Reductive Coupling of 2-Propyn-1-ones Promoted by Yb Metal or YbCl3–Zn

Abstract
Ytterbium metal promotes reductive coupling of 2-propyn-1-ones (1) to give cyclobutenes and 1,6-dioxo-2,4-hexadiene, whereas 1 is converted to 2,5-dihydrofurans on the treatment with YbCl3–Zn.