bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of optically active 1,2,3‐substituted‐1,4,5,6‐tetrahydro‐7H‐indolones
Authors: Nitti P. , Pitacco G. , Pizzioli A. , Valentin E.
Published: April 2009

Trisubstituted 1,4,5,6,‐tetrahydro‐7H‐indolones are obtained in a one‐pot synthesis from conjugated nitroolefins and α‐ketoenamines derived from α‐amino esters and cyclohexane‐1,2‐dione. In some cases bicyclo[3.2.1]octan‐8‐one and 1,2‐oxazine N‐oxide derivatives are isolated.
Synthesis of novel pyridazino[3,4‐b]quinoxalines
Authors: Kim Ho Sik , Kim Eun Kyoung , Kim Sung Sik , Park Yong Tae , Hong Young Seuk , Kurasawa Yoshihisa
Published: April 2009

The pyridazino[3,4‐b]quinoxaline 12 was synthesized by the cyclization of the α‐arylhydrazonoacyl‐hydrazide 11. The reaction of compound 12 with phosphoryl chloride gave pyridazino[3,4‐b]quinoxaline 13, whose reactions with sodium azide or cyclic secondary amines provided pyridazino[3,4‐b]quinoxalines 14,17 and 18, respectively. The acylhydrazide 15 was also cyclized to pyridazino[3,4‐b]quinoxaline 16.
Basicities of thiazole heterocyclic compounds and the reaction of 3‐methyl‐2‐methylimino‐Δ4‐thiazolines with ethyl bromoacetate and 2‐bromoacetophenone
Authors: Kim Dong Chan , Yoo Kyung Ho , Shin Kye Jung , Park Sang Woo , Kim Dong Jin
Published: April 2009

The pKa′s of several thiazole heterocyclic compounds have been determined and represent products with significantly high values. Because of their high basicities, sometimes these compounds were able to act as not only nucleophiles but also strong organic bases. 4‐Substituted‐3‐methyl‐2‐methylimino‐Δ4‐thiazolines 5a‐d reacted with ethyl bromoacetate in refluxing benzene, giving the corresponding N‐alkylated salts 8a‐d, while the products obtained from the reaction with 2‐bromoacetophenone in the presence of base were pyrrolothiazines 10b‐d.
1,2,3‐Triazolo[4,5‐d]‐1,2,4‐triazolo[4,3‐b]pyridazines
Authors: Biagi Giuliana , Giorgi Irene , Livi Oreste , Manera Clementina , Scartoni Valerio
Published: April 2009

Some new 1,2,3‐triazolo[4,5‐d]‐1,2,4‐triazolo[4,3‐b]pyridazines were prepared starting from the corresponding 1,2,3‐triazolo[4,5‐d]pyridazines via the formation of the 1,2,4‐triazole ring, by condensation of an appropriate monocarbon fragment with the 4‐hydrazino substituent and the nitrogen atom in the 5 position of the heterocycle. Condensation of 4‐phenylhydrazino substituted derivatives with formic acid gave zwitterionic compounds.
Synthesis of alkyl 2‐phenylnicotinates
Authors: Yamauchi M. , Shirota M. , Tsugane A.
Published: April 2009

Various alkyl 6‐ethoxy‐2‐phenyl‐5,6‐dihydro‐4H‐pyran‐3‐carboxylate 2A are easily converted to the corresponding nicotinates 3 by reaction with hydroxylamine hydrochloride in refluxing absolute ethanol.
Synthesis of imidazo[4,5‐b]pyridines from aminoimidazolecarbaldehydes
Authors: Perandones Francisco , Soto Jose L.
Published: April 2009

4‐Amino‐1,2‐dimethylimidazole‐5‐carbaldehyde (1) and 5‐amino‐1‐methylimidazole‐4‐carbaldehydes 3 were prepared by reduction of the corresponding aminoimidazolecarbonitriles 2 and 4. Condensation of 1 and 3 with carbonitriles, ketones and polyfunctional carbonyl compounds bearing the‐CH2CO‐moiety afforded to the imidazo[4,5‐b]pyridine derivatives.
Gas phase thermolysis of pyrazolines. 5. Electronic structure and gas phase thermolysis of tetrazole derivatives studied by photoelectron spectroscopy
Authors: Awadallah Adel , Kowski Klaus , Rademacher Paul
Published: April 2009

The photoelectron spectra of substituted tetrazoles 1–3, 1,4‐dihydro‐5H‐tetrazol‐5‐ones 4–9, and 1,4‐dihydro‐5H‐tetrazole‐5‐thiones 10–15 have been recorded. Based on PM3 and some ab initio calculations, the ionization potentials have been assigned to molecular orbitals. Gas‐phase thermolyses of 1–15 have been studied by real‐time gas analysis controlled by photoelectron spectroscopy. Compounds 1 and 2 lose formaldehyde and thioformaldehyde, respectively, leaving unsubstituted tetrazole (16), which decomposes mainly through extrusion of a nitrogen molecule and formation of cyanamide. Thiirane is split off from 3, and the remaining molecule decomposes into smaller products. Compounds 4–9 are cleaved by [3+2] cycloreversion to isocyanates and azides. Some of the unsymmetrically substituted compounds exhibit a marked selectivity in this reaction. For thiones 10–15 [3+2] cycloreversion is the main way of decomposition affording isothiocyanates and azides. In addition, the sulfur atom can split off and dimerize or abstract hydrogen atoms to form hydrogen sulfide. Some products like thiirene, formaldehyde, thioformaldehyde and acetaldehyde are generated solely from substituents. Photoelectron spectroscopy proved to be an excellent method for such thermolysis studies.
Synthesis and DNA binding properties of bis‐9‐acridinyl derivatives containing mono‐, di‐and tetra‐viologen units as a connector of bis‐intercalators
Authors: Takenaka Shigeori , Sato Hirotaka , Ihara Toshihiro , Takagi Makoto
Published: April 2009

Bis‐9‐acridinyl derivatives 1–3 containing mono‐, di‐and tetra‐viologen units as a rigid connector were synthesized. The binding studies of these intercalators for natural and synthetic DNAs showed that these compounds act as bis‐intercalators where viologen moieties lie in the minor groove of the DNA duplex. The DNA binding affinity of the intercalators was enhanced with an increase in the number of the viologen unit.
Furopyridines. XX. Wittig‐horner reaction of a phosphonate of reissert analogues of furo[3,2‐c]‐, ‐[2,3‐c]‐ and ‐[3,2‐b]pyridines
Authors: Shiotani Shunsaku , Tsukamoto Youichi , Kitagawa Yasuyuki
Published: April 2009

