03and the rotational barrier about C5? O1 and between isopropyl group and phenyl ring in 1c was calculated with B3LYP/6‐31G(d) basis set. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of 2‐(sulfamoylphenyl)‐4′‐(iminoaryl/hetroaryl)‐4‐(4′′‐hydroxyphenyl)‐thiazoles and their O‐glucosides

In continuation of our work, we synthesized 2‐(sulfamoylphenyl)‐4′‐amino‐4‐(4″‐hydroxyphenyl)‐thiazole ( 3a ), which were reacted with various (aryl/hetroaryl) aldehyde to form 2‐(sulfamoylphenyl)‐4′‐(iminoaryl/hetroaryl)‐4‐(4″‐hydroxyphenyl)‐thiazoles ( 4a , 4b , 4c , 4d , 4e , 4f ). Glucosylation of compounds ( 4a , 4b , 4c , 4d , 4e , 4f ) have been done by using acetobromoglucose as a glucosyl donor to afford 2‐(sulfamoylphenyl)‐4′‐(iminoaryl/hetroaryl)‐4‐(2,3,4,6‐tetra‐O‐acetyl‐4″‐O‐β‐D ‐glucosidoxyphenyl)‐thiazoles ( 5a , 5b , 5c , 5d , 5e , 5f ), further on deacetylation to produce 2‐(sulfamoylphenyl)‐4′‐(iminoaryl/hetroaryl)‐4‐(4″‐O‐β‐D ‐glucosidoxyphenyl)‐thiazoles ( 6a , 6b , 6c , 6d , 6e , 6f ). The compounds are confirmed by FTIR, ¹H‐NMR, ¹³C‐NMR, and ES‐Mass spectral analysis. J. Heterocyclic Chem., (2011).     

NIR‐Absorbing Donor–Acceptor Based 1,1,4,4‐Tetracyanobuta‐1,3‐Diene (TCBD)‐ and Cyclohexa‐2,5‐Diene‐1,4‐Ylidene‐Expanded TCBD‐Substituted Ferrocenyl Phenothiazines

A series of unsymmetrical (D‐A‐D₁, D₁‐π‐D‐A‐D₁, and D₁‐A₁‐D‐A₂‐D₁; A=acceptor, D=donor) and symmetrical (D₁‐A‐D‐A‐D₁) phenothiazines ( 4 b , 4 c , 4 c′ , 5 b , 5 c , 5 d , 5 d′ , 5 e , 5 e′ , 5 f , and 5 f′ ) were designed and synthesized by a [2+2] cycloaddition–electrocyclic ring‐opening reaction of ferrocenyl‐substituted phenothiazines with tetracyanoethylene (TCNE) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ). The photophysical, electrochemical, and computational studies show a strong charge‐transfer (CT) interaction in the phenothiazine derivatives that can be tuned by varying the number of TCNE/TCNQ acceptors. Phenothiazines 4 b , 4 c , 4 c′ , 5 b , 5 c , 5 d , 5 d′ , 5 e , 5 e′ , 5 f and 5 f′ show redshifted absorption in the λ =400 to 900 nm region, as a result of a low HOMO–LUMO gap, which is supported by TD‐DFT calculations. The electrochemical study exhibits reduction waves at low potential due to strong 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) and cyclohexa‐2,5‐diene‐1,4‐ylidene‐expanded TCBD acceptors. The incorporation of cyclohexa‐2,5‐diene‐1,4‐ylidene‐expanded TCBD stabilized the LUMO energy level to a greater extent than TCBD.     

A Novel Synthesis of 1‐Aryl‐6‐bromo‐3‐(5‐ethylthio‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐pyrazolo[4,3‐b]quinolin‐9(4H)‐ones via Thermal Cyclization of 4‐Azidopyrazoles

2‐Aryl‐hydrazononitriles 3a , 3b , 3c were prepared by coupling 3‐ethylthio‐5‐cyanomethyl‐4‐phenyl‐1,2,4‐triazole ( 1 ) with diazonium salts 2a , 2b , 2c . Reacting 3a , 3b , 3c with both ethyl bromoacetate ( 4a ) and 4‐bromobenzyl bromide ( 4b ) in DMF, in the presence of K₂CO₃, at 80 °C for 3–4 h, gave the corresponding 4‐amino‐pyrazoles 6a , 6b , 6c , 6d , 6e , 6f . Diazotization of 6a , 6b , 6c , 6d , 6e , 6f , followed by reaction with NaN₃, leads to the formation of 4‐azidopyrazoles 8a , 8b , 8c , 8d , 8e , 8f , a new heterocyclic ring system. Interestingly, fusion of 4‐azidopyrazoles 8d , 8e , 8f at temperature higher than their melting points with 5 °C for 2 min did not give the expected fused pyrazolo[4,3‐c]isoxazoles 9 but furnished instead the novel pyrazolo[4,3‐b]quinolinones 10a , 10b , 10c , in high yields.     

