Preparation and reactivity of macrocyclic dienynes

Abstract (1 E ,5 E )-Cyclopentadeca-1,5-dien-3-yne ( 1c ), which represents the first macrocyclic 1,5-dien-3-yne, can be obtained by thermal- or butyllithium-induced fragmentation of the corresponding 1,2,3-selenadiazole 8 . The ( E , E )-dienyne functionality causes a geometrical strain E g , which enhances the reactivity in addition ( 1c → 12 , 13 ) and cycloaddition ( 1c → 10 ) reactions and lowers the isomerization barrier to the unstrained ( E , Z )-configuration 1d ( E g  = 0). A slow process 1c → 1d occurs even at ambient temperatures within several weeks.