A protecting group Ph2P(O) for terminal ethyne was newly developed. This protecting group can be introduced readily to terminal ethyne by CuI-catalyzed phosphination and subsequent oxidation with H2O2. Ph2P(O)-protected ethynes remained intact in Sonogashira coupling, and their high polarity enabled easy separation of the desired coupling product from by-products. By treatment with t-BuOK, Ph2P(O)-protected
Regiospecific and stereoselective synthesis of (<i>E</i>)- and (<i>Z</i>)-2-phosphino-1-alkenyl boronates <i>via</i> Cu-catalyzed hydroboration of alkynylphosphines
stereoselective synthesis of (E)- and (Z)-2-phosphino-1-alkenyl boronates via Cu-catalyzed hydroboration of alkynylphosphines. A remarkable ligand-controlled stereoselectivity in the transformation is presented. The study on the coordination chemistry of the new phosphine/borane compounds with gold suggests the presence of very weak Au → B interaction in the gold complex 4 ligated by (E)-2-phosphino-1-alkenyl
Six-coordinate [trans-RuCl2(PPh2C equivalent to CR)(4)] (R = Ph (1), (4-CH3)C6H4 (2), (4-OCH3)C6H4, (3), (4CF(3))C6H4 (4)) were obtained from the reaction of RuCl3 center dot xH(2)O with the appropriate alkynylphosphine (PPh2C equivalent to CR) in ethanol. An X-ray crystal structure analysis of 1 center dot 4H(2)O reveals that the complex is obtained as the trans isomer, with the halides occupying apical positions and the phosphorus atoms lying in the equatorial plane. The alkynyl substituents of adjacent P ligands are alternatively pointing up and down and are maintained within the vertical plane by a set of weak hydrogen interactions [intra C-H... Cl and C-H center dot center dot center dot pi(C equivalent to CPh)] connecting the ortho-H of the phenyl rings with the chloride and acetylenic moieties, respectively. Complexes 1 and 2 react cleanly with phenylacetylene via dissociative loss of one alkynyphosphine ligand to yield saturated 18 e(-) Ru(II) vinylidene complexes [mer,cis-RuCl2(C=CHPh)(PPh2C equivalent to CR)(3)] (R = Ph (12), Tol (13)). The catalytic activity of 1-4 in ROMP reactions of norbornene and several functionalized norbornenes in the presence of trimethylsilyldiazomethane (TMSD) as the carbene source is also described.