Furo[3,2‐c]‐(1a), ‐[2,3‐c]‐ (1b) and ‐[3,2‐b]pyridine (1c) were reacted with isopropyl chloroformate and trimethyl phosphite to give dimethyl 5‐isopropoxycarbonyl‐4,5‐dihydrofuro[3,2‐c]pyridine‐4‐phosphonate (2a), dimethyl 6‐isopropoxycarbonyl‐6,7‐dihydrofuro[2,3‐c]pyridine‐7‐phosphonate (2b) and dimethyl 4‐isopropoxycarbonyl‐4,7‐dihydrofuro[3,2‐b]pyridine‐7‐phosphonate (2c) as unstable syrups. Reaction of 2b and 2c with n‐butyllithium and then with benzaldehyde, p‐methoxybenzaldehyde, p‐cyanobenzalde‐hyde or propionaldehyde afforded the normal Wittig reaction products 5b‐H, 5b‐OMe, 5b‐CN, 5b‐Et, 5c‐H, 5c‐H, 5c‐OMe and 5c‐CN, except for 2b with propionaldehyde. While, the same reactions of compound 2a and the reaction of 2b with propionaldehyde afforded the unexpected products, 5‐isopropoxycar‐bonylfuro[3,2‐c]pyridinio‐4‐aryl‐(or ethyl)methoxides 3a‐H, 3a‐OMe, 3a‐CN and 3a‐Et, 4‐(1′‐aryl(or ethyl)‐1′‐hydroxymethyl)furo[3,2‐c]pyridines 4a‐H, 4a‐OMe, 4a‐CN and 4a‐Et accompanying formation of the normal products. Treatment of the normal Wittig reaction products with lithium diisopropylamide and then with acetone gave the derivatives alkylated at the 2‐or the benzylic positions.
Photochemical reactions of 1‐methyl‐4,6‐diaryl‐2(1H)‐pyrimidinones in the presence of thiols
Authors: Nishio Takehiko , Kato Michiyo
Published: April 2009

Photochemical reactions of 1‐methyl‐4,6‐diaryl‐2(1H)pyrimidinones 1a‐b in the presence of thiols 2 are described. Irradiation of 1‐methyl‐4,6‐diaryl‐2(1H)‐pyrimidinones 1a‐b in benzene in the presence of thiols 2 gave the unexpected 2:1‐adducts, 3‐methyl‐4,6‐diaryl‐5‐aralkylthio‐6‐(1′‐methyl‐4′,6′‐diaryldihydro‐pyrimidin‐2‐on)yl‐1,3‐diazabicyclo[2.2.0]hexan‐2‐ones 3‐6, of 1 and 2, whereas irradiation of 1a‐b alone in benzene resulted in recovery of the unchanged 1a‐b.
Study on the structures of 2‐substituted iminothiazolidine derivatives
Authors: Sakae Masatoshi , Katsurada Masanori , Watanabe Mayumi , Yoneda Fumio , Nishigaki Sadao , Ishida Toshimasa
Published: April 2009

The reaction of 2‐bromoethylamine 1 with methylisothiocyanate 2 under mild condition gave 2‐methyl‐amino‐2‐thiazoline 3 as the major product together with two kinds of byproducts, 3‐(N‐methylthiocar‐bamoyl)‐2‐methyliminothiazolidine 4 and N,N′‐dimethyl‐N‐(2‐thiazolin‐2‐yl)thiourea 5. Thermal isomer‐ization of 5 to 4 was observed. The structures of the byproducts were confirmed by X‐ray crystallography.
Synthesis of unsymmetrically substituted dodecakis(trifluoroethoxy)‐phthalocyaninato vanadyl complexes
Authors: Tian Minquan , Wada Tatsuo , Sasabe Hiroyuki
Published: April 2009

Three novel unsymmetrical vanadyl dodecakis(2,2,2‐trifluoroethoxy)phthalocyaninates with nitro, amino or with no substitution were synthesized by a statistical condensation of 3,4,5,6‐tetrakis(2,2,2‐trifluoroethoxy)phthalonitrile with 4‐nitro, 4‐amino or 4‐unsubstituted phthalonitrile, and separated by common column chromatography. These highly soluble phthalocyanines were characterized by elemental analysis, ir and 1H‐nmr, uv‐visible and fast‐atom‐bombardment mass spectroscopy. Their uv‐visible absorption spectra in solution and in doped poly(methyl methacrylate) films showed that they were less aggregated unsymmetrical phthalocyanines.
1,3‐Dipolar cycloaddition reactions of cyclooctyne with pyridinium dicynomethylides
Authors: Matsumoto Kiyoshi , Ohta Ryuji , Uchida Takane , Nishioka Hiroyasu , Yoshida Maki , Kakehi Akikazu
Published: April 2009

Cyclooctyne smoothly underwent 1,3‐dipolar cycloaddition with pyridinium dicyanomethylides to afford the corresponding indolizines (8‐cyario‐7‐azatricyclo[7.6.0.02,7]pentadeca‐1,3,5,8‐tetraenes) in excellent yields.
Direct determination of pKa values of cationic acids conjugated to heterocyclic amine N‐oxides in polar aprotic and amphiprotic solvents
Authors: Chmurzyński Lech , Wawrzyniak Grażyna , Warnke Zygmunt , Pawlak Zenon
Published: April 2009

The applicability of the direct method of pKa determination in the case of protonated heterocyclic amine N‐oxides in a series of polar non‐aqueous (aprotic and amphiprotic) solvents has been tested. The method is based on the pH determination of the non‐aqueous solution of complex salt (the semiperchlorate in this case) formed by the N‐oxides studied. The direct method not only provides for quick (one data point per each pKa determined), but also relatively accurate estimates of acidic dissociation constants. It has been experimentally shown on the example of substituted pyridine N‐oxides that this method is precise enough in all studied non‐aqueous solvents when applied to compounds of not too low basicity (the pKa being of the order of 5 or higher). To prove this, the pKa values of protonated monocyclic N‐oxides obtained by the direct method have been compared with those resulting from the potentiometric titration curve. The agreement between the results found by using both methods is very good in most cases, the differences being within standard deviations. Based upon this observation it can be inferred that the pKa values of protonated bicyclic N‐oxides in solvents studied determined by using the direct method can be also considered reliable, especially in the case of polar aprotic solvents.
Intramolecular cyclization of amido acids into pyrrolidinothieno(or [1]benzothieno)[3]azepinediones
Authors: Othman Mohamed , Netchitailo Pierre , Decroix Bernard
Published: April 2009

The synthesis of pyrrolidino[2,1‐b]thieno[3,2(2,3)‐f][3]azepinediones 7a,b and pyrrolidino[2,1‐b]‐[1]benzothieno[3,2(2,3)‐f][3]azepinediones 7c,d are described starting from thiophenes or [1]benzothio‐phenes acetic acids. Their selective reduction using triethylsilane led to the corresponding azepinones 17a‐d.
Synthesis of certain alkenyl purines and purine analogs as inhibitors of tumor necrosis factor alpha (TNFα)
Authors: Rao T. Sudhakar , Ojwang Joshua O. , Marshall Hélène B. , Revankar Ganapathi R.
Published: April 2009

The preparation of 2‐penten‐1‐yl and 3‐methyl‐2‐buten‐1‐yl derivatives of adenine 2a,b, 7‐deazaadenine 2c,d, 2‐aminopurine 4a,b and 5a,b, 4‐aminopyrazolo[3,4‐d]pyrimidine 7a,b and 7‐amino‐v‐triazolo‐[4,5‐d]pyrimidine 8a–10a and 8b‐10b is described. The synthesis of compounds 2a‐d was accomplished by the functional group transformation reaction, whereas the synthesis of 4a‐8a and 4b‐8b was performed by the alkylation of the sodium salt of the heterocycles with alkenyl bromides. These alkenyl derivatives prepared as congeners of pentoxifylline (methylxanthine) were evaluated for their anti‐tumor necrosis factor a activity in human monocytic leukemia cells. Only compounds 7a and 7b exhibited significant activity and a poor toxicity profile in this assay. In peripheral blood mononuclear cells, compounds 7a and 7b, inhibited tumor necrosis factor a production in a dose dependent manner.
Alkyl 2‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl)amino‐3‐dimethylaminopropenoates in the synthesis of heterocyclic systems
Authors: Strah Sonja , Stanovnik Branko , Grdadolnik Simona Golič
Published: April 2009

