5-烷氧基-3,4-二卤-2(5H)-呋喃酮与不饱和胺的反应研究

为了深入探索5-烷氧基-3,4-二卤-2(5H)-呋喃酮与胺类试剂发生的反应,进一步在氟化钾作催化剂和四氢呋喃作溶剂的条件下,研究了其与系列不饱和胺的反应,通过旋光度,UV-Vis,IR,1H NMR,13C NMR,MS,元素分析和X射线单晶衍射等表征方法对产物进行结构表征,发现大多数情况下发生预期的串联迈克尔加成-消除反应,得到了16个新的β-胺基-2(5H)-呋喃酮化合物.当不饱和胺为空间位阻较大的2,5-二甲基-3-吡咯啉时,与位阻较大的5-孟氧基-3,4-二卤-2(5H)-呋喃酮反应只是生成异常的2(5H)-呋喃酮开环产物,而与位阻较小的5-甲氧基-3,4-二卤-2(5H)-呋喃酮反应则既有正常的β-胺基-2(5H)-呋喃酮产物,也有经开环重排反应的机理得到的异构体产物.后者表明,底物的位阻大小也是影响反应的因素,甚至导致同时存在竞争反应.

Researches on the Reaction of 5-Alkoxy-3,4-dihalo-2(5H)-furanones with Unsaturated Amines

In order to further explore the reactions of 5-alkoxy-3,4-dihalo-2(5H)-furanone with amines,the reactions with a series of unsaturated amines were investigated using KF as catalyst and THF as solvent.Sixteen new β-amino-2(5H)-furanone products were obtained via the tandem Michael addition-elimination reaction as anticipated in most cases,and their chemical structures and absolute configurations were confirmed via rotation,UV-Vis,IR,1H NMR,13C NMR,MS,elemental analysis and X-ray single crystal diffraction.However,the reaction between 2,5-dimethyl-3-pyrroline and 5-menthoxy-3,4-dihalo-2(5H)-furanones with larger steric hindrance just yielded unexpected 2(5H)-furanone ring-opening products,while 5-methoxy-3,4-dihalo-2(5H)-furanones with smaller steric hindrance gave both expected β-amino-2(5H)-furanones and unex-pected isomers involving the ring-opening rearrangement mechanism.The latter indicated that the steric hindrance of sub-strates could affect the reactions and even cause competitive reaction.