FACILE SYNTHESES AND MULTI-ORTHOFUNCTIONALIZATIONS OF TERTIARY BENZAMIDES

Abstract

Good yields were usually obtained in Pd(O)-catalyzed Suzuki aryl-aryl coupling reaction, even when both coupling Partners had an ortho tertiary benzamide functional group. The direct ortho functionalization of oligomeric tertiary benzamides at Snieckus condition is dependent on the chain length. Tertiary benzamide 1 can be o,o-dilithiated only by metal-halogen exchange of the 2,6-dihalo-compound. Bis-tertiary benzamide 9 can be o,o'-dilithiated with excess (4.1 equivalents) s-butyllithium/TMEDA as the lithiating agent. Tris-tertiary benzamide 21 is hard to o,o''-difunctionalize due to steric interactions among the tertiary benzamide functional groups, and due to steric interactions between these functional groups and others (if present) on the termini of the terphenyl unit.