Alkyl 2‐(2‐benzoyl‐2‐ethoxycarbonyl‐1‐ethenyl)amino‐3‐dimethylaminopropenoates 4a,b were prepared. They react with C‐nucleophiles such a 2‐pyridinylacetonitrile 5 and methyl‐2‐quinolinylacetate 8, cyclohexane‐1,3‐dione 10 and its derivatives 12 and 14, resorcinol derivative 16, 2‐naphtol 18, 2‐pyranone derivatives 20 and 22, and 4‐hydroxypyridin‐2(1H)‐one 24, to form substituted amino derivatives of quinolizine 6, benzo[c]quinolizine 9, tetrahydrobenzopyran‐2‐one 11, 13, 15, naphto[2,1‐b]pyran‐3‐one 19, pyranopyranones 21, 23, and pyrano[3,2‐c]pyridine 25.
Unusual sensitivity to the concentration of ethanol in the boron trifluoride/ethanol‐catalyzed synthesis of 5,10,15,20‐tetrakis‐(4‐cyano‐2,6‐dimethylphenyl)porphyrin by the lindsey method
Authors: Steiger Beat , Anson Fred C.
Published: April 2009

The boron trifluoride/ethanol‐catalyzed condensation of 4‐cyano‐2,6‐dtmethylbenzaldehyde 1b with pyrrole by the Lindsey method to give the new, ortho‐disubstituted 5,10,15,20‐tetrakis(4‐cyano‐2,6‐dimethylphenyl)porphyrin 2 was found to be highly sensitive to the concentration of ethanol. In the absence of ethanol the yield of porphyrin is only 1%. Yields can be increased to 20–25% with ethanol concentrations of 0.05–0.1% (v/v) but they decrease rapidly at higher concentrations of ethanol. Optimized procedures for the preparation of both 1b and 2 are described and the newly synthesized molecules are characterized by nmr (1H and 13C), mass spectra and elemental analysis.
Porphyrins with exocyclic rings. Part 8. Synthesis of nitrogen‐15 and carbon‐13 labeled 2,3:7,8:12,13:17,18‐tetrabutanoporphyrin
Authors: Chen Shaohua , Lash Timothy D.
Published: April 2009

Nitrogen‐15 labeled butyl 4,5,6,7‐tetrahydro‐2H‐isoindoIe‐1‐carboxylate was prepared via butyl iso‐cyanoacetate from 15N‐glycine in an overall 46% yield. This bicyclic intermediate was converted into nitrogen‐15 and carbon‐13 labeled 2,3:7,8:12,13:17,18‐tetrabutanoporphyrin, a useful model system for the sedimentary tetrahydrobenzoporphyrins.
A general synthetic route to 4‐substituted‐2,2′‐bithiophenes
Authors: Rasmussen Seth C. , Pickens Jason C. , Hutchison James E.
Published: April 2009

A new synthetic route to 4‐substituted‐2,2′‐bithiophenes has been developed utilizing 4‐bromo‐2,2′‐bithiophene (1). Formation of the bithienyllithium adduct via halogen‐metal exchange was found to be problematic and resulted in complex mixtures of products. The Grignard reagent of 1 can be obtained easily via the “entrainment” method, allowing the production of 4‐substituted‐2,2′‐bithiophenes (where sub‐stituent = octyl, hydroxyethyl, hydroxymethyl, carboxy, carbomethoxy, acetoxyethyl, and acetoxymethyl).
Saturated heterocycles. 251. Determination of σ+ values of heteroaryl‐substituted phenyl groups via ring‐chain tautomerism
Authors: Fülöp Ferenc , Forró Enikö , Bernáth Gábor , Miskolczi István , Vainiotalo Pirjo , Martinsen Aarne
Published: April 2009

The Hammett‐Brown electrophilic substituent constants σ+ for five heteroaryl‐substituted phenyl groups were estimated via the ring‐chain tautomeric equilibria of three sets of oxazolidines and 1,3‐oxazines in deuteriochloroform solution. For oxazolidines derived from norephedrine and norpseudoephedrine, the σ+ values were also determined via the gas‐phase ring‐chain equilibria, by means of mass spectrometry. The results show that the heteroaromatic substituents studied have a slight electron‐withdrawing character, with σ+ in the range ‐0.03 to 0.59. The gas‐phase σ+ values are significantly higher than the solution values.
The complete 1H and 13C chemical shift assignments of a cyclopropylpyrroloindole analog: Adozelesin
Authors: Walker G. S. , Fagemess P. E. , Farley K. A. , Mizsak S. A.
Published: April 2009

The 1H and 13C nmr spectral assignments of [7bR]‐N‐[2‐[(4,5,8,8a‐tetrahydro‐7‐methyl‐4‐oxocyclo‐propa[c]pyrrolo[3,2‐e]indol‐2(1H)‐ylcarbonyl]‐1H‐indol‐5‐yl]‐2‐benzofurancarboxamide (Adozelesin) (1) are described. Complete and unambiguous assignments of the hydrogen and carbon spectra were made using a combination of conventional homonuclear and gradient‐selected inverse‐detected heteronuclear nmr experiments: double quantum filtered 1H‐1H correlation spectroscopy (COSY), gradient‐selected heteronuclear single quantum coherence spectroscopy (gs‐HSQC), and gradient‐selected heteronuclear multiple bond coherence spectroscopy (gs‐HMBC). The enhanced sensitivity of these experiments allowed a smaller sample concentration and shorter spectral collection times for a full nmr analysis of this compound. The nmr data corroborates the published structure of this compound.
Synthesis and binding properties of 2H‐1‐benzopyran‐2 one fluorophore‐linked calcium channel antagonist nifedipine (1,4‐dihydropyridine) analogs
Authors: Padmanabhan Seetharamaiyer , Peri Ravikumar , Rutledge Aleta , Triggle David J.
Published: April 2009

Nifedipine analogs I, II and III with the 2H‐1‐benzopyran‐2‐one (coumarin) fluorophore linked at the 2, 2 and 6 and 4 positions of the dihydropyridine ring were synthesized by the modified Hantzch condensation procedures. Attempts to synthesize dihydropyridine with the fluorophore at position 3 (IV) were unsuccessful.
13C‐NMR study on the tautomerism of 3‐(arylhydrazono)methyl‐2‐oxo‐1,2‐dihydroquinoxalines between the hydrazone imine and diazenylenamine forms
Authors: Kurasawa Yoshihisa , Takano Akiko , Kato Kyoko , Kim Ho Sik , Okamoto Yoshihisa
Published: April 2009

