Synthesis, Structures, and Chiroptical Properties of NBN-Doped Helicenes with Boron Atoms in the Inner Rims.

The precise synthesis of helicenes with topologically defined length and specific heteroatomic perturbation in the screw-like conjugated skeletons plays an emerging role in the manipulation of chiral materials. Facile, selective, and programmable routes to helicenes or heterohelicenes are highly desirable yet challenging for structure-chiroptical property relationship studies. Herein, we report the synthesis and characterization of NBN-doped helicenes with boron atoms in the inner rims, enabled by the highly regioselective one-pot borylation of rationally designed precursors with, namely, fold-in or pan-out manner.

Nonalternant B,N-Embedded Helical Nanographenes Containing Azepines: Programmable Synthesis, Responsive Chiroptical Properties and Spontaneous Resolution into a Single-Handed Helix.

Heteroatom-embedded helical nanographenes (NGs) constitute an important and appealing class of intrinsically chiral materials. In this work, a series of B,N-embedded helical NGs (BN-HNGs) bearing azepines was synthesized via stepwise regioselective cyclodehydrogenation. First, the phenyl- or nitrogen-bridged dimers were efficiently clipped into highly congested model compounds 1 and 2.

Nonalternant Nanographenes Containing N-Centered Cyclopenta[]heptalene and Aza[7]Helicene Units.

Introducing helical subunits into negatively curved π-systems has a significant effect on both the molecular geometry and photophysical properties; however, the synthesis of these helical π-systems embedded with nonbenzenoid subunits remains challenging due to the high strain deriving from both the curvature and helix. Here, we report a family of nonalternant nanographenes containing a nitrogen (N)-doped cyclopenta[]heptalene unit. Among them, and can be viewed as hybrids of benzoannulated cyclopenta[]heptalene and aza[7]helicene.