New Method of Radical Formation and Its Application to Organic Synthesis

一种新的生成有机自由基物种的有效方法已被应用于有机合成。三乙基硼烷引发的三苯基锡烷与乙炔的加成反应在高区域和立体选择性下顺利进行。应用于在适当位置含有烯键的乙炔，立体选择性地提供环化产物；三苯基锡自由基区域选择性地攻击乙炔键，得到乙烯基，其在分子内立体选择性地加成到烯烃上。三苯基锗在三乙基硼烷催化下加成1-炔烃。在这种情况下，反应在-78ﾟC下进行动力学控制，得到Z-异构体，而在60ﾟC下进行热力学控制，得到主要的异构体。通过对上述反应的机理研究，设计出了一种有效的烯烃几何构型异构化反应过程。烷基卤化物可通过自由基型还原还原为相应的碳氢化合物。烷氧基硫代羰基的分子内加成反应是一种相当于酰基的自由基，可得到亚甲基内酯。烷基碘在三乙基硼烷催化下顺利地与乙炔反应生成区域选择性和立体选择性的碘乙烯基化合物。全氟烷基碘以类似的方式加到乙炔上。在三乙基硼烷存在下，AN-溴代酮与羰基化合物反应生成Reformsky类型的反应产物；生成硼烯醇酸并与醛反应生成羟醛产物。三乙基硼烷催化的烷基碘与甲基乙烯基酮的加成反应也得到了硼烯醇酸。当所得的硼烯醇酸与醛反应生成羟醛产物时，上述反应开启了烷基碘、甲基乙烯基酮和醛的三组分偶联反应。

Novel efficient method for the generation of organic radical species has been applied to organic syntheses. Triethylborane-initiated addition of triphenylstannane to acetylenes proceeds smoothly in high regio- and stereoselectivity. Application to an acetylene containing an olefinic bond at appropriate position provides a cyclized product stereoselectively; triphenyltin radical attacks at acetylene bond regioselectively to give a vinyl radical, which adds intramolecularly to an olefin stereoselectively. Triphenylgermane adds to a 1-alkyne under triethylborane catalysis. In this case, reaction is kinetically controlled at -78ﾟC to give Z-isomer, whereas reaction is thermodynamically controlled at 60ﾟC affording Enisomer predominantly. By the mechanistic investigation of the above reaction, an efficient procedure of the isomerization of olefin geometry has been devised. Alkyl halides can be reduced to the corresponding hydrocarbons by radical type reduction. Intramolecular addition of alkoxythiocarbonyl radical, an acyl radical equivalent, gives an -methylene lactone. Alkyl iodides add to acetylene smoothly under triethylborane catalysis to give vinyl iodides regio- and stereoselectively. Perfluoroalkyl iodides add to acetylenes analogously. Reaction of an -bromo ketone with a carbonyl compound in the presence of triethylborane gives a Reformatsky type reaction product; formation of boron enolate and reaction with aldehyde to give an aldol product. Triethylborane-mediated addition of an alkyl iodide to methyl vinyl ketone also gives a boron enolate. As the obtained boron enolate reacts with an aldehyde to give aldol product, the above reactions opens novel three components coupling reaction of alkyl iodide, methyl vinyl ketone, and aldehyde.