Synthesis and isolation of bromo‐β‐carbolines obtained by bromination of β‐carboline alkaloids

β‐Carbolines ( 1–5 ) undergo electrophilic aromatic substitution with N‐bromosuccinimide under different experimental conditions. Although 6‐bromo‐nor‐harmane ( la ) obtained by bromination of nor‐harmane ( 1 ) was isolated and fully characterized sometime ago, the other bromoderivatives of nor‐harmane ( 1b‐1e ) and harmane ( 2a‐2e ) were partially described as part of the reaction mixtures. The preparation and subsequent isolation, purification and full characterization of 1b, 1c, 1d, 1e, 2a, 2b, 2c, 2d, 2e are reported (mp, R _f, ¹H‐nmr, ¹³C‐nmr and ms) together with the preparation, isolation and charaterization, for the first time, of the bromoderivatives obtained from harmine ( 3a‐3e ), harmol ( 4a, 4b ) and 7‐acetylharmol ( 5a‐5c ). As brominating reagent N‐bromosuccinimide and N‐bromosuccinimide‐silica gel in dichloromethane and in chloroform as well as the β‐carboline ‐ N‐bomosuccinimide solid mixture have been used and their uses have been compared. Semiempirical AMI and PM3 calculations have been performed in order to predict reactivity in terms of the energies of HOMO, HOMO‐LUMO difference and in terms of the charge density of β‐carbolines ( 1–5 ) and bromo‐β‐carbolines ( 1a‐1e, 2a‐2e, 3a‐3e, 4a, 4b, 5a, 5b and 5c ) (Scheme 1). Theoretical and experimental results are discussed briefly.     

An efficient synthesis of 5‐aryl‐4,5‐dihydro‐3‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐1‐(4‐phenylthiazol‐2‐yl)pyrazoles

Some new target products 5‐aryl‐4,5‐dihydro‐3‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐1‐(4‐phenylthiazol‐2‐yl)pyrazoles 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j have been synthesized by reaction of 2‐bromo‐1‐phenylethanone and compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j which were prepared from the combination of thiosemicarbazide and (E)‐3‐aryl‐1‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐prop‐2‐en‐1‐ones 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j . All the structures were established by MS, IR, CHN, and ¹H NMR spectra data. Synthesis of structure diversity is applied. J. Heterocyclic Chem., (2011).     

Synthesis and Optical Properties of Novel Fluorescence‐Traced Benzimidazolium Bromides

Seven novel fluorescence‐traced 1‐aryl‐2‐substituted‐3‐allyl‐1H‐benzimidazolium bromides ( 5a , 5b , 5c , 5d , 5e , 5f , 5g ) were synthesized by alkylation and quaternization of compounds 1‐aryl‐2‐substituted‐1H‐benzimidazoles ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) with excess allyl bromide in acetonitrile at refluxing temperature. Their structures were characterized by ¹H‐NMR, MS, and elemental analysis. They emit violet‐blue light (λ^Em_max = 386–438 nm) with fluorescence quantum yields of 0.54 to 0.75 in aqueous solution.     

Quinolone Analogs 14: Synthesis of Antimalarial 1‐Aryl‐3‐(4‐quinolon‐2‐yl)ureas and Related Compounds

The 4‐quinolone‐2‐carbohydrazide 6a was converted into 1‐aryl‐3‐(4‐quinolon‐2‐yl)ureas 5a , 5b , 5c , 5d , 5e , 1‐aryl‐3‐(4‐quinolon‐2‐yl)imidazolidine‐2,4‐diones 9a , 9b , and N‐(4‐quinolon‐2‐yl)carbamates 10a , 10b via 4‐quinolone‐2‐carbonylazide 7a . The 4‐methoxyquinoline‐2‐carbohydrazide 6b was also transformed into 1‐aryl‐3‐(4‐methoxyquinolin‐2‐yl)ureas 11a , 11b , 11c , 11d , 1‐aryl‐3‐(4‐methoxyquinolin‐2‐yl)imidazolidine‐2,4‐diones 12a , 12b , and N‐(4‐methoxyquinolin‐2‐yl)carbamates 13a , 13b via 4‐methoxyquinoline‐2‐carbonylazide 7b . Some of the 1‐aryl‐3‐(4‐quinolon‐2‐yl)ureas 5a , 5b , 5c , 5d , 5e showed the in vitro antimalarial activity to chloroquine‐resistant Plasmodium falciparum, wherein IC₅₀ was 0.93 to 4.00 μM.     

