Trifluoromethoxy Substituted Anilines: Metalation as the Key Step for Structural Elaboration

Trifluoromethoxy-substituted anilines undergo hydrogen/lithium permutation ("metalation") with optional site selectivity depending on the N-protective group employed. N-tert-Butoxycarbonyl-2- and -4-(trifluoromethoxy)aniline react with tert-BuLi at the nitrogen-adjacent 6- and 2-position affording, after electrophilic trapping, the corresponding substituted anilines I (R1 = F3CO, R2 = H, R3 = HO2C; R1 = H, R2 = F3CO, R3 = Me, CHO, HO2C, HOCH2CH2). In contrast, deprotonation of the N,N-bis(trimethylsilyl)-substituted 4-(trifluoromethoxy)aniline occurs at the oxygen-neighboring 3-position. Sec-BuLi attacks 3-trifluoromethoxy-N-(trimethylsilyl)aniline at the 2-position, but 3-trifluoromethoxy-N,N-bis(trimethylsilyl)aniline at the 4-position to provide the corresponding acids II (R4 = HO2C, R5 = H; R4 = H, R5 = HO2C), resp., after carboxylation. The synthesis of two new benzodiazepines III (R6 = F3CO, R7 = H, R8 = F; R6 = Cl, R7 = HO, R8 = F3CO) illustrates the preparative potential of the aniline functionalization mediated by organometallic reagents. [on SciFinder (R)]