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Stereocontrolled Synthesis of Chiral Heteroaromatic Propellers with Small Optical Bandgaps
Author(s) -
Navakouski Maksim,
Zhylitskaya Halina,
Chmielewski Piotr J.,
Lis Tadeusz,
Cybińska Joanna,
Stępień Marcin
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201900175
Subject(s) - steric effects , electrophile , stereoselectivity , chemistry , enantiomer , bromine , surface modification , combinatorial chemistry , oxidative coupling of methane , electrochemistry , propeller , photochemistry , stereochemistry , organic chemistry , catalysis , electrode , marine engineering , engineering
Abstract Chiral heteroaromatic propellers based on radially π‐extended hexapyrrolohexaazacoronenes were obtained in a concise synthesis from suitably functionalized donor–acceptor monopyrroles. To overcome steric hindrance, a new cyclodehydrogenation method was developed, and it uses bromine electrophiles as oxidative coupling agents instead of the commonly employed high‐potential oxidants. The new reaction offers high yields of propeller‐shaped targets, even for electron‐deficient precursors, and shows electrophile‐dependent stereoselectivity, with N ‐bromosuccinimide and dibromine yielding, respectively D 6 ‐ and C 2 ‐symmetric products. The propeller azacoronenes are chiral and can be separated into configurationally stable enantiomers. In addition to providing steric bulk, peripheral functionalization considerably affects the electronic properties of the propellers, which exhibit reduced optical and electrochemical band gaps, and a more clearly defined electroreduction behavior.