Major‐Groove‐Halogenated DNA: The Effects of Bromo and Iodo Substituents Replacing H−C(7) of 8‐Aza‐7‐deazapurine‐2,6‐diamine or H−C(5) of Uracil Residues

Oligonucleotides containing halogenated `purine' and pyrimidine bases were synthesized. Bromo and iodo substituents were introduced at the 7‐position of 8‐aza‐7‐deazapurine‐2,6‐diamine (see 2b , c ) or at the 5‐position of uracil residues (see 3b , c ). Phosphoramidites were synthesized after protection of 2b with the isobutyryl residue and of 2c with the benzoyl group. Duplexes containing the residues 2b or 2c gave always higher T<sub>m</sub> values than those of the nonmodified counterparts containing 2′‐deoxyadenosine, the purine‐2,6‐diamine 2′‐deoxyribonucleoside ( 1 ), or 2a at the same positions. Six 2b residues replacing dA in the duplex 5′‐d(TAGGTCAATACT)‐3′ ( 11 )⋅5′‐d(AGTATTGACCTA)‐3′ ( 12 ) raised the T<sub>m</sub> value from 48 to 75° (4.5° per modification (Table 3)). Contrary to this, incorporation of the 5‐halogenated 2′‐deoxyuridines 3b or 3c into oligonucleotide duplexes showed very little influence on the thermal stability, regardless of which `purine' nucleoside was located opposite to them (Tables 4 and 5). The positive effects on the thermal stability of duplexes observed in DNA were also found in DNA⋅RNA hybrids or in DNA with parallel chain orientation (Tables 8 and 9, resp.).     

Synthesis of New Derivatives of 4‐(4,7,7‐Trimethyl‐7,8‐dihydro‐6H‐benzo[b]pyrimido[5,4‐e][1,4]thiazin‐2‐yl)morpholine

Cyclocondensation of 5‐amino‐6‐methyl‐2‐morpholinopyrimidine‐4‐thiol ( 1 ) and 2‐bromo‐5,5‐dimethylcyclohexane‐1,3‐dione ( 2 ) under mild reaction condition afforded 4,7,7‐trimethyl‐2‐morpholino‐7,8‐dihydro‐5H‐benzo[b ]pyrimido[5,4‐e ][1,4]thiazin‐9(6H )‐one ( 3 ). The ¹H and ¹³C NMR data of compound ( 3 ) are demonstrated that this compound exists primarily in the enamino ketone form. Reaction of compound ( 3 ) with phosphorous oxychloride gave 4‐(9‐chloro‐4,7,7‐trimethyl‐7,8‐dihydro‐6H‐benzo[b ]pyrimido[5,4‐e ][1,4]thiazin‐2‐yl)morpholine ( 4 ). Nucleophilic substitution of chlorine atom of compound ( 4 ) with typical secondary amines in DMF and K₂CO₃ furnished the new substituted derivatives of 4‐(4,7,7‐trimethyl‐7,8‐dihydro‐6H‐benzo[b ]pyrimido[5,4‐e ][1,4]thiazin‐2‐yl)morpholine ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h ). All the synthesized products were characterized and confirmed by their spectroscopic and microanalytical data.     

Reaction of N‐(phenyl and methyl)‐C‐arylnitrones with DMAD in ionic liquid: Efficient synthesis of Δ4‐isoxazolines

Facile synthesis of N‐(methyl and phenyl)‐Δ⁴‐isoxazolines via the reaction of (Z)‐N‐(methyl and phenyl)‐C‐arylnitrones with dimethyl acethylenedicarboxylate, DMAD, in ionic liquid is described. (Z)‐N‐methyl‐C‐arylnitrones afforded the high yield of N‐methyl‐Δ⁴‐isoxazolines 4a , 4b , 4c , 4d , 4e in ionic liquid, [bmim]BF₄, at room temperature. However, the reaction of (Z)‐N‐phenyl‐C‐arylnitrones with DMAD afforded the mixtures of cis and trans isomers of related N‐phenyl‐Δ⁴‐isoxazolines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j ) under these conditions. J. Heterocyclic Chem., (2012).     

