Development of Novel Activation Methods of Metals and its Applicatoin to Organic Synthesis.

金属表面覆盖着薄而紧密结合的氧化层。为了将这类金属用于有机合成，必须开发有效的去除氧化层的方法。用Me_3SiCl处理可以有效地去除金属锰表面的金属氧化层，而催化量的PbCl2对金属锰具有惊人的活化作用。用活化的金属锰进行重排反应和羰基化合物的烯丙化反应。在此条件下，利用锰还原体系，烷基碘、α、β-不饱和腈(或酯)和羰基化合物的三组分偶联反应可以很好到很好地实现。虽然PbCl2的作用尚不清楚，但添加催化量的盐对于还原烷基碘是必不可少的。烷基自由基以1，4-方式加到烯丙基丙烯酸酯中，得到α-烯丙氧羰基取代的烷基自由基，经单电子还原后生成烯丙基硅基缩醛…更多的氮和Me_3SiCl的捕获。在DMF和THF中，1，4-加成反应和连续的爱尔兰-克莱森重排反应是通过烷基碘和锰-PbCl2-Me_3SiCl体系进行的。从爱尔兰-克莱森重排生成的双键具有预期的E几何构型。上述顺序反应是通过区分烷基和α-烷氧基羰基取代的芳基的中等锰还原体系实现的。下面的立体选择性有机转化也是用低价铬进行的。(1)以二氯甲基硼酸酯、CrCl2和LiI为原料，在温和的条件下，以醛为原料，经碳烯烃扩链反应，合成了合成有用的(E)-1-烯基硼酸酯。(2)根据镍(II)盐的催化量，考察了以前报道的炔基和烯基铬试剂的制备方法，建立了制备铬试剂的标准方案。较少

Metals are covered with thin but tightly bound oxide layrs on its surface. In order to employ such metals in organic synthesis, efficient methods for removing the oxide layrs should be developed.Metal-oxide layrs of manganese metal surface is effectively removed by treatment with Me_3SiCl, and a catalytic amount of PbCl_2 activates the manganese metal amazingly. Reformatsky-type reaction and allylation of carbonyl compounds are performed with the activated manganese metal. In sddition, three-component coupling reactions of alkyl iodides, alpha, beta-unsaturated nitriles (or esters), and carbonyl compounds are achieved in good to excellent yields with the manganese reducing system. Although the role of PbCl_2 is unclear, addition of a catalytic amount of the salt is essential for reducing the alkyl iodide.Addition of alkyl radicals to allylic acrylates in a 1,4-fashion gives alpha-allyloxycarbonyl-substituted alkyl radicals, which produce ketene silyl acetals after one-electron reductio … More n and trapping with Me_3SiCl. The 1,4-addition and successive Ireland-Claisen rearrangement take place by using alkyl iodides and the manganese-PbCl_2-Me_3SiCl system in DMF and THF.The double bond produced has E geometry as expected from the Ireland-Claisen rearrangement.The above sequential reactions are realized by using the moderate manganese reducing system which discriminate between alkyl and alpha-alkoxycarbonyl-substituted alyl radicals.The following stereoselective organic transformations have also been developed with low-valent chromium. (1) Synthetically useful (E) -1-alkenylboronic esters are prepared stereoselectively from aldehydes with olne-carbon extention by using a geminal dichromium reagent derived from a dichloromethylboronic ester, CrCl_2, and LiI under mild conditions. (2) By examination of the previously reported preparative methods of alkynyl- and alkenylchromium reagents in terms of a catalytic amount of nickel (II) salt, standard protocols for perparation of the chromium reagents are established. Less