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γ-内酯可由γ-羟基酸或α/β-烯酸分子内酯化制得,也可由丙烯酸酯和醇经自由基重排成环;或先合成2-烷基环戊酮,再经氧化成γ-内酯。它是常用香料。上文报导了用庚醛和丙二酸在三乙胺催化下合成了壬烯酸后者经分子筛催化成环制得γ-壬内酯。合成过程中发现,三乙胺催化所得的壬烯酸,环化能较快地进行。而且吡啶为催化剂所得的壬烯酸,环化速度则慢得多,得率也低。Boxer等曾用丁醛和丙二酸,用过量吡啶为催化剂合成了α-已烯酸,并估算出其中β-烯酸的含量约为2～5%。他们改用过量三乙醇胺为
γ-lactone can be γ-hydroxy acid or α / β-enoic acid molecular lactonization obtained, but also by the acrylate and alcohol rearranged into a ring by free radicals; Or first synthesis of 2-alkylcyclopentanone, and then by Oxidation to γ-lactone. It is commonly used spices. The report above reports the synthesis of nonenoic acid catalyzed by heptanal and malonic acid with triethylamine. The latter is cyclized into γ-nonanolactone by molecular sieve. During the synthesis, it was found that the nonenoic acid catalyzed by triethylamine could be cyclized faster. And pyridine as a catalyst of nonenoic acid, the cyclization rate is much slower, the yield is also low. Boxer et al. Used butyraldehyde and malonic acid, and synthesized a-hexenoic acid with an excess of pyridine as a catalyst and estimated that the content of β-enoic acid is about 2 to 5%. They switched to triethanolamine excess