Development of New Radical Acceptors and Their Application to Organic Synthesis

本项目的目的是开发具有硫官能团的烯烃作为新的自由基受体。重点研究了乙烯酮二硫代缩醛S、S-二氧化物和乙烯基砜，得到了以下结果.烯酮二硫缩醛S，S-二氧化物被发现是一个有效的自由基受体。特别地，1-羟烷基和1-烷氧基烷基以高效率加成到烯酮二硫代缩醛S，S-二氧化物中。与相应的乙烯基砜相比，它们具有更高的接受己基自由基（4倍）或2-羟基-2-丙基自由基（2.4倍）的能力.在自由基引发剂（AIBN）存在下，在乙苯中，用氢化三丁基锡处理在ω-位上具有卤素原子的烯酮二硫代缩醛S，S-二氧化物，得到分子内环化产物。值得注意的是，高度应变的环丁烷衍生物可以在约100 ° C下形成。50%的收益率。这归因于通过硫基和磺酰基的组合稳定中间环化自由基（捕获效应）。含催化量AIBN的乙烯基砜醇溶液经辐照或加热后，可通过自由基链反应机理高产率地生成1-羟烷基加合物.该加合物是由乙烯酮二硫缩醛S，S-二氧化物和一个自由基形成的，它可以通过与卤代烷和碱（NaH或丁基锂）的烷基化反应，然后酸水解得到相应的酮。

The purpose of this project was to develop the alkenes having sulfur functionalities as new radical acceptors. Especially our attention was paid on ketene dithioacetal S,S-dioxides and vinyl sulfones, and the following results were attained.1. Ketene dithioacetal S,S-dioxides were found to be an efficient acceptor of radicals. In particular, 1-Hydroxyalkyl radicals, and 1- alkoxyalkyl radicals added to the ketene dithioacetal S,S-dioxides with a high efficiency. In comparison with the corresponding vinyl sulfones, they exhibited higher ability to accept hexyl radical (4 times) or 2- hydroxy-2-propyl radical (2.4 times).2. When ketene dithioacetal S,S-dioxides having a halogen atom at the omega- position was treated with tributyltin hydride in the presence of a radical initiator (AIBN) in refluxing benzene, an intramolecularly cyclized product was obtained. It is noteworthy that a highly strained cyclobutane derivative can be formed in ca. 50% yield. This is attributable to the stabilization of an intermediary cyclization radical by a combination of thio and sulfonyl groups (captodative effect).3. On irradiation or heating of the alcoholic solution of a vinyl sulfone containing a catalytic amount of AIBN, a radical chain mechanism operates to give an adduct of 1-hydroxyalkyl radical in a high yield.4. The adduct, which was derived from a ketene dithioacetal S,S-dioxide and a radical, was found to afford the corresponding ketone by alkylation with an alkyl halide and a base (NaH or butyllithium) followed by acidic hydrolysis.