The Synthesis of Internal Conjugated (E)-Enynyldialkylboranes and Their Applications to the Syntheses of Conjugated Alkynones, Conjugated (E)-Enynes, and Conjugated Enynes Bearing an Unsaturated Group on the Double Bond

Abstract

Abstract Internal conjugated (E)-enynyldialkylboranes were synthesized by successive reactions of 1-iodo-1-alkynes with dialkylboranes and 1-alkynyllithiums in 31–79% yields. (E)-Enynyldialkylboranes, thus obtained, gave regio- and/or stereospecifically defined corresponding conjugated alkynones by alkaline hydrogen peroxide oxidation, conjugated (E)-enynes by protonolysis with acetic acid, and conjugated enynes bearing an unsaturated group on the internal alkenyl carbon atom by bis(acetylacetonato)copper-catalyzed cross-coupling reaction with allyl bromide or 1-bromo-1-hexyne respectively.