A facile Garratt-Braverman cyclization route to intercalative DNA-binding bis-quinones

Bispropargyl ethers (both symmetrical and non-symmetrical) equipped with 1,4-dimethoxyaryl groups were synthesized. Under strongly basic conditions (KOBut/toluene/reflux), these ethers underwent Garratt-Braverman type cyclization to the tetramethoxy bi-aryl systems in high yields presumably via the bisallenes. The products could be successfully converted to the bis-quinones via CAN-mediated demethylation cum oxidation. This two-step protocol offers a simple route to bis-quinones, connected by C1-C2′ bonds, in good yields. Fluorescence based EB-displacement assay, CD spectroscopy and viscosity measurements confirmed the DNA-binding ability of the synthesized quinones via intercalation.