Studies toward the Synthesis of α-Fluorinated Phosphonates via Tin-Mediated Cleavage of α-Fluoro-α-(pyrimidin-2-ylsulfonyl)alkylphosphonates. Intramolecular Cyclization of the α-Phosphonyl Radicals
作者:Stanislaw F. Wnuk、Luis A. Bergolla、Pedro I. Garcia
DOI:10.1021/jo0111560
日期:2002.5.1
sulfone moiety and an alternative route for the preparation of alpha-fluorinated phosphonates. Desulfonylation is suggested to proceed via attack of tin radical at an oxygen (or sulfur) atom of the sulfonyl group to give a stabilized alpha-phosphonyl radical intermediate. The latter was found to undergo 5-exo-trig ring closure to give the corresponding 2-methylcyclopentylphosphonates. Treatment of diethyl
用Selectfluor处理从几种α-(嘧啶-2-基磺酰基)烷基膦酸酯生成的α碳负离子,可高产率地生产出α-氟-α-(嘧啶-2-基磺酰基)烷基膦酸酯,将其磺酰化[Bu(3)SnH / 2,2'-偶氮二异丁腈(AIBN)/苯或甲苯/δ]得到α-氟代烷基膦酸酯。在氟化钾的存在下,由氯化三丁基锡和过量的聚甲基氢硅氧烷生成的“催化”氢化锡,也从膦酸酯中除去了π-不足的α-(嘧啶-2-基磺酰基)基团。用Bu(3)SnD代替Bu(3)SnH可以访问α-氘标记的膦酸酯。用过量的Bu(3)SnH / AIBN或催化氢化锡长时间处理α-(吡啶-2-基磺酰基)烷基膦酸酯也可实现脱磺酰化,但收率中等。这代表了一种温和的新方法,用于去除合成上有用的pi不足的杂环砜部分,以及制备α-氟化膦酸酯的替代途径。建议通过在磺酰基的氧(或硫)原子上锡基的侵蚀进行脱磺酰化,以得到稳定的α-膦酰基自由基中间体。发现后者进行5-e