The 13C‐nmr study was carried out for the tautomerism of the 3‐(arylhydrazono)methyl‐2‐oxo‐1,2‐dihy‐droquinoxalines 1a‐g and 2a‐e between the hydrazone imine A and diazenylenamine B forms, providing the carbon chemical shifts for the tautomers A and B of compounds 1a‐g and 2a‐e. The comparison of the carbon chemical shifts for the tautomer B of compounds 1d, 1f, and 2b in deuteriodimethyl sulfoxide with those in deuteriotrifluoroacetic acid showed that the C4a, C5, and diazenyl carbons were considerably shielded presumably due to the azo N‐deuteration in deuteriotrifluoroacetic acid.
Synthesis of 6‐substituted 1‐alkoxy‐5‐alkyluracils
Authors: Kim Dae‐Kee , Kim Young‐Woo , Kim Key H.
Published: April 2009

Synthesis of 6‐substituted 1‐alkoxy‐5‐alkyluracils 2a‐c have been achieved from readily accessible 2‐alkyl‐3,3‐di(methylthio)acryloyl chlorides 4a,b in high overall yields. Treatment of 4a,b with silver cyanate followed by reaction of the resulting isocyanates 5a,b with an appropriate alkoxyamine afforded N‐alkoxy‐N′‐[2‐alkyl‐3,3‐di(methylthio)acryloyl]ureas 6a,b in 85–88% yields. Cyclization of 6a,b in acetic acid containing methanesulfonic acid followed by oxidation with 3‐chloroperoxybenzoic acid gave high yields of 1‐alkoxy‐5‐alkyl‐6‐(methylsulfonyl)uracils 9a,b. Nucleophillic addition‐elimination reaction of 9a,b with sodium azide, phenylthiol, or phenylselenol produced 6‐azido‐1‐butoxythymine (2a, 98%), 5‐ethyl‐1‐(2‐phenoxyethoxy)‐6‐(phenylthio)uracil (2b, 95%), or 5‐ethyl‐1‐(2‐phenoxyethoxy)‐6‐(phenylselenenyl)uracil (2c, 91%).
Antimalarials: Synthesis of 4‐aminoquinolines that circumvent drug resistance in malaria parasites
Authors: De Dibyendu , Byers Larry D. , Krogstad Donald J.
Published: April 2009

The strategies described here have permitted the synthesis of a series of 4‐aminoquinoline antimalarials. Substantive improvements over previous syntheses include nucleophilic substitution with neat amine rather than in phenol, regioselective reductive alkylation to convert the terminal primary amine (12a–20a) on the diaminoalkane side chain to a diethylamino group, and purification by column chromatography with basic alumina. The 1H nmr spectra obtained after regioselective reductive alkylation with sodium borodeuteride (in comparison with sodium borohydride) demonstrated that this reductive alkylation proceeds via formation and subsequent reduction of the corresponding diamides in situ.
Selective, one‐pot synthesis of 2,3,6‐trisubstituted pyridine and 2‐cyclohexen‐1‐one derivatives from bicyclic ketals
Authors: Jun Jong‐Gab , Ha Tae Hee
Published: April 2009

Boron difluoromethanesulfonate, prepared from 5 equivalents of trimethylsilyl methanesulfonate and 1 equivalent of boron trifluoride etherate, has proved to be an active Lewis acid catalyst for the one‐pot transformation reaction of bicyclic ketals in the 6,8‐dioxabicyclo[3.2.1]octane series to 2,3,6‐trisubstituted pyridine or 2‐cyclohexen‐1‐one selectively, depending on conditions. A 1,5‐diketone was the reaction intermediate for both products. Pyridine was formed selectively by using a nitrile as a solvent or a reagent, but cyclohexenone was prepared in methylene chloride instead of a nitrile.
Base promoted transformation on thiadiazolopyridinium chlorides
Authors: Martinez Ana , Castro Ana , Fayet J. P.
Published: April 2009

1,2,4‐Thiadiazolo[2,3‐a]pyridinium chlorides undergo a very facile base promoted transformation to give bispyridilimino‐1,2,4‐thiadiazolidines. The unequivocal structural assignment of these last compounds was achieved by spectroscopic 1H, 13C and 15N two dimensional methods.
Site selectivity in the reaction of 2‐formyl‐2H‐azirine‐N‐arylimines with diphenylketene
Authors: Nunes José , Kascheres Albert
Published: April 2009

2‐Formyl‐2H‐azirine‐N‐arylimines 1a‐c react with diphenylketene 2 to afford 2H‐2‐azirinyl‐2‐azetidi‐nones 3a‐c and N‐aryldiphenylacetamides 4a‐c by reaction at the exo‐imine group. Derivatives containing the bulkier methyl group at the 2‐position, 1d‐f, produce only 4a‐c.
6‐Substituted thioquinanthrenes. Reaction of thioquinanthrene with radicals formed from DMF
Authors: Maślankiewicz Andrzej , Michalik Ewa
Published: April 2009

Reaction of bis‐hydrogen sulfate of thioquinanthrene with DMF‐ferrous sulfate‐hydroxylamine‐O‐sulfonic acid system took place at the α‐quinolinyl position and led to 6‐monosubstituted thioquinanthrene derivatives 1 (42%) and 2 (11%).
A new synthetic route to 2‐substituted naphtho[2,3‐b]furan‐4,9‐dione2‐Substituted Naphtho[2,3‐b]furan‐4,9‐dione
Authors: Koyanagi Jyunichi , Yamamoto Katsumi , Nakayama Kouji , Tanaka Akira
Published: April 2009

4,9‐Dimethoxynaphtho[2,3‐b]furan 9 was obtained in 91% yield via the reductive methylation of naphtho[2,3‐b]furan‐4,9‐dione 2. After treatment of 9 with butyllithium, the mixture was allowed to react with N,N‐dimethylacetamide, followed by oxidization with cerium(IV) diammonium nitrate to give 2‐acetylnaphtho[2,3‐b]furan‐4,9‐dione 1. 2‐Formylnaphtho[2,3‐b]furan‐4,9‐dione 13 and 2‐trimethylsilyl‐naphtho[2,3‐b]furan‐4,9‐dione 14 were also obtained from 9 by a similar method. The halodesilylations of 14 easily gave 2‐iodonaphtho[2,3‐b]furan‐4,9‐dione 16, 2‐bromonaphtho[2,3‐b]furan‐4,9‐dione 17, and 2‐chloronaphtho[2,3‐b]furan‐4,9‐dione 18 in 82%, and 93% and 83% yield, respectively. Furthermore, the nitrodesilylation of 14 gave 2‐nitronaphtho[2,3‐b]furan‐4,9‐dione 3 in 77% yield.
Reaction of 4‐hydroxy‐5‐oximino‐3‐thiophenecarboxylates with hydrazines. Formation of pyrazolylthiohydroxamic acids
Authors: Robey R. L. , Alt C. A. , Van Meter E. E.
Published: April 2009

