Direct Synthesis of Benzo[c]carbazoles by Pd-Catalyzed C-H [4 + 2] Annulation of 3-Arylindoles with External 1,3-Dienes.

Herein, we present a regioselective Pd-catalyzed C-H [4 + 2] benzannulation of N-unprotected 3-arylindoles with external readily available 1,3-dienes via an original sequence involving a Pd-catalyzed domino carbopalladation of 1,3-dienes/direct C2-H allylation of an indole ring followed by an oxidation or reduction step. Depending on the nature of the solvent, DCE or CH3CN, two consecutive approaches, oxidative or reductive, have been validated and applied to the design of a novel library of C6-alkyl or (E)-C6-styryl-benzo[c]carbazoles in moderate to good yields.

V-shaped 4,6-bis(arylvinyl)pyrimidine oligomers: synthesis and optical properties.

A series of V-shaped 4,6-bis(arylvinyl)pyrimidines have been efficiently prepared by aldol condensation between 4,6-dimethylpyrimidine and the appropriate aromatic aldehyde. The methodology also proved successful when dendritic first generation poly(phenylenevinylene) aldehydes were used. Moreover, asymmetrically functionalized molecules were also obtained by the stepwise incorporation of arms in a controlled manner. The optical absorption and emission properties of these systems were studied in different solvents and media. The materials display strong emission solvatochromism that is reflected by a large red shift in their fluorescence emission maxima on increasing the solvent polarity. This change is accompanied by a successive decrease in fluorescence intensity. This behavior suggests a highly polar emitting state, which is characteristic of compounds that undergo an internal charge transfer upon excitation. The abilities of these molecules to function as colorimetric and luminescence pH sensors were demonstrated with dramatic color changes and luminescence switching upon the introduction of acid.

New [4.4]cyclophanes: molecular parallelograms, triangles, rhombuses, pentagons, and supramolecular constructions.

The fair or good yield synthesis of new [(4.4)(n)]cyclophanes (n = 1-5), starting from 1,4-bis(2-hydroxymethyl-5,5-dimethyl-1,3-dioxan-2-yl)benzene and several diacid-dichlorides, based on monomer and oligomer formation reactions (from 1 + 1 to 5 + 5), is reported. The structure and the complex architectures of the lattices for these cyclophanes are revealed by the X-ray molecular structure for five compounds, NMR investigations, and mass spectrometry measurements. Intramolecular and intermolecular CH-pi, p-pi, and pi-pi interactions are observed, both in solid state and solution.

Molecular rotors: design, synthesis, structural analysis, and silver complex of new [7.7]cyclophanes.

New molecular rotors, [7.7](2,6)pyridinocyclophanes (monomers and dimers) embedding 1,3-dioxanes in the bridges, were investigated by variable-temperature NMR, molecular modeling, and single-crystal X-ray diffractometry. The nitrogen-inside rotation of the pyridine ring is more hindered in the derivatives with longer distance between the bridges (i.e., para > meta and 2,6-pyridylene > ortho) and can be chemically stopped by complexation with CF(3)SO(3)Ag. [structure: see text]

Design and synthesis of new macrocyclic cyclophanes using 1,3-dioxane units as bridges: a molecular "rocking chair".

The design, synthesis and structural analysis of architecturally new cyclophanes (monomers, dimers, and trimers) are reported. Variable temperature NMR experiments reveal a regular, tandem dynamic in the cyclophane 2a that enables its description as a "molecular rocking chair". The NMR and X-ray structure investigations show important intra- and intermolecular aromatic pi-stacking interactions.