Licia Trimarco

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.

(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.

Rate enhancement of 1,3‐dipolar cycloaddition of N‐methylindole: the singular role of Grignard reagents

The reactions of 2-N-methylindolyl and 2- and 3-benzo[b]thiophenyl anions with nitrile oxides and nitrilimines were performed in order to investigate whether the use of anionic dipolarophiles modifies a classical 1,3-dipolar cycloaddition. When lithium compounds were used as bases, the heterocyclic anions invariably acted as nucleophilic species; in contrast, when a Grignard reagent was employed, the N-methylindole gave cycloaddition products with an extraordinary rate enhancement. The hypothesis that N-methylindole and ethylmagnesium bromide give an adduct much more reactive than N-methylindole itself was supported by the results of a theoretical investigation. The structure and electron distribution of the adduct were determined by ab initio calculations and compared with those of known Grignard complexes with nitrogen ligands. The performance of different basis sets was tested. The quantum theory of atoms in molecules was used to determine atomic charges and to describe the nature of bonds in terms of the properties of the electron density at the bond critical points.

Stereoelectronic effects in polythiophenes: poly(3-cyclopropylthiophene) and poly (3-cyclobutylthiophene)

Stereoelectronic effects enable 3-cyclopropyl and 3-cyclobutylthiophene to produce electrochemical polymers. Poly(3-cyclopropylthiophene) is the only good electroconducting poly(3-alkylthiophene) with a branched carbon directly connected to the thiophene ring.

Conformational effects on electrical and spectroscopic properties of bi-, ter-, and poly-thiophenes

Using conformatcnally constrained bi- and ter-thiophenes, the effects of inter-ring torsional angles on spectroscopic properties of the corresponding polymers are demonstrated; effects on conductivity are complicated by inter-chain contributions.