1,3‐Diethynylallenes (DEAs): Enantioselective Synthesis, Absolute Configuration, and Chiral Induction in 1,1,4,4‐Tetracyanobuta‐1,3‐dienes (TCBDs)

Abstract

Optically active 1,3-diethynylallenes (DEAs) were prepared by enantioselective Pd-mediated SN2′-type cross-coupling and their absolute configuration was determined by X-ray analysis. Addition of tetracyanoethene (TCNE) to donor-substituted DEAs affords novel 1,1,4,4-tetracyanobutadiene (TCBDs)-based charge-transfer chromophores in high yield. CD spectroscopy reveals strong chiral induction from the optically pure allene into the directly adjacent TCBD moieties.