Synthesis of Aza[n]helicenes (n = 4-7) via Photocyclodehydrochlorination of 1-Chloro-N-aryl-2-naphthamides

Resolution of 9,10-Diketo[7]helicene and Its Use in One-Step Preparation of Helicene-Based D-A-D Push-Pull Systems

Racemic 9,10-diketo[7]helicene was successfully separated into enantiomers using a reversible and stereoselective reaction with 2,2'-diamino-1,1'-binaphthalene with moderate yields but with remarkable purity (>99% de). The enantiomerically pure diketone was used as a convenient starting material for the preparation of helicene-based push-pull molecules, which incorporated aza-aryl acceptors and diarylaminophenylene donor groups in a single step. A series of six push-pull systems, along with three reference molecules without donors, were prepared and studied using UV/vis and fluorescence measurements, circular dichroism, and DFT calculations.

Adsorption and Self-Aggregation of Chiral [5]-Aza[6]helicenes on DNA Architecture: A Molecular Dynamics Study

Helicenes are an extremely interesting class of conjugated molecules without asymmetric carbon atoms but with intrinsic chirality. These molecules can interact with double-stranded chiral B-DNA architecture, modifying after their adsorption the hydrophilicity exposed by DNA to the biological environment. They also form ordered structures due to self-aggregation processes with possible different light emissions. Following initial studies based on molecular mechanics (MM) and molecular dynamics (MD) simulations regarding the adsorption and self-aggregation process of 5-aza[5]helicenes on double-stranded B-DNA, this theoretical work investigates the interaction between (M)- and (P)-5-aza[6]helicenes with double-helix DNA. Initially, the interaction of the pure single enantiomer with DNA is studied. Possible preferential absorption in minor or major grooves can occur. Afterward, the interaction of enantiopure compounds (M)- and (P)-5-aza[6]helicenes, potentially occurring in a racemic mixture at different concentrations, was investigated, taking into consideration both competitive adsorption on DNA and the possible helicenes' self-aggregation process. The structural selectivity of DNA binding and the role of helicene concentration in adsorption and the self-aggregation process are interesting. In addition, the ability to form ordered structures on DNA that follow its chiral architecture, thanks to favorable van der Waals intermolecular interactions, is curious.

Construction and Phosphorescence Behavior of S/Se-Heteroaromatics/Phenanthrene-Fused Hetero[9]helicenes

Three S/Se-hetero[9]helicenes were synthesized by an assembly strategy of two building blocks, phenanthrene and ternary fused S/Se-heteroaromatic ring, and characterized by single-crystal X-ray diffraction analysis. Their phosphorescence emission gave a long-lived lifetime at the millisecond level. In addition, the high configurational stability of enantiomer (+)-[9]BH-1a was observed without change under both the conditions of 300 °C in the solid state for 18 h and 200 °C in solution of 1,2-dichlorobenzene for 10 h.

HFIP-promoted halo-carbocyclizations of N- and O-tethered arene–alkene substrates to access all halo (X = Br, I, Cl)-functionalized tetrahydroquinoline and chroman cores

Herein, a HFIP-promoted mild and efficient method for the synthesis of all halo (X = Br, I, Cl)-functionalized tetrahydroquinoline and chroman building blocks is disclosed.