New ionic liquid crystal compounds having a 1,3-dithiane or 1,3-dioxane ring

New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-dithiane ring in the central core N-substituted 4-(5-alkyl-1,3-dithian-2-yl)pyridinium bromides and the corresponding 1,3-dioxanes were synthesized and their mesomorphic behaviours compared. The principal feature of these compounds is to exhibit a smectic A phase over a very wide temperature range including room temperature.     

Cyclization of chalcones to isoxazole and pyrazole derivatives

A series of pyrazole and isoxazole derivatives were obtained by the condensation of the chalcones with hydrazine, phenylhydrazine, and hydroxylamine. All compounds were characterized using NMR, IR, and MS techniques.     

Collision-induced dissociation of valdecoxib metabolites: a novel rearrangement involving an isoxazole ring

Valdecoxib is a potent COX-2 inhibitor. During metabolism studies of valdecoxib by liquid chromatography/tandem mass spectrometry, we observed a novel mass spectral rearrangement involving an isoxazole ring for some of the metabolites in the negative ion mode. Accurate mass measurements were performed with quadrupole time-of-flight mass spectrometry to determine the elemental compositions of the fragments. Additionally, two types of stable-isotope labeled analogues were prepared to assist with the assignments of these fragments and possible mechanistic rearrangements resulting from collision-induced dissociation (CID). Detailed analyses of the CID mass spectra suggest that the fragmentation process involves a novel two-step rearrangement. The first step consists of an intramolecular SN2 reaction with a five-membered ring rearrangement to form an intermediate. The second step involves a four-membered ring intramolecular rearrangement followed by a cleavage of the N-O bond on the isoxazole ring to form a unique fragment ion at m/z 196. The same phenomenon was observed for a group of structurally related metabolites that also contain a 5-hydroxymethyl or 5-carboxylic acid moieties. A mechanism for the novel rearrangement involving an isoxazole ring is proposed.     

Conversion of the quinoline ring to an indole ring

4-Nitro-3-hydroxyquinoline is readily converted to indole derivatives in aqueous alkaline and acetic acid media. The contraction of the quinoline ring to an indole ring under the conditions of mild methylation of 4-nitro-3-hydroxyquinoline in an aqueous alkaline medium proceeds through the formation of the N-methyl de rivative of 4-nitro-3-hydroxyquinoline and N-methyl-2-formyl-3-nitroindole. 3-Nitroindole is formed when 4-nitro-3-hydroxyquinoline is heated in aqueous alkali, whereas isatin is formed in acetic acid. The methylation of 4-nitro-3-hydroxyquinoline in refluxing acetic acid leads to N-methylisatin.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 513–516, April, 1979.     

Synthesis of 1,3-diazepines and ring contraction to cyanopyrroles

Several tetrazolo[1,5-a]pyridines/2-azidopyridines undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes, as well as ring cleavage to cyanovinylketenimines, in low temperature Ar matrices. 6,8-Dichlorotetrazolo[1,5-a]pyridine/2-azido-3,5-dichloropridine undergoes ready exchange of the chlorine in position 8 (3) with ROH/RONa. 8-Chloro-6-trifluoromethyltetrazolo[1,5-a]pyridine undergoes solvolysis of the CF(3) group to afford 8-chloro-6-methoxycarbonyltetrazolo[1,5-a]pyridine. Several tetrazolopyridines/2-azidopyridines afford 1H- or 5H-1,3-diazepines in good yields on photolysis in the presence of alcohols or amines. 5-Chlorotetrazolo[1,5-a]pyridines/2-azido-6-chloropyridines and undergo a rearrangement to 1H- and 3H-3-cyanopyrroles and, respectively. The mechanism of this rearrangement was investigated by (15)N-labelling and takes place via transient 1,3-diazepines. The structures of 6,8-dichloro-tetrazolo[1,5-a]pyridine, 6-chloro-8-ethoxytetrazolo[1,5-a]pyridine, dipyrrolylmethane, and 2-isopropoxy-4-dimethylamino-5H-1,3-diazepine were determined by X-ray crystallography. In the latter case, this represents the first reported X-ray crystal structure of a 5H-1,3-diazepine.     

Synthesis of macrocyclic compounds that are condensed with a pyrazole ring

2-Carbethoxy-[11]--cyclothien-1-one, 2-carbethoxycyclopentadecanone, and 2,15-dicarbethoxy-[9,9]--cyclodithiene-1,14-dione were converted to 2-phenyl-1-methyl-[11]--cyclothieno [1,2-d] pyrazol-3-one, 2-phenyl-1-methyl-4,5-tridecamethylenepyrazol-3-one, and 2,16-diphenyl-1, 15-dimethyl- [9,9]-, -cyclodithienobis [(1,2-d, 14,15-d) pyrazole]-3,17-dione, respectively, by condensation with phenylhydrazine and subsequent methylation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 920–923, July, 1980.     

Preparation and reactions of 3-phosphinyl-1-aza-1,3-butadienes. Synthesis of phosphorylated pyridine and pyrazole derivatives

3-Phosphinyl 1-aza-1,3-butadienes 2 are obtained by aldol condensation between hydrazonoalkyl phosphine oxides and N,N-dimethylformamide dimethyl acetal. Transamination reaction of these azadienes with amines yields functionalized 1-aza-1,3-butadienes 3. Cycloaddition processes of these azadienes 2a with electron-poor dienophiles to give phosphorylated pyridine derivatives 9 and 15 are also reported, while intramolecular cyclization reaction of heterodiene 2b affords phosphorylated pyrazole 17.     