The reactions of 4‐hydroxy‐5‐oximino‐3‐thiophenecarboxylates with hydrazine and substituted hydrazines have been investigated. The products of the reactions have been shown to be pyrazole‐3‐ or 5‐thiohydroxamic acids rather than the hydrazones previously described by Benary and Silberstrom. Two alternate mechanisms are proposed which account for the regiochemical outcome. The structures of the pyrazole‐3‐ and 5‐thiohydroxamic acids and corresponding nitriles have been proven by independent synthesis, comparison to known compounds, and by proton and carbon magnetic resonance and long range HETCOR experiments.
Reaction of 5‐substituted‐2‐amino‐2‐oxazolines with ethoxycarbonyl isocyanate. A route to 2,3,6,7‐tetrahydro‐4H‐oxazolo[3,2‐a]‐1,3,5‐triazine‐2,4‐diones
Authors: Adetchessi Ouro , Desor Daniel , Forfar Isabelle , Jarry Christian , Leger Jean Michel , Laguerre Michel , Carpy Alain
Published: April 2009

The reaction of 2‐amino‐2‐oxazolines with ethoxycarbonyl isocyanate was investigated in order to access to fused 1,3,5‐triazine‐2,4‐diones with a potential 5‐HT2 antagonist activity. The reaction leads to 2,3,6,7‐tetrahydro‐4H‐oxazolo[3,2‐a]‐1,3,5‐triazine‐2,4‐diones and to 1‐carbethoxy‐3‐(2‐iminooxazolidine)ureas. During the carbamoylation the regioselectivity seems to be related to the strong nucleophilic character of the endo nitrogen atom of 2‐amino‐2‐oxazolines. The structures of two compounds were studied by X‐ray crystallography. N‐Substituted compounds have been prepared by alkylation of the 2,3,6,7‐tetrahydro‐7‐phenoxymethyl‐4H‐oxazolo[3,2‐a]‐1,3,5‐triazine‐2,4‐dione.
Mass spectrometry of 3‐oxothiazolo[3,2‐a] and [3,2‐c]pyrimidin‐5‐ones. Correlation of the intensities of the M+. and the selected fragment ions
Authors: Wybieralska Jadwiga
Published: April 2009

The mass spectral fragmentation of eight new 3‐oxothiazolo[3,2‐a] and [3,2‐c]pyrimidin‐5‐ones were investigated. Fragmentation pathways are proposed on the basis of accurate mass and metastable transition measurements. The correlation between the intensities of M+. and the selected fragment ions of these compounds is discussed. The data obtained created the basis for distinguishing isomers and metamers.
Pyrrolo[2,1‐c][1,4]benzodiazepines. Synthesis of new cyclic amidines and fused[a]triazolo, tetrazolo and oxadiazolo derivatives
Authors: Gillard Alain‐Claude , Foloppe Marie‐Paule , Rault Sylvain
Published: April 2009

We report the practical synthesis of new cyclic amidines from thiolactams and the preparation of fused[a]triazolo, tetrazolo and oxadiazolo derivatives via hydrazidines and oximes, in the pyrrolo[2,1‐c]‐[1,4]benzodiazepine series.
Unexpected formation of benzaldehydes by the reactions of dithioacetals derived from cinnamaldehydes with 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone in aqueous solvents
Authors: Tanemura Kiyoshi , Nishida Yoko , Suzuki Tsuneo , Satsumabayashi Koko , Horaguchi Takaaki
Published: April 2009

1,3‐Dithianes 1, 1,3‐dithiolanes 2, and diphenyl dithioacetals 3 derived from cinnamaldehydes reacted with 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone in aqueous solvents to give benzaldehydes 4. Hydride transfer from 1–3 to 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone followed by hydrolysis and oxidative carbon‐carbon bond cleavage would produce benzaldehydes 4.
The nucleophilic ring‐opening of N‐benzylquinuclidinium bromide
Authors: Axelsson Oskar , Peters Dan
Published: April 2009

N‐Benzylquinuclidinium bromide was ring opened by a series of heteronucleophiles, in the presence of cesium carbonate, to yield the corresponding N‐benzyl‐4‐(2‐hetero‐ethyl)piperidines. The best yields were found with thiophenol (56%), phenol (55%), and benzimidazole (38%) as nucleophiles.
Synthesis of 11‐aminodibenzo[b,f][1,4]thiazepines and fluoro derivatives
Authors: Mettey Yvette , Lehuede Jacques , Vierfond Jean‐Michel
Published: April 2009

The reaction of balogenobenzonitriles with 2‐aminobenzenethiol is a new route, in a “one‐pot” or two‐step approach, to 11‐aminodibenzo[b,f][1,4]thiazepine and fluoro derivatives.
Synthesis of 1,2,4‐triazole and thiazole analogs of ketoconazole
Authors: Huang Liang‐Fu , Kim Jang‐Woo , Bauer Ludwig , Doss George
Published: April 2009

The synthesis of 1,2,4‐triazole and thiazole analogs of ketoconazole is described in which one of the α azole ring carbons is linked to C‐2 of the ketal by means of a three methylene tether. Lithiation of 1‐methyl‐1,2,4‐triazole and thiazole and subsequent alkylation with 2‐(2,4‐dichlorophenyl)‐2‐(3‐iodopropyl)‐1,3‐dioxolane produced, after an aqueous acidic workup, 2,4‐dichlorophenyl 3‐[5‐(1‐methyl‐1,2,4‐triazolyl) and 2‐thiazolyl]propyl ketones, respectively. Ketalization with glycerol furnished the corresponding diastereomeric pairs of cis and trans 1,3‐ dioxolanes. The reaction of 2,4‐dichlorophenyl 3‐[5‐(1‐methyl‐1,2,4‐triazolyl)]propyl ketone with 3‐mercapto‐1,2‐propanediol produced the corresponding diastereomeric cis and trans hydroxymethyl 1,3‐oxathiolanes. The diastereomeric racemates were separated by column chromatography and their stereochemistry established by nOe nmr experiments. Some of these racemic cis ketal alcohols were converted by benzyl bromide to the corresponding benzyl ethers. Several of these racemic cis‐ketals were reacted, first with methanesulfonyl chloride, then with 1‐acetyl‐4‐(4‐hydroxyphenyl)piperazine, to furnish the title compounds.
Convenient synthesis of 6‐substituted‐2‐chloro‐5,12‐dihydro‐5‐oxobenzoxazolo[3,2‐a]quinolines and N‐acylated‐3‐chlorodibenz[b,e][1,4]oxazepin‐11(5H)‐ones
Authors: Chung Sang J. , Joo Keum Chan , Kim Dong H.
Published: April 2009

Convenient synthesis of variously substituted 2‐chloro‐5,12‐dihydro‐5‐oxobenzoxazolo[3,2‐a]quinolines at the 6‐position and N‐acylated‐3‐chlorodibenz[b,e][1,4]oxazepin‐11(5H)‐ones are reported. The former compounds were obtained in 65–93% yield by simply heating N‐acyl‐4‐chloro‐N‐(2‐hydroxyphenyl)‐anthranilic acids in acetic anhydride for 4 hours, and the latter by heating sodium salt of N‐acyl‐4‐chloro‐N‐(2‐hydroxyphenyl)anthranilic acids with acetic anhydride.
Furopyridines. XXI. Synthesis of cyano derivatives of furo‐[2,3‐b]‐, ‐[2,3‐c]‐ and ‐[3,2‐c]pyridine and their conversion to derivatives having another carbon‐substituent
Authors: Shiotani Shunsaku , Taniguchi Katsunori
Published: April 2009

