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    Oligosaccharide analogues of polysaccharides. Part 21. Towards new cellulose I mimics: Synthesis of dialkynyl C-glucosides of peri-substituted anthraquinone
    (2001) Sl M.; Venanzi L.M.
    The bis-C-glucoside 2 has been synthesised as the first representative of a series of templated glucosides and cellooligosaccharides that mimick part of the unit cell of cellulose I. As expected, there are, at best, weakly persistent H-bonds between the two glucosyl residues in (D 6)DMSO and (D 7)DMF solution. The acetylated oct-1-ynitol 7 and deca-1,3-diynitol 12 were prepared from the gluconolactone 5 (Scheme 1). Coupling of 12 to Phi and 2-iodothiophene yielded 13 and 14, respectively, while dimerisation of the benzylated and acetylated deca-1,3-diynitols 10 and 12 afforded the bis-C-glucosyloctatetrayne 15 and the less stable 16, respectively. The 2-glucosylthiophene 17 was obtained by treating the C-silylated deca-1,3-diynitol 9 with Na 2S. Cross-coupling of (trimethylsilyl)acetylene (TMSA) with 1,8-bis(triflyloxy)-9,10-anthraquinone (20) at elevated temperature gave the dialkynylated 21; its structure was established by X-ray analysis (Scheme 2). Sequential coupling of 6 or 7 and TMSA to 20 gave the symmetric dialkyne 21, the mixed dialkynes 23 (from 6) and 25 (from 7), and the symmetric diglucoside 36 (from 7) in modest yields; a stepwise coupling to the acetylated monotriflate 28 proved advantageous. It led to the oct-1-ynitol 29 and the deca-1,3-diynitol 33 that were transformed into the triflates 30 and 34, respectively. Coupling of the triflate 34 to the oct-1-ynitol 7 gave the unsymmetric bis-C-glucoside 35; this was obtained in higher yields by coupling the triflate 30 to the deca-1,3-diynitol 12. Coupling of the bistriflate 20 with either 7 or 12 afforded the symmetric bis-C-glucosides 36 and 37, respectively. Deacetylation (KCN in MeOH) of 35-37 provided the unsymmetric bis-C-glucoside 2 and the symmetric analogues 3 and 4.
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    The synthesis of the tripodal phosphine CH3C{CH2P(m-CF3C6H4) 2}3 and its rhodium coordination chemistry
    (Elsevier S.A., 1998) Sülü M.; Venanzi L.M.; Gerfin T.; Gramlich V.
    The new tripodal phosphine CH3C{CH2P(m-CF3C6H4) 2}3, CF3PPP, was prepared by reacting CH3C(CH2Br)3 with Li+P(m-CF3C6H4)2 -, the latter being best obtained by adding Li+NiPr2- to PH(m-CF3C6H4)2. The rhodium complexes [RhCl(CO)(CF3PPP)], [Rh(LL)(CF3PPP)](CF3SO3) (LL=2 CO or NBD), [RhX3(CF3PPP)], [RhX(MeCN)2(CF3PPP)](CF3SO3) 2 (X=H and Cl), [RhCl2(MeCN)(CF3PPP)](CF3SO3) and [Rh(MeCN)3(CF3PPP)](CF3SO3) 3 were prepared and characterized. The X-ray crystal structure of [Rh(NBD)(CF3PPP)](CF3SO3) is reported. The lower oxygen sensitivity of the CF3PPP rhodium(I) complexes, relative to the corresponding species with the parent ligand CH3C(CH2PPh2)3, is attributed to the higher effective nuclear charge on the metal centers caused by the presence of the six CF3 substituents on the terdentate phosphine. A similar effect may be responsible for the easier hydrolysis of the CF3PPP-containing, cationic rhodium(III) complexes relative to the corresponding compounds of the parent ligand. © 1998 Elsevier Science S.A.