Synthesis of Furo[3,4-<i>c</i>]furans Using a Rhodium(II)-Catalyzed Cyclization/Diels−Alder Cycloaddition Sequence
作者:Albert Padwa、Christopher S. Straub
DOI:10.1021/jo020413d
日期:2003.1.1
acetate, afforded furo[3,4-c]furans in good yield. The reaction proceeds by addition of a rhodium-stabilized carbenoid onto the acetylenic pi-bond to give a vinyl carbenoid that subsequently cyclizes onto the neighboring carbonyl group to produce the furan ring. These furo[3,4-c]furans react with various dienophiles, furnishing anisole derivatives derived by loss of water from the initially formed Diels-Alder
当用催化量的乙酸铑(II)处理时,一系列的2-炔基2-重氮-3-氧代丁酸酯,以良好的产率提供了呋喃[3,4-c]呋喃。通过将铑稳定的类胡萝卜素加到炔属π-键上来进行反应,得到乙烯基类胡萝卜素,其随后环化到相邻的羰基上以产生呋喃环。这些呋喃[3,4-c]呋喃与各种亲二烯体反应,提供了苯甲醚衍生物,该苯甲醚衍生物是由最初形成的Diels-Alder环加合物失去水而得的。就相互作用的羰基的性质而言,Rh(II)催化的环化反应非常灵活。通过首先生成2-烷氧基取代的呋喃,然后使其随后进行分子内Diels-Alder环加成反应,将该方法应用于几种氧杂多杂环系统的合成。所得环加合物的开环后,进行去质子化以提供重排的酮内酯。使用合适的模型重氮化合物探查了该方法在生物碱士的宁合成中的潜在用途。为了确定该方法的可行性,研究了Rh(II)催化的α-重氮酰胺64和68的环化/环加成序列。两种化合物均以良好的总收率