Cyanation of furo[2,3‐b]‐, ‐[2,3‐c]‐ and ‐[3,2‐c]pyridine N‐oxides 1a, 1b and 1c by the Reissert‐Henze method, reaction with benzoyl chloride and trimethylsilyl cyanide in dichloromethane and the reaction with trimethylsilyl cyanide and triethylamine in acetonitrile afforded 6‐cyanofuro[2,3‐b]‐ 2a, 7‐cyanofuro[2,3‐c]‐ 2b and 4‐cyanofuro[3,2‐c]pyridine 2c in moderate to excellent yield. The cyano group in 2a, 2b and 2c was converted to carboxamides 3a, 3b and 3c, ethyl imidates 5a, 5b and 5c and ethyl carboxylates 6a, 6b and 6c. Reaction of the N‐oxides with trimethylsily bromide in acetonitrile gave the deoxygenated furopyridine 7a and 7d, bifuropyridyl 8b and 8c, and the N‐oxide 9 of 8c.
Retro‐ene reactions in heterocyclic synthesis, III. A new route to 4,5‐dihydrooxazoles and 5,6‐dihydro‐4H‐1,3‐oxazines
Authors: Ito Kunio , Miyajima Shingo
Published: April 2009

Methyl (E)‐4,4‐dimethyl‐5‐oxo‐2‐pentenoate (1, X = O) reacted with 1,2‐ or 1,3‐aminoalcohols 3 to yield oxazolidines 4a‐c or tetrahydro‐1,3‐oxazines 4d,e. The corresponding imino ester 1 (X = NBu‐t) also gave 4 on reaction with 3. Compounds 4 on heating at 230° yielded 4,5‐dihydrooxazoles 5a‐c or 5,6‐dihydro‐4H‐1,3‐oxazines 5d,e along with methyl 4‐methyl‐3‐pentenoate (6).
Haloacetylated enol ethers. 8 [12]. Reaction of β‐alkoxyvinyl trihalomethyl ketones with guanidine hydrochloride. Synthesis of 4‐trihalomethyl‐2‐aminopyrimidines
Authors: Zanatta Nilo , Cortelini Maria de F. M. , Carpes Marcos J. S. , Bonacorso Helio G. , Martins Marcos A. P.
Published: April 2009

In this work the results of the reaction of β‐alkoxyvinyl trihalomethyl ketones 1, 2a‐e, with guanidine hydrochloride are reported. Depending on the ketone 1 or 2 and the conditions under which the reactions were carried out, 4‐trihalomethyl‐2‐amino pyrimidines, β‐alkoxyvinyl carboxylic acids, or β‐acetal carboxylic esters were obtained.
Facile and convenient synthesis of 2,6‐disubstituted 4H‐1,3‐oxazin‐4‐one derivatives
Authors: Morita Yasuo , Kaneko Masakazu , Matsuzawa Sumiko , Yamamoto Yutaka
Published: April 2009

Facile and convenient methods for the preparation of a variety of 2,6‐disubstituted 4H‐1,3‐oxazin‐4‐ones 3 by three complementary methods are described. Treatment of the branched aliphatic imidate 2c,d with diketene 1 in the presence of a catalytic amount of acetic acid affords 2‐substituted 6‐methyl‐1,3‐oxazin‐4‐ones 3c,d, whereas the unbranched imidate 2b,e gave oxazines 3b,e and pyrimidines 4b,e (Method A). The reaction of acyl Meldrum's acid 5 with imidate 2 afford 2,6‐disubstituted oxazine 3, though the alkylimidate with acetyl Meldrum's acid yielded 3 and 5‐acetyl‐1,3‐oxazine‐4,6‐dione 8 (Method B). The cylodehydration of acylacetylcarboxamide 13 with acid, such as 70% perchloric acid or fluorosulfonic acid, afforded 1,3‐oxazines 3 (Method C).
Synthesis of pyrido[2,3‐d]pyrimidinones by the reaction of aminopyrimidin‐4‐ones with benzylidene meldrum's acid derivatives
Authors: Quiroga Jairo , Hormaza Angelina , Insuasty Braulio , Nogueras Manuel , Sánchez Adolfo , Hanold Norbert , Meier Herbert
Published: April 2009

A series of pyrido[2,3‐d]pyrimidine‐4,7‐diones 5a‐h were prepared from 6‐amino‐4‐pyrimidones 1 and benzylidene Meldrum's acid derivatives 2 by cyclization reactions in boiling nitrobenzene. The structure of 5, determined by nmr measurements, reveals a selective orientation of 1 and 2 in the addition step.
Synthesis of halosulfuron‐methyl via selective chlorination at 3‐ and/or 5‐position of pyrazole‐4‐carboxylates
Authors: Morimoto Katsushi , Sato Toshiaki , Yamamoto Susumu , Takeuchi Hiroshi
Published: April 2009

Reactions of methyl pyrazole‐4‐carboxylates 4b‐d with N‐chlorosuccinimide under heating conditions without a solvent gave methyl 3,5‐dichloro‐1‐methylpyrazole‐4‐carboxylate 4a in good yields. The reaction of 4a with sodium hydrosulfide led to a nucleophilic substitution on the 5‐position regioselectively to afford methyl 3‐chloro‐1‐methyl‐5‐mercaptopyrazole‐4‐carboxylate 6a, which was followed by oxidative chlorination and amination to obtain 3‐chloro‐1‐methyl‐5‐sulfamoylpyrazole‐4‐carboxylate 2a. Finally, the reaction of 2a with phenyl 4,6‐dimethoxypyrimidin‐2‐yl carbamate 7 provided methyl 3‐chloro‐5‐(4,6‐dimethoxypyrimidin‐2‐ylcarbamoylsulfamoyl)‐1‐methylpyrazole‐4‐carboxylate (halosulfuron‐methyl) 1a promising herbicide in com.
Synthesis and metalation of trifluoromethylpyrimidines. Metalation of diazines. XVI
Authors: Plé N. , Turck A. , Heynderickx A. , Quéguiner G.
Published: April 2009

A new route to trifluoromethylpyrimidines is described. Lithiation of trifluoromethylpyrimidines was successfully achieved and was used to synthesize new pyrimidine derivatives. A new synthetic route to a biologically active molecule with antimycotic activities is reported.
A novel synthesis of 3‐halo‐2‐phenylquinoline‐4‐carboxylic acids
Authors: Raveglia Luca F. , Giardina Giuseppe A. M. , Grugni Mario , Rigolio Roberto , Farina Carlo
Published: April 2009

The 3‐chloro and 3‐bromo‐2‐phenylquinoline‐4‐carboxylic acids were obtained in good yields through a novel procedure, entailing the synthesis of the 3‐amino intermediate and the subsequent replacement of the amino group with chlorine or bromine, according to the Sandmeyer reaction.
Friedel‐crafts reactions of 2‐amino‐4‐(alkyl or aryl)oxazoles with acid chlorides and acid anhydrides: Synthesis of 5‐acyl‐2‐amino‐4‐alkyloxazoles
Authors: Mekonnen Belew , Crank George
Published: April 2009

