Synthesis and 13C-NMR study of pyrazolo[4,5-c] and pyrazolo[4,3-c benzazepines. III

The synthesis of pyrazolo[4,5-c][1]benzazepin-10-ones 10 and 13 and pyrazolo[4,3-c][1]benzazepin-10-ones 11 and 12 is reported. The structure of compounds 10-13 and that of their parent compounds 2-5 ensues from a ¹³C nmr study.     

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 3. A new highly electron-deficient octacationic macrocycle: tetrakis-2,3-[5,6-di{2-(N-methyl)pyridiniumyl}pyrazino]porphyrazine, [(2-Mepy)8TPyzPzH(2)]8+

A new octacationic macrocycle, tetrakis-2,3-[5,6-di{2-(N-methyl)pyridiniumyl}pyrazino]porphyrazine, was obtained in its hydrated form as the water-soluble iodide salt. This compound, abbreviated as [(2-Mepy)(8)TPyzPzH(2)](I(8)).8H(2)O (2-Mepy = 2(N-methyl)pyridiniumyl moiety), was obtained by demetalation of the corresponding Mg(II) complex, [(2-Mepy)(8)TPyzPzMg(H(2)O)](I(8)).5H(2)O, which in turn was prepared from its corresponding neutral hydrated species tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato(monoaquo)magnesium(II), [Py(8)TPyzPzMg(H(2)O)].4H(2)O, by reaction with CH(3)I in N,N-dimethylformamide. The quaternization reactions by using CH(3)I or methyl p-toluenesulfonate were also conducted on the monomeric precursor 2,3-dicyano-5,6-di(2-pyridyl)-1,4-pyrazine, [(CN)(2)Py(2)Pyz], with formation of the monoquaternized ion [(CN)(2)Py(2-Mepy)Pyz](+) neutralized by iodide and p-toluenesulfonate anions. Single-crystal X-ray work allowed elucidation of the structure of the two salt-like species. The diquaternized ion [(CN)(2)(2-Mepy)(2)Pyz](2+) could also be obtained as a p-toluenesulfonate salt, but attempts at direct macrocyclization of this dicationic species were unsuccessful. The iodide salt [(2-Mepy)(8)TPyzPzH(2)](I(8)).8H(2)O is water-soluble, with different solubilities depending on the range of pH explored. It was established that the macrocycle [(2-Mepy)(8)TPyzPzH(2)](8+) undergoes facile deprotonation and behaves as a strong acid. Aggregation phenomena are observed for both the octacation [(2-Mepy)(8)TPyzPzH(2)](8+) and its corresponding centrally deprotonated species [(2-Mepy)(8)TPyzPz](6+). Nevertheless, both cationic moieties exist in their monomeric form under specific experimental conditions. UV-visible monitored titrations with NaOH provide information about the type of protonation/deprotonation equilibria which are complicated by the occurrence of aggregation phenomena.     

Esistenza e unicità per campi elettromagnetici stazionari con condizioni al contorno dissipative

Sunto Per un problema relativo allo studio di campi elettrici armonici con una condizione al contorno dissipativa espressa dalla relazione: (*) E^t=*H^t×n si perviene a un teorema di esistenza, unicità e dipendenza continua. Cioè si prova la correttezza del problema ehe invece non sussiste se si sostituisce la relazione (*) con la usuale condizione al contorno dei conduttori perfetti: E^t×n=0.

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Summary For the problem relating to the study of electromagnetic fields with a dissipative boundary condition expressed by the relation: (*) E^t=*H^t×n we prove a theorem of existence, uniqueness and continuous dependence. That is we prove the correctness of the problem that does not exist if we replace the relation (*) by the customary boundary condition for a perfect conducting medium: E^t×n=0.

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Lavoro eseguito nell'ambito delle attività del G.N.F.M.     

Cyclotrimerization of ‘Oxabenzonorbornadiene’: Synthesis of syn‐ and anti‐5,6,11,12,17,18‐Hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene

An efficient synthetic route to the concave‐shaped, potentially ionophoric syn‐ and anti‐isomers of 5,6,11,12,17,18‐hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene ( 4 ) was elaborated. Starting from ‘oxabenzonorbornadiene’ ( 5 ), the stannylated precursor 9 was prepared in three steps, followed by cyclotrimerization catalyzed by copper(I) thiophene‐2‐carboxylate (CuTC) , which afforded 4 in a syn/anti ratio of 5 : 4.     

Comparative modal analysis of NRD parallelepiped dielectric resonators

The resonance modes of dielectric resonators having parallelepiped shape are extensively investigated in this work referring to the nonradiative dielectric (NRD) topology. Different numerical techniques, both rigorous and approximated (boundary elements, point matching, finite elements, transmission line approaches), are proposed and implemented to compute the relevant resonance spectrum as a function of the involved geometric and electromagnetic parameters. The theoretical results are discussed and compared also in connection with experimental investigations, carried out on suitable prototypes of NRD components. Qualitative and quantitative information is thus achieved to characterize with accuracy and efficiency the basic parameters (resonant frequencies, field configurations, etc.) involved in filter design and in other applications at microwaves and millimeter waves.     

A short approach to chaetomellic anhydride A from 2,2-dichloropalmitic acid: elucidation of the mechanism governing the functional rearrangement of the chlorinated pyrrolidin-2-one intermediate

Chaetomellic anhydride A was efficiently attained in three steps, starting from 2,2-dichloropalmitic acid and 2-(3-chloro-2-propenylamino)pyridine. Atom transfer radical cyclisation selectively formed the cis-stereoisomer of the trichloropyrrolidin-2-one, which underwent a stereospecific functional rearrangement to form a substituted maleimide. The choice of 2-pyridyl, as ‘cyclisation auxiliary’ in the atom transfer radical cyclisation step, proved beneficial for hydrolysis of the maleimide to form the desired anhydride.