1,3-diethynylallenes (DEAs): enantioselective synthesis, absolute configuration, and chiral induction in 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs)

Optically active 1,3-diethynylallenes (DEAs) were prepd. by enantioselective Pd-mediated SN2'-type cross-coupling and their abs. configuration was detd. by X-ray anal. Addn. 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.