An Aluminium Imide as a Transfer Agent for the [NR]2−Function via Metathesis Chemistry

Abstract

AbstractThe reactions of a terminal aluminium imide with a range of oxygen‐containing substrates have been probed with a view to developing its use as a novel main group transfer agent for the [NR]2−fragment. We demonstrate transfer of the imide moiety to [N2], [CO] and [Ph(H)C] units driven thermodynamically by Al−O bond formation. N2O reacts rapidly to generate the organoazide DippN3(Dipp=2,6‐iPr2C6H3), while CO2(under dilute reaction conditions) yields the corresponding isocyanate, DippNCO. Mechanistic studies, using both experimental and quantum chemical techniques, identify a carbamate complex K2[(NON)Al‐{κ2−(N,O)−N(Dipp)CO2}]2(formed via [2+2] cycloaddition) as an intermediate in the formation of DippNCO, and also in an alternative reaction leading to the generation of the amino−dicarboxylate complex K2[(NON)Al{κ2−(O,O′)−(O2C)2N‐(Dipp)}] (via the take‐up of a second equivalent of CO2). In the case of benzaldehyde, a similar [2+2] cycloaddition process generates the metallacyclic hemi‐aminal complex, Kn[(NON)Al{κ2−(N,O)−(N(Dipp)C(Ph)(H)O}]n. Extrusion of the imine, PhC(H)NDipp, via cyclo‐reversion is disfavoured thermally, due to the high energy of the putative aluminium oxide co‐product, K2[(NON)Al(O)]2. However, addition of CO2allows the imine to be released, driven by the formation of the thermodynamically more stable aluminium carbonate co‐product, K2[(NON)Al(κ2−(O,O′)−CO3)]2.