γ-内酯类化合物的合成

γ-内酯是一类重要的香料化合物。研究了以廉价易得的糠醛为原料制备γ-内酯的合成路线。以糠醛和1-溴丙烷、1-溴丁烷、1-溴己烷为起始原料,合成了γ-辛内酯、γ-壬内酯以及γ-十一内酯。糠醛首先与溴代烷的格氏试剂在乙醚中反应,生成1-(2-呋喃基)烷醇,反应产率在86%左右。1-(2-呋喃基)烷醇在质量分数为0.5%的氯化氢的乙醇溶液中回流,开环水解得4-氧代羧酸,反应产率在60%左右。4-氧代羧酸与氯化亚砜在甲醇中回流反应,得4-氧代羧酸甲酯,产率约93%。4-氧代羧酸甲酯用硼氢化钠在甲醇中室温搅拌2 h,还原并且同时关环得γ-内酯,产率约85%。

Syntheses of γ-Lactones

γ-Lactones are very important flavor compounds.A series of γ-lactones,including γ-octanoic lactone and γ-nonanoic lactone and γ-undecanoic lactone,were synthesized by using cheap furfural and 1-bromopropane,1-bromobutane and 1-bromohexane as starting materials.The reactions of furfural with Grignard reagents of the bromoalkanes in ether gave 1-(2-furanyl) alkanols in c.a.86% yields.4-Oxocarboxylic acids were obtained in c.a.60% yields by the hydrolysis of 1-(2-furanyl) alkanols in w(HCl)=0.5% ethanol solution under reflux.4-Oxocarboxylic acids reacted with SOCl2 in methanol under reflux to give methyl 4-oxocarboxylates in c.a.93% yields.Methyl 4-oxocarboxylates were reduced with NaBH4 in methanol at room temperature,and cyclized concurrently to form γ-lactones in c.a.85% yields.