Synthesis of β, γ-Unsaturated Valerolactones

Abstract

In recent years various attempts have been made to use reagent equivalents¹) in order to effect reactions which are not otherwise accessible by means of conventional reagents. Particularly it is to be noted that synthetic equivalents for unreactive dienophiles, such as carbon dioxide,^2,3,4) ketene,^3,5) allene,⁶⁾ and acetylene,⁷⁾ have greatly extended the scope of the cycloaddition reactions into systems not normally generated by the thermal process.