Highly stereoselective synthesis of perhydropyrano[2,3-b]pyrans from the new 3-methylidenepentane-1,5-dianion synthon
作者:Francisco Alonso、Jaisiel Meléndez、Miguel Yus
DOI:10.1016/j.tet.2006.03.011
日期:2006.5
is a new 3-methylidenepentane-1,5-dianion synthon which on reaction with an excess of lithium powder and a catalytic amount of DTBB (2.5%) in the presence of a carbonyl compound in THF at 0 °C, leads, after hydrolysis, to the expected methylidenic diols 3. These diols when subjected to successive hydroboration–oxidation and final oxidation, undergo spontaneous cyclisation to furnish a series of cis-perhydropyrano[2
4-苯基硫烷基-2-(2-苯基硫烷基乙基)丁-1-烯(2)是一种新的3-亚甲基戊烷-1,5-二价阴离子合成子,与过量的锂粉和催化量的DTBB(2.5% )在羰基化合物的存在下,在0°C的THF中,水解后会生成预期的亚甲基二醇3。这些二醇经过连续的硼氢化-氧化和最终氧化后,会自发环化,以高度非对映选择性的方式(> 99%de)提供一系列顺式-全氢吡喃并[2,3- b ]吡喃(4)。顺式-全氢吡喃并[2,3- b ]吡喃的酸催化异构化反应(4)也立体选择性地导致相应的反式-全氢吡喃并[2,3- b ]吡喃(5)。还包括有关4和5稳定性的讨论。