Patent ID: 7696356

Claim:
A process for preparing 1,2,3,9-tetrahydro-9-methyl-3-methylene-4H-carbazol-4-one, comprising the steps of: (a) preparing a mixture of 1,2,3,9-tetrahydro-9-methyl-4H-carbazol-4-one, a formaldehyde reagent, and a mineral acid in an aprotic solvent; (b) heating the mixture for about 1 hour to about 8 hours to provide 1,2,3,9-tetrahydro-9-methyl-3-methylene-4H-carbazol-4-one; and (c) isolating the 1,2,3,9-tetrahydro-9-methyl-3-methylene-4H-carbazol-4-one; wherein the mixture further comprises an ammonium salt.