Ring Closure Reactions of Disubstituted 4-Penten-1-oxyl Radicals − Towards a Stereoselective Synthesis ofallo-Muscarine
作者:Jens Hartung、Rainer Kneuer
DOI:10.1002/(sici)1099-0690(200005)2000:9<1677::aid-ejoc1677>3.0.co;2-x
日期:2000.5
tetrahydrofurans was achieved by an efficient and highly regioselective alkoxyl radical cyclization (5-exo-trig). The 2,3-anti substituted intermediates 9 and 12 cyclize stereoselectively whereas a 2,3-syn-configured O-radical affords both possible diastereomeric addition products in equal amounts. The cyclized tetrahydrofuryl methyl radicals were trapped with the bromine atom donor BrCCl3 to afford the bromomethyl-substituted
三取代的官能四氢呋喃10,11,16,18,和19分别从光化学制备2,3-顺式-和2,3-反-型ñ - (3-苯甲酰基-5-己烯-2-氧基)噻唑-2- (3 ħ) -硫酮抗- 6,pyridinethiones 7,抗- 8,和BrCCl 3。四氢呋喃的形成通过有效且高度区域选择性的烷氧基自由基环化(5- exo -trig)实现。2,3-抗被取代的中间体9和12立体选择性地环化,而2,3-顺式构型的O-自由基提供相等量的两种可能的非对映异构加成产物。该环化的四氢呋喃基甲基自由基被困与溴原子供体BrCCl 3,得到溴甲基取代的环醚10,11,18,和19以优良产率。-该反应的效用通过在两步合成为(+)的新制备的四氢呋喃中的一个的转换强调异体-muscarine(+) - 20。