3-acyl-2-alkyl-4,5-dihydrofurans. Similar cyclization of α-acyl-α,β-unsaturated esters initially afforded 3-alkoxycarbonyl-2-alkyl-4,5-dihydrofurans which were transformed into 2-acylbutanolides on further reaction with sulfuric acid.
用
硫酸或二甲基甲酰胺-
氯化氢或
对甲苯磺酸处理α-酰基-α,β-不饱和酮产生3-酰基-2-烷基-4,5-二氢
呋喃。类似地环化α-酰基-α,β-不饱和酯,最初得到3-烷氧基羰基-2-烷基-4,5-二氢
呋喃,将其在进一步与
硫酸反应后转化为2-酰基
丁醇化物。