The protection of aminophenyl groups in organometallic syntheses

Abstract

The trimethylsilyl group can be used to protect aminophenyl groups in organometallic transformations as follows: p-Li·C₆H₄·N(SiMe₃)₂, prepared from p-Br·C₆H₄·N(SiMe₃)₂ and lithium or n-butyl-lithium, couples normally with halogeno-silanes and -germanes and with carbonyl compounds. The intermediates can be isolated, [p-R₃M·C₆H₄·N(SiMe₃)₂ : R₃M = Me₃Si or Et₃Ge] and methanolysed, or hydrolysed directly to the free amines [p-R₃M·C₆H₄·NH₂; p-NH₂·C₆H₄·C(OH)PhR′: R′= H or Ph]. A Wurtz–Fittig coupling reaction between m-Cl·C₆H₄N(SiMe₃)₂ and Me₃SiCl gave m-Me₃Si·C₆H₄·N(SiMe₃)₂ which on solvolysis afforded m-Me₃Si·C₆H₄·NH₂.