Franco Sannicolò

Chiral atropisomeric five-membered biheteroaromatic diphosphines: New ligands of the bibenzimidazole and biindole series

Abstract Two new chiral atropisomeric biheteroaromatic diphosphines are described: 2,2′-bis(diphenylphosphino)-1,1′-bibenzimidazole (3a) and 3,3′-dimethyl-1,1′-bis(diphenylphosphino)-2,2′-biindole (4a). Structural characterization is given and configurational stability at room temperature demonstrated. The oxidation potential was recognized as a good tool to evaluate the electronic availability of the phosphorus atom in the series of biheteroaromatic diphosphines. Its value increases parallel to the electronic demand of the heterocyclic system and also depends on the position of the diphenylphosphino group.

Gastrointestinal-sparing anti-inflammatory drugs: The development of nitric oxide-releasing NSAIDs

Nonsteroidal anti‐inflammatory drugs (NSAIDs) are among the most widely prescribed medications, but their use continues to be limited by significant toxicity, particularly in the gastrointestinal tract and kidney. Better understanding of the pathogenesis of these adverse effects has led to the development of a series of derivatives of standard NSAIDs that are not only less toxic but more efficacious. The coupling of a nitric oxide‐releasing moiety to a range of NSAIDs greatly reduces their ability to induce gastrointestinal damage, and greatly increases their tolerability in situations in which there is preexisting gastrointestinal inflammation. There is also evidence that these compounds are much better tolerated by the kidney. On the other hand, the analgesic and anti‐thrombotic properties of NO‐releasing NSAIDs significantly exceed those of the parent drugs. These compounds appear to represent a significant advance in the treatment of inflammation and pain and for prophylaxis of thrombotic conditions. Drug Dev. Res. 42:144–149, 1997.

(Diphenylphosphino)-biheteroaryls: the first example of a new class of chiral atropisomeric chelating diphosphine ligands for transition metal catalysed stereoselective reactions

Ruthenium(II) dichloride complexes with (+)- and (–)-2,2′-bis(diphenylphosphino)-4,4′,6,6′-tetramethyl-3,3′-bibenzo[b]thiophene (1a), new chiral atropisomeric heterocyclic ligands, reduce α- and β-oxoesters to α- and β-hydroxyesters with an enantiomeric purity comparable, if not higher, to that reported for binap under the same experimental conditions.

Intramolecular delocalization of Π electrons in polythiophenes with fixed conformation: A spectroscopic study

The main feature of β,β’‐bridge–α,α’‐bithienyls is that their conformation is controlled by the bridge length. This class of molecules could be useful for the understanding of the intra and intermolecular processes which determine the conductivity of the corresponding polymers. In this work we have recorded and studied (i) the electronic spectra of the monomers, (ii) the vibrational spectra (IR, Raman λexc=514 nm, FT–Raman λexc=1064 nm) of the monomers and polymers in the pristine state, (iii) the IR spectra of the doped polymers, and (iv) the IR spectra (probe) of the polymers photoinduced by visible light (pump). The interpretation of the spectra is made in terms of the ‘‘effective conjugation coordinate’’ theory. Poly(cyclopentabithiophene) P(T+1) has the largest π‐electron delocalization with a wide distribution of conjugation lengths. In poly(cycloheptabithiophene) P(T+3) π electrons are highly localized, while an intermediate situation is observed in poly(dihydrobenzobithiophene) P(T+2). The various aspects of intra and intermolecular hopping of charge carriers are discussed.The main feature of β,β’‐bridge–α,α’‐bithienyls is that their conformation is controlled by the bridge length. This class of molecules could be useful for the understanding of the intra and intermolecular processes which determine the conductivity of the corresponding polymers. In this work we have recorded and studied (i) the electronic spectra of the monomers, (ii) the vibrational spectra (IR, Raman λexc=514 nm, FT–Raman λexc=1064 nm) of the monomers and polymers in the pristine state, (iii) the IR spectra of the doped polymers, and (iv) the IR spectra (probe) of the polymers photoinduced by visible light (pump). The interpretation of the spectra is made in terms of the ‘‘effective conjugation coordinate’’ theory. Poly(cyclopentabithiophene) P(T+1) has the largest π‐electron delocalization with a wide distribution of conjugation lengths. In poly(cycloheptabithiophene) P(T+3) π electrons are highly localized, while an intermediate situation is observed in poly(dihydrobenzobithiophene) P(T+2). The various...