Acid chlorides and anhydrides react with 2‐amino‐4‐alkyloxazoles in the presence of aluminum chloride to produce 5‐acyl substituted 2‐amino‐4‐alkyloxazoles in modest yields. However, in the absence of the Lewis acid reaction occurs at the amino group to give the corresponding amides. This provides a viable entry for functionalising and making carbon‐carbon bond at C‐5 of this heterocyclic system.
A new and facile synthesis of imidazo[2,1‐b]oxazoles
Authors: Mekonnen Belew , Crank George , Craig Donald
Published: April 2009

An efficient and clean two step procedure for the synthesis of imidazo[2,1‐b]oxazoles has been developed from 2‐aminooxazoles using titanium(IV) chloride assisted cyclization, and a variety of imidazo[2,1‐b]oxazoles have been synthesized in good yields. The structure of one of the products was confirmed by X‐ray crystallographic analysis.
Multiple 1,2,3‐thiadiazoles
Authors: Al‐Smadi Mousa , Hanold Norbert , Meier Herbert
Published: April 2009

A series of compounds 3a‐d,i‐n with two or three 1,2,3‐thiadiazole rings, useful for photocrosslinking processes, was prepared from the di‐ or triketones 1a‐d,i‐n via the corresponding hydrazones 2a‐d,i‐n by applying the Hurd‐Mori method. A special synthetic sequence, 1e, 2e, 3e, 3f/3g, was elaborated for the olefinic system 3h.
Stereoselective synthesis of cyclic ether compounds via reductive cleavage of bicyclic ketals
Authors: Jun Jong‐Gab
Published: April 2009

Bicyclic ketals in the 6,8‐dioxabicyclo[3.2.1]octane system readily reacted with triethylsilane‐boron tri‐fluoride etherate at room temperature to give only the cis‐tetrahydropyranol derivatives via C5‐O6 bond cleavage. Three‐ and erythro‐alcohols were prepared selectively from the endo‐ and exo‐ketal, respectively. Dehydrated products also formed when the tertiary alcohol was involved under these reaction conditions. However, the cleavage reaction with aluminum hydride gave the trans‐tetrahydropyranol as the major product without dehydration.
On triazoles XXXVII.. The correct structure of the products formed from 1,2,4‐triazolethiones with α‐halogenated acetophenones
Authors: Reiter József , Kajtár‐Peredy Mária , Bauer Ludwig
Published: April 2009

The reaction of 1,2,4‐triazolethiones with α‐halogenated acetophenones was re‐investigated. It was proven that in contrast to the literature data the products obtained were S‐alklylated derivatives.
Diastereoselective michael addition of nitrogen and sulfur‐nucleophiles to α,β‐unsaturated δ‐thiolactams
Authors: Sośnicki Jacek G. , Jagodziński Tadeusz S. , Liebscher Jürgen
Published: April 2009

5,6‐Dihydropyridine‐2‐thiones 2 are synthesized from 5,6‐dihydropyridin‐2‐ones 1 and Lawesson reagent. Stereoselective Michael‐like addition of amines, methylhydrazine or functionalized thiols affords trans piperidine‐2‐thiones 5 with the corresponding heterosubstituent in position 4 as major products. The configuration of the adducts 5 was determined by nmr‐techniques.
Syntheses and spectral properties of 2,3,7,8‐tetracyano‐5,10‐dihydrodipyrazino[2,3‐b:2′,3′‐e]pyrazine
Authors: Jaung Jae‐Yun , Fukunishi Koushi , Matsuoka Masaru
Published: April 2009

Base catalized intermolecular cyclization of 2‐amino‐3‐chloro‐5,6‐dicyanopyrazines gave 5,10‐disubsti‐tuted‐2,3,7,8‐tetracyano‐5,10‐dihydrodipyrazino[2,3‐b:2′,3′‐c]pyrazines 11–20. These compounds have rather small molecular size but have strong intramolecular charge‐transfer chromophoric system. They have strong fluorescence in solution and some have fluorescence even in the solid state which are very important to evaluate their electroluminescence property as an emitter for electroluminescence devices. The physical, structural, and electronic properties of these new 2,3,7,8‐tetracyano‐5,10‐dihy‐drodipyrazino[2,3‐b:2′3′‐e]pyrazines were studied using uv‐visible spectroscopy and the Pariser‐Parr‐Pople molecular orbital calculation method.
Semi‐synthesis of paclitaxel from naturally occurring glycosidic precursors
Authors: Rao Koppaka V.
Published: April 2009

Paclitaxel, an antitumor drug effective on ovarian and breast carcinomas, is currently being produced both by direct isolation from the bark of Taxus brevifolia and by semi‐synthesis from a natural precursor, 10‐deacetyl baccatin III. Although other potential precursors such as 10‐deacetyl paclitaxel‐7‐xyloside were known since 1984, their conversion to paclitaxel could not be achieved because of the lack of suitable methodology for hydrolyzing the xylose residue, compatible with the stability of the compound. A method is described here using periodate, followed by phenylhydrazine, to effect deglycosidation of 10‐deacetyl paclitaxel‐7‐xyloside to form 10‐deacetyl paclitaxel. In addition, by including an intermediate acetylation step before the reaction with phenylhydrazine, “direct” conversion of this xyloside to paclitaxel itself, is described. Because 10‐deacetyl paclitaxel‐7‐xyloside occurs at >0.1% in the bark of Taxus brevifolia, its successful hydrolytic conversion to paclitaxel represents an extremely important reaction for the enhanced availability of this drug.
A convenient synthesis of 1,3‐oxazolidin‐4‐ones and 1,3‐oxazin‐4‐ones
Authors: Wanner Klaus Th. , Weber Ulrich
Published: April 2009

1,3‐Oxazolidin‐4‐ones and 1,3‐oxazin‐4‐ones were synthesized by formal cyclocondensation of imines with α‐ or β‐hydroxy acids.
Hydrogen‐deuterium exchange in dimethylpyridines
Authors: Kebede Naod , Pavlik James W.
Published: April 2009

Dimethylpyridines undergo deuterium‐hydrogen exchange when heated in deuterium oxide containing potassium carbonate at ring positions 2 and 6 when these positions are unsubstituted and at methyl groups located at ring positions 2,4, and 6 exclusively.
Preparation of thiapyrimidinophanes from 2,4‐dithiouracil
Authors: Itahara Tosbio
Published: April 2009

Treatment of 2,4‐dithiouracil with dihaloalkanes under a basic condition gave three types of thiapyrim‐idinophanes, whose structures were confirmed by their nmr and mass spectral data.
A facile synthesis of the lowest homologues of meso‐tetraalkylporphyrin
Authors: Neya Saburo , Funasaki Noriaki
Published: April 2009

Utilization of a less stoichiometric amount of aldehyde in portions and addition of water to the reaction mixture depressed the tar formation, affording much easier isolation of meso‐tetraalkylporphyrins. The title porphyrins bearing methyl, ethyl, or n‐propyl substituents were synthesized in isolated yields of 10,10, and 8%, respectively.
meta‐Benzenotetratetrazolophanes
Authors: Butler Richard N. , Fleming Adrienne F. M.
Published: April 2009

A route to meta‐benzenocyclophanes containing four tetrazole rings in the macrocycle is described.
Long‐range 1H‐15N two‐dimensional heteronuclear shift correlation of the alkaloid vincamine at natural abundance
Authors: Martin Gary E.
Published: April 2009

