Studies in the Indole Series. II. A General Synthesis of Cycloalkan[b]indolones

A general synthesis of cycloalkan[b]indolones from 3-indolealkanoic acids is described. Effect of 1-alkyl substitution of indole was observed on the ultraviolet spectra of 1-methyl-3-indolealkanoic acids. Cyclization of 3-indolealkanoic acids was mostly effected with polyphosphoric acid. Ring closure of Vc and Vd with PPA brought about concomitant expected monomers (VIIc and VIId) and dimers (VIIIa and VIIIb). The structure proof of the dimers was obtained from analytical and spectral data.