Synthesis of Polyfunctionalyzed Molecules Using Cooperative Interactions between Multiple Elements

在α或β碳原子上带有PhSe基团的端炔（1）含有三个反应活性中心（C-C三键、端炔氢原子、PhSe基团）。通常，末端炔的加氢金属化立体特异性地发生以得到E-烯属金属物质，其被一些亲电试剂如醛、环氧化物和酰卤取代以构建新的碳-碳键。另一方面，有机硒化学近年来成为有机合成中非常有力的工具。特别重要的是，由于其易于处理的性质。1与锆茂-乙烯络合物反应，区域选择性地得到锆环戊烯衍生物。1与Cp_2ZrHCl的锆氢化反应和与Me_2Zn的金属转移反应，区域和立体选择性地得到相应的末端乙烯基锌中间体，再与醛发生偶联反应，得到含苯硒基的烯丙醇衍生物。在-78 ℃下，1的末端氢原子容易被n-BuLi夺取，生成sp碳负离子物种，这些物种被醛有效地捕获在环氧化物上。用过量的H_2O_2氧化含苯硒基的化合物，通过硒醚顺式消除反应，以较好的产率得到含A型烯醇结构的产物，苯硒醇酯与二茂钛（Cp_2TiMe_2）发生亚甲基化反应，得到烯基硒醚，再用m-CPBA氧化，通过硒醚顺式消除反应，得到端炔而不是丙二烯。另一方面，α-苯硒酮与Cp_2TiMe_2反应生成烯丙基硒醚的混合物，随后被H_2O_2氧化，通过[2，3] σ转移重排生成烯丙基醇。

Terminal alkynes (1) having a PhSe group on α or β carbonn atom contain three reactive sites (C-C triple bond, terminal alkynic hydrogen atom, PhSe group). Generally, hydrometalation of terminal alkynes takes place stereospecifically to give the E-alkenic metal species which are replaced by some electrophiles such as aldehydes, epoxides, and acyl halides to construct a new carbon-carbon bond. On the other hand, organoselenium chemistry became a very powerful tool in organic synthesis in recent times. Of particular importance is the owing to its easily handled nature.1 reacted with zirconocene-ethylene complex to give regioselectively zirconacyclopentene derivatives. Hydrozirconation of 1 with Cp_2ZrHCl followed by transmetalation with Me_2Zn gave the corresponding terminal vinylzinc intermediates regio-and stereoselectively, which underwent the coupling reaction with aldehydes to afford the allylic alcohol derivatives having a phenylseleno group. Terminal hydrogen atom of 1 was easily abstracted by n-BuLi at-78℃ to generate sp carbanion species which were effectively trapped by aldehydes on epoxides. The compounds with a phenylseleno group were oxidized with excess amounts of H_2O_2 to yield the desired products having A-shaped olefinic alcohol moiety in good yields via selenoxide syn elimination.Methylenation of phenylselenolesters with dimethyl titanocene (Cp_2TiMe_2) gave alkenyl selenides, which were subjected to oxidation with m-CPBA to afford terminal alkynes, not to allene, via selenoxide syn elimination. On the other hand, reaction of α-phenylseleno ketones with Cp_2TiMe_2 gave a mixture of isomeric allylic selenides and the subsequent oxidation by H_2O_2 led to the formation of allylic alcohols via [2,3] sigmatropic rearrangement.