A new 3-methylidenepentane-1,5-dianion synthon: synthesis of perhydropyrano[2,3-b]pyrans and 1,7-dioxaspiro[4.5]decanes
作者:Francisco Alonso、Jaisiel Meléndez、Miguel Yus
DOI:10.1016/j.tetlet.2005.07.077
日期:2005.9
4-Phenylslilfanyl-2-(2-phenylsulfanylethyl)but-1-ene (2) has proved to be an appropriate and new 3-methylidenepentanel-1,5-dianion synthon. The reaction of 2 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 degrees 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[2,3-b]pyrans (4) in a highly diastereoselective manner (>99% de). Additionally, diols 3 also undergo double intramolecular iodoetherification promoted by a silver salt, to furnish the corresponding 1,7-dioxaspiro[4.5]decanes (6) in very high yields. (c) 2005 Elsevier Ltd. All rights reserved.