Synthesis of exo enol ether-cyclic ketal isomers of substituted furanmethanol structures related to marine furanocembranoids
作者:Yi Li、Gerald Pattenden、Joseph Rogers
DOI:10.1016/j.tetlet.2009.12.131
日期:2010.3
of the epoxide 10 with p-TSA in MeOH produces the enol ether cyclic ketal 12, which is rapidly isomerised to the furanmethanol ether 15, isolated in 80% yield. By contrast, when the propanol-substituted furan epoxide 23 was kept in CDCl3 containing traces of HCl for 2 h, a 3:2 mixture of Z- and E-isomers of the enol ether spiro ketals 25a and 25b was produced in >92% yield; after 24 h this mixture of
使用过氧试剂氧化2-烯基呋喃8a和8b分别导致二烯二酮9和呋喃环氧化物10。用对-TSA的MeOH溶液处理环氧化物10,产生烯醇醚环状缩酮12,其迅速异构化为呋喃甲醇醚15,以80%的收率分离。相反,当将丙醇取代的呋喃环氧化物23在含有痕量HCl的CDCl 3中保持2小时时,烯醇醚螺缩酮25a和25b的Z和E异构体的3:2混合物产量> 92%;24小时后,使该异构体混合物脱水,得到相应的烯醇醚三烯26(70%)。当将二烯二酮9在含有p -TSA的H 2 O-THF中的溶液在25°C下搅拌20 h时,会生成叔醇27,再经过20 h转化为呋喃邻位二醇29。同样地,当'西松' dienedione 31中的溶液用p -tsa-H 2 O,羟甲基取代的furanobutenolide 33是在40%的产率生产。烯醇醚环状半缩酮28和32 / 34,这是与12和25,并且也与天然存在的cembranoids