A short and efficient synthesis of a diterpenoid with a 1,2-seco-cladiellane carbon skeleton is described, starting from geraniol and carvone. One-step oxidative cyclization with a RuO2/NaIO4 system leads to two diastereomeric, bicyclic triols, which contain six stereogenic centers and will be helpful in the synthesis of eleutherobin. The stereochemical outcome of this cyclization has been determined
A Highly Efficient Procedure for Ruthenium Tetroxide Catalyzed Oxidative Cyclizations of 1,5-Dienes
作者:Stefanie Roth、Sabrina Göhler、Huan Cheng、Christian B. W. Stark
DOI:10.1002/ejoc.200500052
日期:2005.10
for the oxidative cyclization of 1,5-dienes, which generally allows for high yields and selectivities. A solid-supported terminal oxidant and a finely tuned solvent mixture have both been identified as critical factors for this high efficiency. As little as 0.2 mol-% ruthenium(III) chloride as a pre-catalyst for the rutheniumtetroxide generated in situ is required to accomplish oxidative cyclization
stereoselectively by syn oxygen addition to both double bonds. The formation of tetrahydrofuran derivatives is presumed to involve initial addition of RuO4 to one double bond of the 1,5-diene to give a ruthenium(VI) diester, which subsequently undergoes conversion into the cyclic ether with participation of the second double bond.
使用0.05当量的四氧化钌催化氧化1,5-二烯的改进方法。催化剂RuO 2 ·2H 2 O的当量,2.5当量。介绍了作为化学计量氧化剂的NaIO 4和AcOEt /(CH 3)2 CO / H 2 O(2:1:1,v / v / v)的双相溶剂体系。的1,5-二烯反应1,3,及5提供的新顺式-四氢呋喃产品2,4,6,和7具有完全的立体定向性。产品的结构是根据NMR和MS数据以及化学证据确定的。此过程以香叶基乙酸酯(中的应用8)和乙酸橙花酯(12得到)的顺式-四氢呋喃衍生物9,10,和13以高收率,并伴有少量的反式-tetrahydrofurandiols 11和14。这些产品与Sharpless等人获得的产品相同。RuO 4催化双相溶剂体系CCl 4中8和12的氧化/ CH 3 CN / H 2 O(2:2:3,v / v / v),但我们的方法具有立体特异性更高,材料回收率更高(约90%)和后处理更简单的优点。的1
Oxidative cyclization of 5,6-dihydroxyalkenes promoted by Cr(VI) oxo species: A novel cis-2,5-disubstituted tetrahydrofuran synthesis
作者:David M. Walba、George S. Stoudt
DOI:10.1016/s0040-4039(00)86932-4
日期:1982.1
Oxidative cyclization of isomeric 5,6-dihydroxyalkenes of type derived from neryl and geranyl acetates with Cr(VI) oxo species afford cis-THF diols of type (syn addition across the double bond) with >99.5% stereospecificity.