Unexpected One-Pot Synthesis of Highly Conjugated Pentacyclic Diquinoid Compounds

A new class of pentacyclic diquinoid compounds has been
synthesized
with a facile one-pot reaction of two molecules of 2-hydroxynaphthoquinone
and 1-bromoalkanes in the presence of ferrocene. These molecules were
isolated as enol tautomers that exhibit intramolecular hydrogen bond
and extended electronic conjugation as proved by the intense absorption
spectrum with a broad band between 400 and 600 nm. The spectroscopic
and electrochemical characterization of this new class of compounds
has been performed. One of the synthesized diquinoid derivatives showed
a significant cytotoxicity with IC50 values of 25–50
μM against Cisplatin-Resistant SKOV3 and colon carcinoma SW480
cell lines. The results of our study provide a valuable tool to a
one-pot synthesis of highly conjugated polyquinones, analogous to
important biological systems, with significant antitumoral activity.