Catalyst-Controlled Chemoselective All-Alkene [2 + 2 + 2] and [2 + 2] Cyclizations of Enamides with Electron-Deficient Alkenes.

In the presence of 4 Å MS, both all-alkene [2 + 2 + 2] and [2 + 2] cyclizations of dimethyl methylenemalonate (DMM) with N-sulfonyl enamides were selectively achieved under In(OTf)3 and Cu(OTf)2 catalysis, respectively. In(OTf)3-catalyzed [4 + 2] cyclization of the sulfonylamidocyclobutanes with another molecule of DMM or other electron-deficient alkenes was also reported.