Development of Efficient Molecular Transformations Using Metal and Heteroatom Compounds

点击翻译按钮获取中文摘要

Terminal alkynes having a PhSe group on a or β carbon atom contain some reactive sites (C-C triple bond, acidic protons, phenylseleno group) and has potential as a synthetic precursor to highly functionalized compounds. Hydrozirconation of homopropargyl phenyl selenide (1)with Schwartz's reagent gave the corresponding terminal vinylzirconocene regio-and stereoselectively. This zirconocene intermediate was successively subjected to Stille-type coupling with aryl or alkenyl iodides in the presence of Pd(0) catalyst, followed by oxidative removal of the phenylseleno group via selenoxide syn elimination to afford conjugated polyene compounds with E-configuration in good yields. Phenyl propargyl selenide (2)was easily deprotonated by 2 equiv of LDA in THF at -78℃ to give a solution of the dianion reagent. Aldehydes reacted with the dianion exclusively at the a position of selenium atom to afford homopropargyl alcohol derivatives. Oxidation of these compounds with 1 equiv of m-CPBA gave the … More corresponding selenoxides, which underwent the [2,3] sigmatropic rearrangment to yield α-phenylseleno-substituted enone derivatives, presumably via allenyl alcohol intermediates. E-isomers of enone compounds were followed by cyclization via an intramolecular hemiacetalization to give 2-hydroxy-2,5-dihydrofuran derivatives. Interestingly, the addition of pyridine to the reaction mixture led to an exclusive formation of the dihydrofuran compounds. Thus, the dianion of 2 served as a synthetic equivalent of acrolein dianion, and the two anionic centers can be utilized separately. The similar oxidation of silylated propargyl selenide derivatives resulted in the formation of α,β-unsaturated acylsilanes in good yields. Silylated homopropargyl alcohol derivatives were oxidized by m-CPBA to give 2-silyl-3-phenylselenofuran compounds and γ-hydroxy-substituted Z-α,β-unsaturated acylsilanes. The former may be obtained via an intramolecular cyclization of the corresponding E-α,β-unsaturated acylsilanes followed by the dehydration. Less