3-Diazotetramic acids were found to be valid
substrates for the recently discovered approach toward natural-
like Δ α,β -spirobutenolides via Rh(II)-catalyzed O−H insertion into
propiolic acids followed by base-promoted intramolecular Michael
addition. The target Δ α,β -spirobutenolides were obtained in
generally high yields and, in the case of chiral 5-monosubstituted
3-diazotetramic acids, high diastereoselectivity. The synthesis of
Δ α,β -spirobutenolides that we report here was virtually insensitive
to the structure of the propiolic acids though it was somewhat sensitive to the structure of the 3-diazotetramic acids, thereby
demonstrating quite a large scope. Thus, a new class of α-diazocarbonyl compounds suitable for the realization of the approach
outlined above was identified.