A Convenient One-Pot Synthesis of a Sterically Demanding Aniline from Aryllithium Using Trimethylsilyl Azide, Conversion to <i>β</i>-Diketimines and Synthesis of a <i>β</i>-Diketiminate Magnesium Hydride Complex

Abstract

This work reports the one-pot synthesis of sterically demanding aniline derivatives from aryllithium species utilising trimethylsilyl azide to introduce amine functionalities and conversions to new examples of a common N,N′-chelating ligand system. The reaction of TripLi (Trip = 2,4,6-iPr3-C6H2) with trimethylsilyl azide afforded the silyltriazene TripN2N(SiMe3)2 in situ, which readily reacts with methanol under dinitrogen elimination to the aniline TripNH2 in good yield. The reaction pathways and by-products of the system have been studied. The extension of this reaction to a much more sterically demanding terphenyl system suggested that TerLi (Ter = 2,6-Trip2-C6H3) slowly reacted with trimethylsilyl azide to form a silyl(terphenyl)triazenide lithium complex in situ, predominantly underwent nitrogen loss to TerN(SiMe3)Li in parallel, which afforded TerN(SiMe3)H after workup, and can be deprotected under acidic conditions to form the aniline TerNH2. TripNH2 was furthermore converted to the sterically demanding β-diketimines RTripnacnacH (=HC{RCN(Trip)}2H), with R = Me, Et and iPr, in one-pot procedures from the corresponding 1,3-diketones. The bulkiest proligand was employed to synthesise the magnesium hydride complex [{(iPrTripnacnac)MgH}2], which shows a distorted dimeric structure caused by the substituents of the sterically demanding ligand moieties.

Keywords

• aniline synthesis
• azides
• <i>β</i>-diketiminates
• magnesium hydride
• metal-halogen exchange
• organolithium reagents