Cooperative activation of azides by an Al/N-based active Lewis pair – unexpected insertion of nitrogen atoms into C–Si bonds and formation of AlCN3 heterocycles

The active Lewis pairs (ALPs) 2,6-Me₂H₈C₅N–C(H) = C(SiMe₃)–AlR₂ (1a: R = ᵗBu, 1b, R = ⁱBu) have strained AlC₂N heterocycles and relatively weak Al–N bonds. They react readily with a series of organic azides R′N₃ [R′ = Ph, CH₂C₆H₄(4-ᵗBu), ᵗBu, SiMe₃, CH₂Ph] by cleavage of the heterocycles and addition of the azides with their α-N atoms to the Al atom. The Al–N interactions result in an activation of the azide groups which insert into the C–Si bonds of the vinyl groups with their terminal γ-N atoms. Compounds with approximately planar five-membered AlCN₃ heterocycles and intact N₃ groups are formed in highly selective reactions.