Design and Synthesis of <i>C</i>₃-Symmetric Chiral Dopants for Nematic Liquid Crystals Based on the I₂-Promoted Cyclodearomatization of Alkyne-Linked Benzofurans

For the efficient geometry control of chiral nematic liquid crystals (N*LCs), a variety of chiral furopyran derivatives <b>1</b> with three aromatic groups fixed in a pseudo-<i>C</i>₃-symmetric fashion was designed as novel chiral dopants (CDs) and successfully synthesized from the alkyne-linked benzofuran systems <b>2</b> in excellent yields by the newly developed I₂-promoted iodination-dearomatizative [4 + 2] cycloaddition cascade reaction. The subsequent structural diversification of the thus obtained <b>1</b> was achieved by various coupling methods applied for the iodoalkene moiety. The high performance of <b>1</b> as CDs was demonstrated in JC-1041XX/5CBs (1:1 wt ratio) as achiral host LCs, leading to the discovery of <b>1el</b> with a naphthofuran and long-chain alkyl unit that exhibited an extremely large molecular helical twisting power (molecular HTP or β_M) of -203 μm^-1 and produced cholesteric blue phases (BP I and BP II), namely, N*LC phases, comprising a higher-order supramolecular network.