Lewis acids copper bromide

Many of the d-block elements form characteristically colored solutions in water. For example, although solid copper(II) chloride is brown and copper(II) bromide is black, their aqueous solutions are both light blue. The blue color is due to the hydrated copper(II) ions, [Cu(H20)fJ2+, that form when the solids dissolve. As the formula suggests, these hydrated ions have a specific composition they also have definite shapes and properties. They can be regarded as the outcome of a reaction in which the water molecules act as Lewis bases (electron pair donors, Section 10.2) and the Cu2+ ion acts as a Lewis acid (an electron pair acceptor). This type of Lewis acid-base reaction is characteristic of many cations of d-block elements. 

In the improved synthesis of Ifetroban described above, environmental concerns due to special handling of copper bromide waste and hazards associated with hexa-methylene tetramine (HMT) on manufacturing scale led to further perfection of the synthesis. Mechanistic considerations suggested that an oxidized form of aminoamide B (Scheme 4) would eliminate the necessity for a late-stage copper-mediated oxidation. This was indeed accomplished. The cyclization-elimination sequence was initiated by a Lewis acid and completed by base-mediated elimination to afford the Ifetroban penultimate. In addition to eliminating the need for copper bromide and HMT, this modification helped to reduce the cost of the product by an additional 15%. 

A diazonium salt reacts with copper(I) chloride or copper(I) bromide to form an aryl chloride or aryl bromide, respectively. This is called the Sandmeyer reaction. It provides an alternative to direct chlorination and bromination of an aromatic ring using CI2 or Br2 and a Lewis acid catalyst. 

A.3 Lewis Acid/Metal Salt Superacids. - Superacid active catalysts may be obtained by the grinding of aluminium bromide or chloride with some salts. The reaction of AlBr with titanium, copper, iron, aluminium, nickel sulphates, aluminium or titanium chlorides results in catalytic systems able to initiate n-pentane isomerization even at room temperature.The soluble complex of AlBr-j with salts is a true catalyst. Aluminium trichloride... 

A mild Lewis-acid-catalysed enantioselective Henry reaction has been carried out in water at 0 °C, using copper(II) bromide and a prolinol with a pendant phenol (69) yields and ee up to 99% were obtained. ... 

Addition to vinyl ethers and vinyl esters is regioselective, leading to the corresponding j8-alkyloxy/acyloxy sulfone. Addition to alkynes gives vinyl sulfones via a radical pathway. These reactions can be carried out in the presence of peroxide initiators, with Lewis acids such as copper(II) bromide (eq 4), or thermally (eq 5). - ... 

The position of copper(I) salts as quite soft Lewis acids has resulted in a significant number of publications where soft phosphorus- and sulfur-containing ligands have been used and shown to enhance the catalytic process in CuAAC reactions. A variety of phosphorus-containing ligands has been used to produce significant rate enhancements or improved efficiency in CuAAC reactions. Examples include the use of triphenylphosphine-copper(I) bromide [137] (e.g., in the synthesis of dendrimers [138]), phosphoramidites [139], and bis(triphenylphosphine)-copper(I) carboxylates [140]. In addition, triethylphosphite-copper(I) iodide complexes have been used in sugar chemistry [141]. 

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