Copper(II) trifluoromethanesulfonate

Abstract

A) He et al. reported a mild and efficient copper(II) triflate-catalyzed procedure for the Nazarov cyclization of polarized divinyl ketones. (Diagram presented). B) Our group reported unexpected ring expansion from activated quinoline and isoquinoline by using diazocarbonyl compounds via C-C insertion in the presence of 5 mol% of copper triflate to produce ethyl 1H-benzo[b]azepine- 1-carboxylate and ethyl 3H-benzo[d]azepine-3-carboxylate, respectively, in excellent yields and with a high degree of selectivity. The products represent an important moiety in many pharmaceutically active naturally occurring molecules. (Diagram presented). C) The combination of a bis(isopropyloxazole) and Cu(OTf)2 proved to be an efficient catalyst in the asymmetric Friedel-Crafts reaction of indoles with arylidene malonates. In isobutanol, the S-enantiomer was obtained in up to 97% ee, while the opposite enantiomer was obtained in up to 78% ee in CH2Cl2 or 1,1,2,2- tetrachloroethane. (Diagram presented). D) Asao and co-workers reported the [4+2] cycloaddition reaction between o-alkynyl(oxo)benzene and olefins in the presence of catalytic amount of Cu(OTf)2. The reaction affords 1,2-dihydronaphthalene derivatives bearing an oxo function at the 1-position. The reaction proceeds most probably through the formation of benzo[c]pyrylium cupric ate complex. (Diagram presented). E) Kobayashi et al. developed catalytic asymmetric Mannich-type reactions of N-acyl esters with silylenol ethers or alkyl vinyl ethers using Cu(OTf)2-chiral diamine complexes as the catalyst. The reaction proceeded smoothly at 0 °C in most cases, and high yields and high diastereoselectivies were attained. This method is useful for the preparation of N-acetylated amino acid derivatives, which are often observed in biologically important compounds such as peptides and ceramide. (Diagram presented). F) Degrade et al. reported an efficient and highly selective Cu-catalyzed asymmetric conjugate addition of alkylzincs to trisubstituted cyclic enones. This transformation is catalyzed by Schiff base derivatives of a single amino acid that is commercially available and inexpensive (L- or D-valine). The ligand can be prepared and used directly, without isolation or purification, to afford products with high enantioselectivities. (Diagram presented). G) Lu et al. reported the smooth addition of phenylacetylene to aromatic ketones in the presence of catalytic amounts of Cu(OTf)2 and camphorsulphonamide. The corresponding tertiary propargylic alcohols were obtained in high yields and with up to 97% ee. This reaction represents a highly enantioselective catalytic addition of dialkynyl zinc reagents to simple ketones. (Diagram presented).