Heteroatomic coupling reaction numbers

Details on oxidation and reduction reactions mediated by [(NHC)Pd] complexes can be found in Chapters 12 and 13, respectively. Further reports of interest disclosed include diboration of alkenes catalysed by a pincer complex, deuteration of C-H bonds with an N,0-functionalised NHC complex, and an intriguing Suzuki-type reaction of [FeI(Cp)(CO)2] with arylboronic acids. A number of useful C-heteroatom coupling reactions have also been reported recently, including alkene hydrophosphination and alkyne silylation. ... 

The biaryl synthesis by Ullmann coupling, as well as a large number of related coupling reactions, constitutes another type of copper-mediated or -catalyzed reaction used extensively for the formation of carbon-carbon and carbon-heteroatom bonds. These transformations have been reviewed recently17,177,177a,177b and will not be discussed in detail here. 

A number of aryl halides and aryhnetals, especially those containing heteroatoms, are formally represented as a,/3-unsaturated carbonyl derivatives. Although their cross-coupling reactions may be formally classified as conjugate substitution processes, various requirements for these cases may be significantly different than in those cases discussed in Sects. B and C because of their aromatic nature. For this reason, specific examples of these reactions together with those of the reactions of quinone derivatives are discussed separately in Sect. D. 

Click chemistry comprises a number of organic heteroatom coupling procedures that comply with the stringent criteria as defined by Sharpless (see also Chapter 2) (Kolb et al, 2001). Among these click reactions, the copper-catalyzed azide-alkyne cycloaddition reaction... 

Formally copper catalyzed couplings are analogous to palladium and nickel catalyzed reactions. Carbon-carbon and carbon-heteroatom bonds can be formed in such transformations alike. From the mechanistic point of view there is a significant difference between nickel, palladium and copper catalyzed processes however. While in the former cases the catalyst usually oscillates between the 0 and +2 oxidation states, in copper mediated transformations the common oxidation numbers are +1, +2 and +3. 

A very large number of these systems with ring junction heteroatoms exists, and this number is constantly increasing. Only illustrative examples of the preparation of such systems can be given here. The synthetic methods for the formation of this type of heterocycle can be usefully classified as follows (i) various cyclocondensations between the corresponding heterocyclic derivatives and bifunctional units, (ii) intramolecular cyclizations of electrophilic, nucleophilic or (still rare) radical type, (iii) cycloadditions, (iv) intramolecular oxidative coupling, (v) intramolecular insertions, (vi) cyclization of open-chained predecessors, (vii) various reactions (quite often unusual) which are specific for each type of system. Examples given below illustrate all these cases. 

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