Scandium perchlorate

In the presence of scandium perchlorate, 2,6-diacetylpyridine condenses with m-phenylenedia-mine to form a macrocyclic complex ScL(C104)3 4H20 (L is shown as (4)). The structure has not been determined, but the perchlorates are not coordinated. " The reaction probably proceeds via the (isolable) complex Sc(diacetylpyridine)2(C104)3 7H20. 

Furanoid Compounds.—As has become usual, a range of methods have been applied to the synthesis of compounds of this series. Scandium perchlorate, an unusual Lewis acid catalyst, catalysed the reaction of 2,3,5-tri-O-benzoyl-P-D-ribopyranosyl acetate and a-(trimethylsilyloxy)styrene to give the benzoylmethyl C-furanosides in very high yield with 94 6 selectivity in favour of the a-anomer. In parallel work the analogous benzylated ribofuranosyl... 

These reactions are presumed to occur through aroyl triflate intermediates which dissociate to aiyl acylium ions. Lithium perchlorate and scandium triflate also promote acylation. ... 

Z 1 Niobium 1 Nitrate 1 Osmium 73 a. I Perchlorate Phenols u a o Platinum o 0. 1 5 u 1 Rhodium 1 Rubidium Ruthenium Scandium 1 Selenium Silver I Sodium 1 Strontium 1 Sulphate Sulphides, organic Sulphur dioxide 1 Tantalum 1 Tellurium 1 Thallium Thorium e H 1 Titanium a u ab a 1- I Uranium 1 Vanadium 1 Yttrium 1 Zinc Zirconium... 

In the Mukaiyama aldol additions of trimethyl-(l-phenyl-propenyloxy)-silane to give benzaldehyde and cinnamaldehyde catalyzed by 7 mol% supported scandium catalyst, a 1 1 mixture of diastereomers was obtained. Again, the dendritic catalyst could be recycled easily without any loss in performance. The scandium cross-linked dendritic material appeared to be an efficient catalyst for the Diels-Alder reaction between methyl vinyl ketone and cyclopentadiene. The Diels-Alder adduct was formed in dichloromethane at 0°C in 79% yield with an endo/exo ratio of 85 15. The material was also used as a Friedel-Crafts acylation catalyst (contain-ing7mol% scandium) for the formation of / -methoxyacetophenone (in a 73% yield) from anisole, acetic acid anhydride, and lithium perchlorate at 50°C in nitromethane. 

Elsewhere, Faita et al. (438) bound the Evans chiral auxiliary to Wang or Merrifield resin for use as a dipolarophile in cycloadditions with C,N-diphenyl-nitrone. Yields on both resins are significantly reduced in comparison to the solution phase reaction (43-20% compared to 95%) but are unaffected by addition of magnesium perchlorate or scandium triflate catalyst. A one-pot process has been reported by Hinzen and Ley (439) that oxidizes secondary hydroxylamines to the... 

The subsequent fate of the perchlorate depends on the temperature. At relatively low temperatures it is stable and thus remains. At temperatures high enough for it to decompose, the final products are chloride and oxygen. When the metal exists in more than one oxidation state, the oxide may form. The chlorates of the rare earths, scandium, and yttrium form oxychlorides. 

Grey anhydrous scandium triflate, [Sc(03SCF3)3] (triflate = trifluoromethane sulfonate), has been obtained by dehydration of the hydrate at 190 200 °C the hydrated salt was itself obtained from the reaction of hydrated scandium chloride and dilute triflic acid. [Sc(03SCF3)3], in which triflate is believed to act as a bidentate ligand (similar to perchlorate in 80(004)3), is not isomorphous with the lanthanide analogues. 

Other scandium perfluoroalkanesulfonates such as the pentafluoroethanesulfonate and nona-fluorobutanesulfonate have also been shown to be good catalysts.204 Scandium salts such as the perchlorate and alkylsulfates205 are also active catalysts. 

The complex formation between Sc and SeOj" was studied by measurement of the distribution of Sc between the aqueous phase and a cation exchanger at selenate concentrations in the range 0 to 0.167 M. Sodium perchlorate was added to keep the ionic strength at / = 0.5 M. The radioactive nuclide Sc was used to follow the distribution ratio at a total scandium concentration of 2 x 10 M. Measurements were carried out at 298.15, 308.15, and 318.15 K and the pH was adjusted to 4.0 to 4.5. No disturbance from the hydrolysis of Sc occurs at this pH according to the paper although this would be expected from the data in [76BAE/MES]. 

Anisole can be acylated with acetic anhydride in 99% yield (6.12). Yttterbium triflate can also be used. The yields are low when there is no activating group in the ring. The rate is accelerated by the addition of lithium perchlorate.56 Acylation of alcohols works well with 1 mole% of scandium triflate as a catalyst (6.13).57 The less toxic toluene has also been used as the solvent in such acylations. The... 

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