A simple reagent, N‐bromosuccinimide, is the oxidant of choice in the stereospecific synthesis of azacoronene propellers. This new family of chiral chromophores features small electronic bandgaps, rich redox chemistry, and large chiroptical responses.
This review summarizes recent advances in the chemistry of curved aromatic molecules. By focusing on the key accomplishments of the last decade, we provide a general overview of synthetic methods capable of efficient induction of internal strain in π‐conjugated frameworks. The review is structured according to the topology change involved in the strain‐inducing reaction step (cyclizations, eliminations, ring expansions and contractions), and highlights the striking diversity of structures achievable with modern synthetic methodology.
Chrysaorenes and their macrocyclic precursors do not usually swarm on your floor. However, to prepare yourself for the encounter, you may wish to read the paper nevertheless.
Deep, fluorescent aromatic bowls, resembling carbon nanotube endcaps, are prepared by Ni(0)-mediated coupling of simple heterocyclic precursors. This one-step synthesis, capable of introducing an unprecedented amount of internal strain, relies on accurate timing of transmetalation and reductive elimination steps.
Chrysaorole,* which is a jellyfish‐shaped strained heteroaromatic molecule, was obtained from a carbazole‐based macrocyclic precursor by using a new “fold‐in” strategy.*after Chrysaora, a genus of jellyfish. Χρυσάωρ“golden armament” .
The image shows the host–guest interaction between the figure‐eight dication of di‐p‐benzihexaphyrin and a dichloroacetate anion. For details see Section 6.5 of this review.
The two complementary worlds of π aromaticity meet in one molecule. Di‐p‐benzihexaphyrin contains two phenylene rings, which, when oriented face‐to‐face, define an antiaromatic macrocycle with an orientable (Hückel) π system. With a 90° twist of one phenylene ring, the molecule transforms into a remarkable edge‐to‐face conformer with a Möbius topology. The different colors of the two forms show the effect of topology switching on the π conjugation. .
The two inner protons of 22-hydroxybenziporphyrin, a phenol-containing porphyrin analogue, act as a switch of antiaromaticity. This unusual example of keto-phenol tautomerization, which interchanges - and annulenoid conjugation pathways, has been investigated by means of NMR spectroscopy and computational methods. .