A homologous series of O- and N-functionalized 2,2-difluoro-1,3-benzodioxoles: An exercise in organometallic methodology

The conversion of 2,2-difluoro-1,3-benzodioxole, an exceptionally acidic arene, via a 4-lithiated intermediate into more than three dozen new derivs. was conceived as a case study. The lithiated species was trapped by C0-electrophiles (4-toluenesulfonyl azide, fluorodimethoxyborane, iodine), C1-electrophiles (carbon dioxide, N,N-dimethylformamide, formaldehyde, di-Me sulfate), C2-electrophiles (oxalic acid diesters, oxirane), C3-electrophiles (oxetane), and higher alkyl iodides. The resulting carboxylic acid 2,2-difluoro-1,3-benzodioxole-4-carboxylic acid may be treated with organolithium compds. to afford ketones and the aldehyde 2,2-difluoro-1,3-benzodioxole-4-carboxaldehyde may be condensed with nitromethane or acetic anhydride under basic conditions. If not oxidized with chromium trioxide to the corresponding carboxylic acids, the alcs., e.g., 4-(3-hydroxypropyl)-2,2-difluoro-1,3-benzodioxole can be transformed into the corresponding bromides or sulfonates. Their condensation with nitrogen-contg. C0-nucleophiles (hydroxylamine, sodium azide, potassium phthalimide), C1-nucleophiles (potassium cyanide), and C2-nucleophiles (acetonitrile) opens a convenient access to amines. Other reactions gave, despite a proven track record in other areas, only moderate yields. [on SciFinder (R)]