Six different fluoroarenes were submitted to the same transformations. Direct deprotonation with alkyllithium or lithium dialkylamide as reagents and subsequent carboxylation afforded acids. These included 2,6-difluorobenzoic acid, 3,6-difluoro-2-iodobenzoic acid, 2-fluoro-6-iodobenzoic acid, 2-fluoro-3-iodobenzoic acid, 2,3-difluoro-4-iodobenzoic acid and 1-fluoro-2-naphthalenecarboxylic acid. If the aryllithium intermediate was trapped with iodine rather than with dry ice, an iodofluoroarene (2, 7, 12, 17, 19, and 24) was formed. Iodoarenes included 1,3-difluoro-2-iodobenzene, 1,4-difluoro-2,3-diiodobenzene, 1-fluoro-2,3-diiodobenzene, 2-fluoro-1,3-diiodobenzene, 2,3-difluoro-1,4-diiodobenzene, and 1-fluoro-2-iodonaphthalene. These, upon treatment with lithium diisopropylamide, underwent deprotonation and iodine migration. The resulting new aryllithium species was intercepted either by carboxylation, to give 2,6-difluoro-3-iodobenzoic acid, 2,5-difluoro-3,6-diiodobenzoic acid, 2-fluoro-3,6-diiodobenzoic acid, 2,3-difluoro-4,6-diiodobenzoic acid, and 1-fluoro-3-iodo-2-naphthalenecarboxylic acid, or by neutralization to produce the iodofluoroarenes which included 2,4-difluoro-1-iodobenzene, 1,4-difluoro-2,5-diiodobenzene, 2-fluoro-1,4-diiodobenzene, 1-fluoro-3-iodonaphthalene. The latter family of compds. was converted into another set of acids, which included 2,4-difluorobenzoic acid, 2,5-difluoro-4-iodobenzoic acid, 1-fluoro-3-naphthalenecarboxylic acid, by subsequent treatment with butyllithium or isopropylmagnesium chloride and carbon dioxide. [on SciFinder (R)]
