METHYLATION OF METALATED INDENE AND METHYLINDENE

The reaction of metallic lithium and potassium with indene and fluorene in refluxing 1,2-dimethoxyethane (DME) yields reduction products of indene and fluorene, 1-metalated indene, and 9-metalated fluorene, and as well is accompanied by the production of some hydrogen gas due to the acidic methylene group. The amount of hydrogen is small for fluorene but quite substantial for indene.Metalation of indene, 1-methylindene, and 3-methylindene in refluxing DME, followed by methylation of these metalated indenes at 0°, gave a mixture consisting of starting material, the corresponding indan, monomethylindene, dimethylindene, and in some cases trimethylindene. Two competing reaction mechanisms resulting in the formation of the metalated indenes are suggested and possible routes for the formation of the di- and tri-methylindenes are examined.