Calix[4]arene-functionalized poly-cyclopenta[2,1-b;3,4-b′]bithiophenes with good recognition ability and selectivity for small organic molecules for application in QCM-based sensors

Some C2v symmetric cyclopenta[2,1-b;3,4-b′]bithiophenes differently substituted at the 4 position with a calix[4]arene group were synthesized and electrochemically polymerized by anodic coupling. The polymers were characterized by cyclic voltammetry, UV-vis and FTIR spectroscopy. Quartz crystal microbalance analysis showed strong affinity and selectivity of the polymers for toluene and acetone from the gas phase. The absorption process associated with the calix unit was satisfactorily described through a Langmuir isotherm, while a very small linear contribution was given by the polythiophene backbone. The absorption capacity of these materials was found to be higher by a magnitude of three orders than those displayed by cyclopentabithiophene-based polymers devoid of the calix unit, thus supplying strong, though indirect, proof of the role played by the calix units in the absorption process.

Expeditious synthesis of dihydrobenzo-[2,1-b:3,4-b′]-,[1,2-b:5,4-b′], and [1,2-b : 4,5-b′]-dipyrroles

A simple, high-yield, two-step synthesis of the title compounds (1)–(3) is described, based on the catalytic reduction of the bis-enamines (4)–(6), in turn obtained by condensation of dimethylformamide diethyl acetal with the appropriate dinitro-xylene.

New synthetic routes to electroconductive polymers containing thiophene units

A novel entry to polymers containing thiophene units is presented, based on coupling of monomers bis-lithiated at the thiophene termini; iodine and AsF5-doping of the polymers to give electroconductive materials is described.

Effects of the electronic properties of chiral chelating diphosphines in stereoselective Diels–Alder cycloaddition reactions promoted by their transition metals complexes

Abstract The Pd(II) and Pt(II) complexes (perchlorates and hexafluoroantimoniates, respectively) of a series of C2 symmetric biheteroaromatic diphosphines differing in their electronic properties at phosphorus have been tested as catalysts in [4+2]-cycloaddition reactions of cyclopentadiene and N-2-alkenoyl-1,3-oxazolidine-2-ones. The best stereoselection results were obtained with the complexes produced from electron-rich ligands, which were found to give also the kinetically most active catalysts.

Fusion of heterocyclic polymerogenic units onto a central ring : a fruitful approach to the investigation and specific tailoring of the dependence of electrical properties on monomer structure in conductive polyheterocycles

Abstract In this review the ‘spacer’ strategy is described and evaluated in detail. According to this principle, the monomer contains, as terminal units, two polymerogenic rings (pyrrole or thiophene) linked to a central π-conjugatively-active frame; as spacers, we have investigated ethenylic, sulphide, and aromatic moieties. In this way the redox potentials, E 0 , of the polymers derived from such monomers can be calibrated by the substituent effect exerted by the spacer. This control is beneficial because it is possible to increase the E 0 value of polypyrrole-type systems and decrease the E 0 value of polythiophene-type systems. Also, the ‘spacer’ may be further functionalised and, being remote from the polymerisation site, cannot alter the conductivity characteristics typical of the polymer derived from the parent heterocycle (pyrrole or thiophene): such a functionalisation may provide the final, tailored, conductive polymer with special properties (e.g., solubility). If the central ring, acting as a ‘spacer’, is formed linking two positions of a di-heterocycle with a saturated chain, it is possible partially to control the twist angle between the heterocyclic units. Crystal and molecular structures have shown that dipyrrole units, further linked through the nitrogen atoms, are quite sensitive to the central ring size. With regard to the conductivity of unsubstituted polypyrrole, the conductivity of the polymers derived from such monomers is dependent upon the twist angle between the rings. This result is relevant to a description of conjugation conditions between the heterocyclic units of a monomer required to produce a conductive polymer on doping.

Studies on the Fischer indole synthesis: Behaviour of cyclic hydrazones of tetrahydropyridazine and pyrazoline series in polyphosphoric acid.

Abstract Heating 1,3-diphenyl-1,4,5,6-tetrahydropyridazine in PPA affords mainly 4-benzoyl-1,2,3,4-tetrahydroquinoline and 2-anilinopropiophenone. In analogous conditions 1,5-diphenyl-3-methyl-2-pyrazoline gives 2-styrylindole, benzidine and benzylideneacetone.