A novel C-N cleavage in isoquinolines allowing the first direct transformation of 1-benzylisoquinolines into benzo[c]phenanthridines and a new route to 2-phenyl-1,4-naphthoquinones

Treatment of N-carbethoxy-1-benzylideneisoquinolines with LDA gives N-ethox ycarbonyl-1-amino-1-(2-vinylphenyl)-2-phenylethylenes, which can easily be transformed into N-carbethoxy-1-amino-2-phenylnaphthalenes. Bichler-Napiera lski reaction of these latter compounds affords the corresponding benzo[c]p henanthridines, while their hydrolysis and subsequent oxidation constitutes a route to 2-phenyl-1,4-naphthoquinones. (C) 2000 Elsevier Science Ltd. Al l rights reserved.