Figure 2.

Scope of the Ynamide-[2 + 2] Cycloaddition.

a. All reactions were carried out in anhyd CH₂Cl₂ [ynamide conc = 0.17 M] using 4 Å MS, 20 mol % of CuCl₂, and 60 mol % of AgSbF₆; CuCl₂ and AgSbF₆were premixed at RT for 1 h prior to the addition of a respective ynamide and enone [1.20 equiv] as a combined solution via a syringe pump over 1 h at 0 °C; the reaction was stirred for an additional 30 min to 1 h before isolation. b. Isolated yields.