Preparation of pyrrolo[3,2,1-jk]carbazole by nickel(0) mediated ring contraction of pyrrolo[3,2,1-kl]phenothiazine. Proton NMR and mass spectral studies

Pyrrolo3,2,1-jk]carbazole 1a , the previously unreported 16π-electron parent compound, has been synthesized by treatment of pyrrolo3,2,1-kl]phenothiazine 2a with a 1:1 mixture of bis(1,5-cyclooctadiene) nickel(0) and 2,2′-bipyridyl. An unequivocal assignment of the ¹H nmr spectrum of 1a was made by decoupling experiments and by comparison with the ¹H nmr spectrum of 1,9-dideuteriopyrrolo3,2,1-jk]carbazole 1b . Metastable ion studies, exact mass measurements and the dideuterioderivative 1b were utilized to investigate the electron impact induced fragmentation of 1a .