Enäther als Reaktionspartner von Organometallen II Hydroxyäthyl‐allene und andere Folgeprodukte aus Dihydrofuran‐Derivaten

Upon treatment with organolithium compounds, 2‐alkyl‐4,5‐dihydrofurans undergo ring opening through β‐elimination leading to the corresponding 3,4‐dien‐1‐ol. If 3‐chloro‐2‐methyl‐4,5‐dihydrofuran serves as a substrate, however, no 3‐chloro‐3,4‐dien‐1‐ol can be isolated though it acts as a reaction intermediate. Its formation is slow compared to subsequent replacement of halogen by the organic moiety of the alkyllithium reagent. Thus penta‐3,4‐dien‐1‐ols are formed, which may isomerize, however, under certain reaction conditions affording terminal acetylenes. These as well as their allene precursors can be converted with sodium in ammonia into pent‐4‐en‐1‐ol or, respectively, pent‐3‐en‐1‐ol derivates.