Periselectivity switch of acylketenes in cycloadditions with 1-azadienes: microwave-assisted diastereoselective domino three-component synthesis of α-spiro-δ-lactams.

The microwave-assisted Wolff rearrangement of cyclic 2-diazo-1,3-diketones in the presence of primary amines and α,β-unsaturated aldehydes provides a straightforward three-component stereoselective access to a variety of α-spiro-δ-lactams following an imination/Wolff rearrangement/[2 + 4] cycloaddition domino sequence. With aniline derivatives, a complementary aza-Wittig/Wolff rearrangement/[2 + 4] sequence was developed. These reactions feature an unprecedented reactivity of acylketenes as dienophiles in 6π electrocyclic processes.