Arene 1,4-Diradical Formation from o-Dialkynylarenes

A series of 10-membered cyclic 1,5-diynes has been prepared with arene rings fused at positions C-3/C-4. The arenes include simple benzene rings, a naphthoquinone and naphthohydroquinone, and an anthraquinone and anthracene unit. Consistent with a simple picture relating the extent of double bond character in the ene part of the ene-diyne with the rate of arene-1,4-diyl formation, the hydroquinone derivatives were much less reactive compared to the corresponding quinones. Substituents such as propargylic hydroxyl or keto group have a small but significant activating effect. The parent 3,4-benzo-1,8-decadiyne shows a half-life for rearrangement of 24 h at 84 °C while the corresponding alkene, cyclodec-3-ene-1,5-diyne is reported to have a half-life of 18 h at 37 °C.