Synthesis of Polyfunctionalyzed Molecules Using Cooperative Interactions between Multiple Elements

在α或β碳原子上具有PHSE基团的末端炔烃(1)含有三个反应中心(C-C三键、末端烯烃氢原子、PHSE基团)。通常情况下，末端炔烃的氢金属化反应是立体地进行的，以生成E-烷基金属物种，这些金属物种被一些亲电性物质如醛、环氧化物和酰基卤化物所取代，从而形成新的碳-碳键。另一方面，近年来，有机硒化学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与茂锆烯-乙烯络合物反应，得到区域选择性的茂锆环戊烯衍生物。1与Cp_2ZrHCl氢锆化，然后与Me_2ZN转金属化得到相应的末端乙烯基锌中间体，这些中间体与醛发生偶联反应，得到含苯基硒的烯丙醇衍生物。在-78℃下，1的末端氢原子很容易被n-BuLi抽提生成固相碳负离子物种，并被环氧化物上的醛有效捕获。以过量的H_2O_2氧化含有苯基硒的化合物，以较高的产率得到具有A型烯醇部分的产物。苯基硒与钛并二茂二甲酯(Cp_2TiMe_2)的亚甲基化得到烯基硒，再用间CPBA氧化得到端炔，而不是烯。另一方面，α-苯基硒基酮与Cp_2TiMe_2反应生成烯丙基硒的混合物，然后被H_2O_2氧化生成烯丙基醇。

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.