Lithium-mediated mechanochemical annulative dimerization of diarylacetylenes for synthesis of 1,4-dihydrodinaphthopentalenes

Abstract

1,4-Dihydrodiarenopentalenes, the reduced derivatives of diarenopentalene, have attracted attention owing to their rigid planar π-conjugated ladder framework, photophysical properties, C₂-chiral structure, and potential applications in physical organic chemistry and materials science. Unlike the established methods for parent diarenopentalenes, the synthetic method for 1,4-dihydrodiarenopentalenes is less established, and the constructed structures are highly limited to dihydrodibenzopentalenes with trialkylsilyl substituents. Herein, we report a novel method for synthesizing 1,4-dihydrodinaphthopentalene derivatives by mechanochemical annulative dimerization of 2-(arylethynyl)naphthalenes with a lithium(0) wire. This reaction is easy to handle—even in an ambient atmosphere at room temperature—and requires a minimum amount of tetrahydrofuran for efficient grinding, resulting in the formation of various 1,4-diaryl-1,4-dihydrodinaphthopentalenes within 15 min. Furthermore, structural and theoretical analyses, as well as photophysical and chiro-optical measurements, reveal untapped properties of chiral 1,4-dihydrodinaphthopentalene.