Radical Truce-Smiles reactions on an isoxazole template: Scope and limitations

The use of TiCl₃-HCl as promotor in the radical Truce-Smiles reactions of 2-(((3,5-dimethylisoxazol-4-yl)sulfonyl)oxy)benzenediazonium salts has been investigated in detail. During these reactions the desired Truce-Smiles rearrangement (via an ipso-substitution reaction) is accompanied by the formation of a number of by-products including dihydrobenzo[5,6][1,2]oxathiino[3,4-d]isoxazole 4,4-dioxides, dioxidobenzo[e][1,2]oxathiin-3-yl)ethan-1-ones, anilines and chloroaromatics. Replacing TiCl₃-HCl by Cu(NO₃)₂-Cu₂O as reductant in these reactions was found to afford broadly comparable product distributions. Competition and radical clock experiments also provide an indication of the relative susceptibility of the isoxazole nucleus towards attack by aryl radicals.     

Photochromism of a diarylethene having an azulene ring

Diarylethene derivatives incorporating an azulene ring at the ethene moiety were synthesized. One derivative having thiazole rings showed the expected coloration reaction by excitation at 313 nm (to a higher singlet state) but not when excited at 635 nm (S(0) to S(1) excitation). The system demonstrates that the cyclization reaction can be controlled by selective excitation at different wavelengths of the absorption spectrum. On the other hand, another derivative having thiophene rings did not show any photochromism. The results clearly show the importance of the coplanarity of the system for the photoisomerization.     

Synthesis of new pyrazole and triazole derivatives containing a saturated γ-lactone ring

Russian Journal of Organic Chemistry -     

Preparation of pyrazole and isoxazole libraries on cellulose beads: a new cheap and versatile biopolymer

A cellulose-based resin has been used to prepare a library of pyrazoles and isoxazoles via in situ generation of a polymer-bound enaminone. The synthesis is more versatile and efficient than the methods that had been previously described. Treatment of cellulose-bound enaminone with hydroxylamine or phenylhydrazine afforded the corresponding isomerically pure target heterocycles in high yield directly in solution, restoring the starting cellulose. To cite this article: L. De Luca et al., C. R. Chimie 6 (2003).     

Synthesis of pyrazole,isoxazole, and pyrimidine derivatives from 2-arylsulfonyl-2-cyanovinyl ethyl ethers

1-Substituted 4-arylsulfonyl-5-aminopyrazoles were obtained by condensation of 2-arylsulfonyl-2-cyanovinyl ethyl ethers with hydrazine or its derivatives (phenylhydrazine and semicarbazide); condensation with hydroxylamine gave 4-arylsulfonyl-5-aminoisoxazoles, and condensation with thiourea gave 2-thioxo-4-amino-5-arylsulfonyl-1,2-dihydropyrimidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 969–971, July, 1978.     

Synthesis and reactions of heterodinuclear organopalladium complex having an unsymmetrical PN ligand

Novel heterodinuclear organopalladium complexes having an unsymmetrical PN ligand (Et₂NC₂H₄PPh₂-κ²N,P)RPd-ML_n (ML_n = Co(CO)₄; R = Me (2a), Ph (2b), ML_n = MoCp(CO)₃; R = Ph (3b)) are synthesized by metathetical reactions of PdRX(Et₂NC₂H₄PPh₂-κ²N,P) (X = I, NO₃) with Na⁺[ML_n]⁻. Reversible dissociation of the Pd-N bond in 3b is revealed by variable temperature NMR studies. Reactions of 2a and 2b with CO yield corresponding acyl complexes (Et₂NC₂H₄PPh₂-κ²N,P)(RCO)Pd-Co(CO)₄ (R = Me (5a), Ph (5b)). Rate of CO insertion for 2a and 2b is significantly faster than those for mononuclear methylpalladium complex, PdMeI(Et₂NC₂H₄PPh₂-κ²N,P) (1a), and methylpalladium-cobalt complex with a 1,2-bis(diphenylphosphino)ethane (dppe) ligand, (dppe-κ²P,P′)MePd-Co(CO)₄ (6a). 5a smoothly reacts with nucleophiles such as diethylamine, methanol and benzenethiol to give corresponding amide, ester and thioester, respectively. These reactions of 5a are also significantly faster than those of corresponding mononuclear analogues and the similar heterodinuclear complexes with symmetrical bidentate ligands such as 1,2-bis(diphenylphosphino)ethane or N,N,N′,N′-tetramethylethylenediamine ligand.     

Synthesis and bioactivity of novel pyrazole oxime derivatives containing oxazole ring

A series of novel pyrazole oxime derivatives containing oxazole ring were designed and synthesized. The title compounds were structurally confirmed by 1H NMR, 13C NMR spectra and elemental analyses. Preliminary bioassay results showed that some of the title compounds displayed promising fungicidal activity besides insecticidal and acaricidal activity. Particularly, compound 8c exhibited potent fungicidal activity against cucumber Pseudoperonospora cubensis beyond good insecticidal activity against Aphis craccivora and Nilaparvata lugens.     

Conversion from arenes having a benzene ring to those having a picolinic acid by simple growing cell reactions using Escherichia coli that expressed the six bacterial genes involved in biphenyl catabolism

The comprehensive bioconversion of aromatic compounds with a benzene ring to a picolinic acid was achieved with a recombinant Escherichia coli strain that expressed the six genes involved in biphenyl catabolism, these being the bphA1(2072)A2A3A4 genes encoding the evolved biphenyl dioxygenase, the bphB gene encoding dihydrodiol dehydrogenase, and the bphC gene encoding catechol 2,3-dioxygenase.