Phenantridine derivatives

Oxoniachrysenes 67 are simultaneously 2-benzopyrylium and 1-benzopyrylium salts, but maintain a distinct chemical behavior. 5-Oxoniachrysene salts 67 are interesting mainly as precursors of ben-zo[c]phenantridine derivatives 132, as mentioned in Section II,C,6. However, in contrast to 2-benzopyrylium salts (cf. Section III,C,4,a), compounds 67 react with nitrogen nucleophiles to form stable adducts 131 or products of anomalous ring-opening, namely a-naphthols 66 and esters 70 (77KGS1176). 

In this context aryllithiums are also able to carbolithiate a benzyne moiety, and so we have also described the preparation of several phenantridine, dibenzopyran and diben-zothiopyran derivatives 383. In these cases y-functionalized organolithiums, derived from bromides 382, afford the corresponding and regiospecifically functionalized six-membered benzofused N-, O- or S-heterocycles through a 6-exo cyclization reaction onto a benzyne intermediate (Scheme 101)161b. 

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