Synthesis of pentacyclic 13-azadibenzo[a,de]anthracenes via anionic cascade ring closure.
Bromine-lithium exchange using tert-butyllithium at -78 degrees C initiates a cascade process whereby either xanthone derivatives or pentacyclic 13-azadibenzo[a,de]anthracenes are produced in high yields. The reaction proceeds via a sequential intramolecular trapping of organolithium intermediates.
Kristensen
Jesper L
JL
Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, 2100 Copenhagen, Denmark. jekr@dfh.dk
Vedsø
Per
P
Begtrup
Mikael
M