Long‐range 1H‐15N heteronuclear correlation pathways in the alkaloid vincamine, a structural constituent or biogenetic congener of numerous Vinca alkaloids, are reported. Correlations were observed through the use of the GHNMQC (Gradient‐enhanced Hydrogen‐Nitrogen Multiple Quantum Coherence) 2D nmr experiment at natural abundance. An unanticipated four‐bond coupling between the H15a resonance and N4 was observed in contrast to the typical two‐ and three‐bond coupling pathways. Nitrogen‐15 chemical shift comparisons are drawn between vincamine and structurally related alkaloids including ajmaline and the velbanamine portion of the semi‐synthetic alkaloid vinorelbine (NavelbineTM).
A novel route to 1‐benzyl‐1,2,4‐triazole derivatives through disproportionation of isothiosemicarbazones
Authors: Yamazaki Chiji , Ohno Mariko
Published: April 2009

Aromatic isothiosemicarbazones 1–4 underwent disproportionation at elevated temperature in the presence of a thiol or a thiol‐releasing substance to give 1‐arylmethylene‐3‐alkylthio‐5‐aryl‐1H‐1,2,4‐triazole derivatives 6–9 in moderate yields. An isothiosemicarbazone of aliphatic aldehyde with no α‐hydrogen did not give rise to the corresponding disproportionation under the similar conditions. Cross reaction occurred between two different isothiosemicarbazones but the cross compound could be isolated only in a poor yield. Any inert solvent markedly inhibited the disproportionation reaction even only with a slight dilution. A tentative reaction mechanism, in which it might involve a potential nitrene‐sulfonium ion pair as a key step, is presented.
Synthesis of 6‐cyanopurines and the isolation and X‐ray structure of novel 2H‐pyrroles
Authors: Alves M. José , Carvalho M. Alice , Proença M. Fernanda J.R.P. , Booth Brian L. , Pritchard Robin G.
Published: April 2009

(Z)‐N1‐(2‐Amino‐1,2‐dicyanovinyl)‐N2‐substituted‐formainidines react with dimethylformamide diethyl acetal at room temperature to give 6‐cyanopurines as the major product together with novel 5‐amino‐2‐arylimino‐3,4‐di[(N,N‐dimethylamino)methylideneamino]‐2H‐pyrroles, which have been fully characterised and a single crystal X‐ray analysis has been carried out on the N‐phenyl derivative.
Synthesis and spectral properties of methyl 5‐[(o‐, m‐, and p‐R)‐phenoxy]‐2‐benzimidazolecarbamate
Authors: Cortés Eduardo Cortés , Anaya Luis Angel Araluce
Published: April 2009

The preparation of eleven novel methyl 5‐[(o‐, m‐, p‐R)‐phenoxy‐2‐benzimidazolecarbamates with possible pharmacological activity as anthelmintics is described. The structure of all products was corroborated by ir, 1H‐nmr, 13C‐nmr and mass spectra.
Synthesis and aggregation of cationic porphyrins
Authors: Dancil Keiki‐Pua S. , Hilario Lynn F. , Khoury Richard G. , Mai Kim U. , Nguyen Chi K. , Weddle Katherine S. , Shachter Amy M.
Published: April 2009

Tetra(N‐R‐pyridinium‐4‐yl)porphyrin and tetra(N‐R‐pyridinium‐3‐yl)porphyrin derivatives were synthesized with R = 3, 6, and 8 carbon alkene, alcohol and carboxylic acid chains. Self‐aggregation of these systems was studied at I = 0.1 using visible spectroscopy. N‐Alkyl chain length and functionality were determined to play the dominant role in aggregation of the cationic porphyrins. Position of peripheral charge (meta vs. para) also influenced spectral changes and the nature of the aggregate.
A cyclopropenone route to new pyrrolizidine derivatives
Authors: Kascheres Albert , Schumacher Heloisa C. , Rodrigues Reinaldo A. F.
Published: April 2009

New pyrrolizidine derivatives 6 and 7 were prepared from the 1, 5‐dihydro‐2H‐pyrrol‐2‐one 3a via an acidic intramolecular aldol condensation in 16% and 42% yields, respectively. Compound 6 was obtained by dehydration of 7 with p‐toluenessulfonic acid in 67% yield.
Ring transformation of 5‐amino (or acylamino)‐6‐hydroxy (or benzoyloxy)methylpyrimidin‐4(3H)‐ones into 1H‐imidazoles
Authors: Ueda Taisei , Asai Satoko , Oiji Khoji , Nagai Shin‐Ichi , Nagatsu Akito , Sakakibara Jinsaku
Published: April 2009

Treatment of 5‐acylamino‐6‐hydroxy (or benzoyloxy)methyl‐3‐phenylpyrimidin‐4(3H)‐one 5,10 with 5% aqueous sodium hydroxide in ethanol gave 2‐alkyl‐5‐hydroxymethyl‐4‐phenylcarbamoyl‐1H‐imidazoles 7,11. Oxidation of 5‐amino‐6‐benzoyloxymethyl‐3‐phenylpyrimidin‐4(3H)‐one 9 in the presence of copper(II) chloride in alcohol gave 2‐alkoxy‐5‐alkoxymethyl‐4‐phenylcarbamoyl‐1H‐imidazoles 12a,b accompanied by 5‐amino‐6‐alkoxymethyl‐3‐phenylpyrimidin‐4(3H)‐ones 13a,b.
Synthesis of new type benzo[b]thiophene fused quinones and their tetracyanoquinodimethane derivatives
Authors: Ohba Yoshihiro , Murakami Yasuo , Sone Tyo , Awano Hiroshi
Published: April 2009

A series of new type of benzo[b]thiophene‐fused 1,4‐benzoquinones and their tetracyanoquinodimethane derivatives were synthesized. The cyclic voltammetric data of new type quinones and tetracyanoquinodimethane derivatives displayed different behavior. All new quinones exhibit two reduction waves corresponding to the radical anion and dianion. On the other hand, most tetracyanoquinodimethane derivatives display a singlewave reduction to the dianion. The benzo[b]thiophene moiety fused tetracyanoquinodimethane derivatives reveal more negative reduction potentials than that of tetracyanoquinodimethane.
Thermolysis of N‐allylic 1,2,4‐triazoles
Authors: Carlsen Per H. J. , Jørgensen Kåre B.
Published: April 2009

A number of 4‐allylic substituted 3,5‐diphenyl‐4H‐1,2,4‐triazoles were thermolyzed at 315–320° in evacuated glass ampoules. The main reaction in the melt was rearrangement to the corresponding 1‐substituted triazoles, which appeared to proceed via competing SN2 and SN2′ mechanisms. The allylic systems were observed to undergo [2,3]‐allyl walk reactions between the 1‐ and 2‐ring positions. Allyl to vinyl isomerization also took place. Substitution of the allylic moiety increased the rate of reaction but decreased the rate of isomerization of allylic to the vinylic substituted triazoles. The 4‐vinyl substituted triazoles were inert under the reaction conditions. Some triazoles were converted into substituted pyridines. This was proposed to proceed via nitrogen extrusion and formation of a 1,3‐dipolar intermediate (nitrile ylide) which added intramolecularly to the allyl moiety and subsequently aromatized to the pyridine.