ChemInform Abstract: Synthesis and Properties of Methano Bridged Tetradehydro‐(18)annulene, ‐(20)annulene, ‐(22)annulene, ‐(24)annulene, and the Related (1,3)Cyclophanpolyenediyne Compounds.

Abstract The title annulenes (III) are obtained by Wittig reaction of the dialdehydes (I) with the phosphonium salt (II).