The 2-Chloro-2-propenyl Side Chain. A Useful Acetic Acid Equivalent

Abstract

The introduction of an acetic acid side chain via enolate alkylation has found widespread application in the synthesis of natural products, especially in the area of fused-ring γ-butyrolactones.¹ While the direct approach using α-haloacetic esters as alkylating agents usually yields satisfactory results, the use of an acetic acid equivalent (synthon)² may sometimes be necessary in order to permit selective manipulations of polyfunctional intermediates. On such occasions, allyl (2-propenyl) or substituted allyl groups have been employed with good success.³ We recently encountered problems with the oxidative cleavage of allyl side chains which prompted us to utilize 2-chloro-2-propenyl as an acetic acid synthon, with excellent results.