Formal Intramolecular [4 + 1]-Cycloaddition of Dialkoxycarbenes: Control of the Stereoselectivity and a Mechanistic Portrait.

A variety of electron-deficient dienes bearing a 2,2-dialkoxy-Δ3-1,3,4-oxadiazoline moiety as source for the dialkoxycarbene is transformed to cyclopenta-fused five-, six-, and seven-membered O-heterocyclic rings.