POTASSIUM DERIVATIVES OF FLUORENE AS INTERMEDIATES IN THE PREPARATION OF C9-SUBSTITUTED FLUORENES: III. THE INFLUENCE OF SOLVENT AND METAL IN THE FORMATION OF C9-SUBSTITUTED FLUORENES FROM 9-FLUORENYL METALS

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Abstract
Equimolar quantities of 9-fluorenyl-potassium, -sodium, or -lithium and alkyl or aralkyl halides at room temperature in ether solvents yielded a mixture of unchanged fluorene, C9-monosubstituted fluorene, and C9-disubstituted fluorene. The amount of disubstitution never exceeded that of unchanged fluorene, and was found to be maximum (∼35%) for the potassium compound in 1,2-dimethoxyethane, somewhat less for the sodium analogue, and small (∼5%) for the lithium compound. In hydrocarbon solvents such as hexane, 9-fluorenylpotassium gave only 7% of C9-disubstituted fluorene. The lithium compound, upon reaction with methyl iodide or ethyl iodide gave, along with unreacted fluorene, only C9-monosubstituted fluorene. But reaction of 9-fluorenyllithium with benzyl chloride in hexane gave a small quantity (∼5%) of disubstituted fluorene as well as the monosubstituted product.The results are explained in terms of (a) the solubilities of the organometallic compounds in ether and hydrocarbon solvents, (b) the polarity of the metal carbon bond, and (c) the acidity of the hydrogen on C9 of fluorene.