Novel methodology for the synthesis of the benzo[b]phenanthridine and 6H-dibenzo[c,h]chromen-6-one skeletons. Reactions of 2-naphthylbenzylamines and 2-naphthylbenzyl alcohols

Novel syntheses of both the benzo[b]phenanthridine and the 6H-dibenzo[c,h]chromen-6-one motif are described. Reaction of (2-(3-bromo-1,4-dimethoxynaphthalen-2-yl)phenyl)methanamine with PIFA afforded benzo[b]phenanthridine-7,12-dione, while the related nonbrominated precursor, (2-(1,4,5-trimethoxynaphthalen-2-yl)phenyl)methanamine on treatment with PIFA, furnished the ortho-quinone 1-methoxybenzo[c]phenanthridine-11,12-dione. Unexpectedly, treatment of related oxygen analogs such as (2-(1,4-dimethoxynaphthalen-2-yl)phenyl)methanol with NBS under an O2 atmosphere, afforded a chromenone, 12-methoxy-6H-dibenzo[c,h]chromen-6-one.