When lb was treated with P4OlO in refluxing benzene, a 70% yield of N-benzoylcarbazole (2b) was produced. The tosylhydroxylamine IC cyclized to N-tosylcarbazole (2c) in 55% yield under similar conditions. Hot polyphosphoric acid (PPA) was also effective: IC in hot PPA gave 2c in 46% yield. Hot PPA was not useful for the cyclization of 1 b since the product, N-benzoylcarbazole (2b), was unstable in hot PPA. A separate experiment ...