V. Gevorgyan et al., Synthesis of cyclophanes via an intermolecular Pd-catalyzed enyne-diyne cross-benzannulation approach, J ORG CHEM, 66(8), 2001, pp. 2743-2746
Several novel types of cyclophanes were efficiently synthesized via an inte
rmolecular palladium-catalyzed cross-benzannulation of cyclic enynes and di
ynes. These types of cyclophanes are not accessible through an intramolecul
ar mode of the homo-benzannulation protocol, reported previously. Cyclic re
actants (enynes and diynes) were readily prepared in reasonable yields from
commercially available materials using known procedures. The fact that the
cyclic Z-enyne 29, in contrast to its E-counterpart, underwent benzannulat
ion to produce the cyclophane 28 brought additional support for the necessi
ty of having an E-hydrogen atom at the terminal olefin moiety of nonactivat
ed enynes, which was found previously in the benzannulation of the acyclic
susbstrates.