Copper in cross-coupling reactions - The post-Ullmann chemistry

In the last decade, a number of methods using various copper complexes and salts to carry out cross-coupling reactions leading to the formation of C-heteroatom (C-N, C-O, C-S, C-P, C-Se), C-C, and C-metal bonds have been proposed. These methods aim at overcoming the deficiencies of conventional copper-assisted substitution methods (Ullmann chemistry) due to dramatic softening of reaction conditions, extension of scope towards unactivated substrates and new types of nucleophiles, and increasing tolerance to sensitive functionality. On the other hand, the scope and selectivity of copper-assisted methods are often complimentary to the parallel palladium-catalyzed cross-coupling methods. Both the new features and drawbacks of the new family of synthetic protocols are discussed. (C) 2004 Elsevier B.V. All rights reserved.