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.