C-F activation reactions of (pentafluorophenyl)cyclopentadiene and 3-(pentafluorophenyl)indene with tetrakis(dimethylamido)titanium(IV)

Reactions of either 3-(pentafluorophenyl)indene (1a) or (pentafluorophenyl)cyclopentadiene (1b) with Ti(NMe2)(4) afford products in which one or both of the ortho fluorines of the C6F5 group are replaced with a dimethylamino group. The ortho selectivity suggests a titanium-mediated, intramolecular nucleophilic aromatic substitution mechanism. The organic products 3-[2-(dimethylamino)tetrafluorophenyl]indene (4a), 3-[2,6-bis(dimethylamino)trifluorophenyl]indene (7a), and 1-[2,6-bis(dimethylamino)trifluorophenyl]cyclopentadiene (7b) were isolated upon hydrolytic workup. The substituted cyclopentadiene (7b) was converted to the corresponding ferrocene derivative (12) by treatment first with sodium hydride and then with iron dibromide in THF. Three compounds (4a, 7b, and 12) were characterized crystallographically.