Donor–acceptor alternating π‐conjugated polymers containing Di(thiophen‐2‐yl)pyrene and 2,5‐Bis(2‐octyldodecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione for organic thin‐film transistors

New diketopyrrolopyrrole (DPP)‐containing conjugated polymers such as poly(2,5‐bis(2‐octyldodecyl)‐3‐(5‐(pyren‐1‐yl)thiophen‐2‐yl)‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione) (P(DTDPP‐alt‐(1,6)PY)) and poly(2,5‐bis(2‐octyldodecyl)‐3‐(5‐(pyren‐2‐yl)thiophen‐2‐yl)‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione) (P(DTDPP‐alt‐(2,7)PY)) were successfully synthesized via Suzuki coupling reactions under Pd(0)‐catalyzed conditions. P(DTDPP‐alt‐(2,7)PY), incorporating 2,5‐bis(2‐octyldodecyl)‐3,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione (DTDPP) at the 2,7‐position of a pyrene ring showed a lower band‐gap energy (E. = 1.65 eV) than the 1,6‐substituted analog, P(DTDPP‐alt‐(1,6)PY) (E = 1.71 eV). The energies of the molecular frontier orbitals of the substituted polymers were successfully tuned by changing the anchoring position of DTDPP from the 1,6‐ to the 2,7‐position of the pyrene ring. An organic thin‐film transistor fabricated using the newly synthesized P(DTDPP‐alt‐(2,7)PY), as a semiconductor material exhibited a maximum mobility of up to 0.23 cm² V^?1 s^?1 (I_on/off ～ 10⁶), which was much larger than that obtained using P(DTDPP‐alt‐(1,6)PY). This distinction is attributed to morphological differences in the solid state arising from differences between the geometrical configurations of DTDPP and the pyrene ring. In addition, the organic phototransistor devices made of P(DTDPP‐alt‐(2,7)PY) showed interesting photoinduced enhancement of drain current when irradiating the excitation light whose intensity is very small. Based on the photoinduced effect on I_DS, photocontrolled memory could be realized under the variation of gate voltages. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Full Characterization and some reactions of 1‐(2‐adamantyl)‐3‐(1‐adamantyl)aziridin‐2‐one

We found that 1‐(2‐adamantyl)‐3‐tert‐butylaziridin‐2‐one ( 5a ) is unstable. It slowly decomposes at room temperature, although detectable by IR spectroscopy (1840 cm^?1 band in CCl₄). On the other hand, a closely related analogue, 1‐(2‐adamantyl)‐3‐(1‐adamantyl)aziridin‐2‐one ( 5b ), is very stable, in concurrence with an earlier report [1]. We fully characterized aziridinone 5b , identified its thermal decomposition products ( 7 and 8 ) and reacted it with two aprotic ionic (tBuO^? and HO^?) and one protic non‐ionic nucleophile (benzylamine). All three products ( 9b , 10 , and 11 ) result from exclusive cleavage of the lactam (1‐2) bond.     

An Innovative Protocol for the Synthesis of 3‐(Pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles and 9,10‐Dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles

Herein, we present an innovative, novel, and highly convenient protocol for the synthesis of 3‐(pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ) and 9,10‐dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles ( 10a , 10b , 10c , 10d , 10e ), which have been delineated from the reaction of 4‐sec‐amino‐2‐oxo‐6‐aryl‐2H‐pyran‐3‐carbonitrile ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) and 4‐sec‐amino‐2‐oxo‐5,6‐dihydro‐2H‐benzo[h]chromene‐3‐carbonitriles ( 9a , 9b , 9c , 9d , 9e ) with 2‐acetylpyridine ( 5 ) through the ring transformation reaction by using KOH/DMF system at RT. The salient feature of this procedure is to provide a transition metal‐free route for the synthesis of asymmetrical 1,3‐teraryls like 3‐(pyridin‐2‐yl)‐5‐sec‐aminobiphenyl‐4‐carbonitriles ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ) and 9,10‐dihydro‐3‐(pyridine‐2‐yl)‐1‐sec‐aminophenanthrene‐2‐carbonitriles ( 10a , 10b , 10c , 10d , 10e ). The novelty of the reaction lies in the creation of an aromatic ring from 2H‐pyran‐2‐ones and 2H‐benzo[h]chromene‐3‐carbonitriles via two‐carbon insertion from 2‐acetylpyridine ( 5 ) used as a source of carbanion.     

