Several novel types of cyclophanes were efficiently synthesized via an intermolecular palladium-catalyzed cross-benzannulation of cyclic enynes and diynes. These types of cyclophanes are not accessible through an intramolecular mode of the homo-benzannulation protocol, reported previously. Cyclic reactants (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 benzannulation to produce the cyclophane 28 brought additional support for the necessity of having an E-hydrogen atom at the terminal olefin moiety of nonactivated enynes, which was found previously in the benzannulation of the acyclic susbstrates.
ASJC Scopus subject areas
- Organic Chemistry