Fu Zhenqian, Wang Mang, Ma Yuhui, Liu Qun, Liu Jun
Department of Chemistry, Northeast Normal University, Changchun, 130024, People's Republic of China.
J Org Chem. 2008 Oct 3;73(19):7625-30. doi: 10.1021/jo801406p. Epub 2008 Aug 30.
A route to 2,3,4-trisubstituted furan derivatives based on a [3 + 2] annulation of functionalized allylic sulfoxides and aldehydes is described. In this strategy, the precursors of allylic sulfoxides 4, allylic sulfides 3, were synthesized via a thiomethylation reaction of an alpha-EWG ketene-S,S-acetal 1 (EWG: electron-withdrawing group), formaldehyde, and a thiol 2 in high to excellent yields. Allylic sulfoxides 4 were prepared by a highly regioselective oxidation of 3, using m-chloroperoxybenzoic acid as oxidant. Thus, starting from these readily available sulfoxides 4, 2-alkylthio-3,4-disubstituted furans 6 were efficiently constructed via the [3 + 2] annulation reaction of 4 with aldehydes 5 under mild conditions. Further replacement of the 2-alkylthio group of 6 with amines led to the formation of 2-amino-3,4-disubstituted furan derivatives 7.
描述了一种基于官能化烯丙基亚砜与醛的[3 + 2]环化反应合成2,3,4-三取代呋喃衍生物的方法。在该策略中，烯丙基亚砜4的前体烯丙基硫醚3是通过α-吸电子基团的乙烯酮-S,S-乙缩醛1（EWG：吸电子基团）、甲醛和硫醇2的硫甲基化反应以高至优异的产率合成的。烯丙基亚砜4是通过使用间氯过氧苯甲酸作为氧化剂对3进行高度区域选择性氧化制备的。因此，从这些容易获得的亚砜4开始，在温和条件下通过4与醛5的[3 + 2]环化反应有效地构建了2-烷硫基-3,4-二取代呋喃6。用胺进一步取代6的2-烷硫基导致形成2-氨基-3,4-二取代呋喃衍生物7。