Synthesis and Biological Activity of O‐Methyl Methyl 1‐(Substituted Phenoxyacetoxy)‐1‐(thien‐2‐yl)methylphosphinates

A series of novel O‐methyl methyl 1‐(substituted phenoxyacetoxy)‐1‐(thien‐2‐yl)methylphosphinates 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h were synthesized. Their structures were confirmed by IR, ¹H NMR, mass spectroscopy, and elemental analyses. The results of preliminary bioassays show that some of the title compounds exhibit moderate to good herbicidal and fungicidal activities. For example, the title compounds 5c , 5d , and 5g possess 90–100% inhibition against the tested plants at the concentration of 10 mg/L and 100 mg/L, whereas the title compounds 5a , 5b , 5c , and 5h possess 70–94% inhibition against Phyricularia grisea and Sclerotinia sclerotiorum at the concentration of 50 mg/L.     

Mercuric Acetate Mediated Oxidative Cyclization of (2E, 4E)‐1‐(2‐Hydroxyphenyl)‐5‐phenylpenta‐2,4‐dien‐1‐ones: Synthesis of (Z)‐2‐((E)‐3‐Phenylallylidene)benzofuran‐3(2H)‐ones

(2E,4E)‐1‐(2‐Hydroxyphenyl)‐5‐phenylpenta‐2,4‐dien‐1‐ones 1a , 1b , 1c , 1d , 1e on oxidative cyclization with mercuric acetate in dimethylsulphoxide have provided (Z)‐2‐((E)‐3‐phenylallylidene)benzofuran‐3(2H)‐ones 2a , 2b , 2c , 2d , 2e in good yields.     

Synthesis of 2‐amino‐4‐aryl‐7,7‐dimethyl‐5‐oxo‐4H‐5,6,7,8‐tetrahydrobenzo[b]pyran derivatives in ionic liquid medium

In this paper, preparation of 2‐Amino‐4‐aryl‐7,7‐dimethyl‐5‐oxo‐4H‐5,6,7,8‐tetrahydrobenzo[b]pyran derivatives from aromatic aldehyde, malononitrile or cyanoacetate and 5,5‐dimethyl‐1,3‐cyclohexanedione in ionic liquid [bmim⁺][BF₄^?] was described. Compared with other methods, this new method has the advantages of easier work‐up, milder reaction conditions, high yields and environmentally benign procedure.     

New N‐(Aryl)‐5‐((quinolin‐8‐yloxy)methyl)‐1,3,4‐oxa/Thiadiazol‐2‐amines and 4‐Aryl‐5‐((quinolin‐8‐yloxy)methyl)‐2H‐1,2,4‐triazole‐3(4H)‐thiones,Synthesis and Characterization

In this study, methyl 2‐(quinolin‐8‐yloxy) acetate ( 2 ) obtained by reaction of 8‐hydroxyquinoline ( 1 ) with methyl chloroacetate was condensed with hydrazine hydrate to afford the carbohydrazide ( 3 ). Thio/semicarbazide derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) were obtained by treatment of the 3 with substituted phenyl iso/thioisocyanates. The 4a , 4b , 4c , 4d , 4e , 4f , 4g on acidic and basic intramolecular cyclization led to N‐(aryl)‐5‐((quinolin‐8‐yloxy)methyl)‐1,3,4‐oxa/thiadiazol‐2‐amines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g ) and 4‐aryl‐5‐((quinolin‐8‐yloxy)methyl)‐2H‐1,2,4‐triazole‐3(4H)‐thiones ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ), respectively. All the synthesized compounds were characterized by spectroscopic techniques and elemental analyses. The thiosemicarbazide ( 4c ) was also confirmed by X‐ray crystallography.     

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.     

Fused Heterocycles: Synthesis and Antitubercular Activity of Novel 6‐Substituted‐2‐(4‐methyl‐2‐substituted phenylthiazol‐5‐yl)H‐imidazo[1,2‐a]pyridine

A series of 6‐substituted‐2‐(4‐methyl‐2‐substituted phenylthiazol‐5‐yl)H‐imidazo[1,2‐a]pyridine derivatives 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l is described. The antitubercular activity of the synthesized compounds was determined against Mycobacterium smegmatis MC² 155 strain. From the activity result, it was found that the phenyl or 4‐fluorophenyl group at 2 position of thiazole nucleus and bromo substituent at 6 position of imidazo[1,2‐a]pyridine showed good antitubercular activity.