Carbene-Stabilized Aluminacyclopropene–Cyclopropenylalane Rearrangement

A direct [1 + 2] cycloaddition reaction between an N-heterocyclic
carbene-stabilized acyclic aluminylene and bis(trimethylsilyl)acetylene
leads to the formation of neutral aluminacyclopropene, compound 2. However, this compound demonstrates thermal instability
in solution, resulting in an aluminacyclopropene–cyclopropenylalane
rearrangement. This transformation exemplifies a formal constitutional
isomerization between the C–AlC2 and Al–C3 systems. Density functional theory computations provide insights
into the mechanism behind this unique rearrangement. Our findings
contribute a novel aspect to the recent observation that N-heterocyclic
carbenes can act as single-carbon-atom sources.