Ru-, Rh-, and Pd-Catalyzed C-C Bond Formation Involving C-H Activation and Addition on Unsaturated Substrates: Reactions and Mechanistic Aspects Vincent Ritleng, Claude Sirlin, and Michel Pfeffer* Laboratoire de Synthe `ses Me ´tallo-Induites, UMR CNRS 7513 Universite ´ Louis Pasteur, 4, rue Blaise Pascal 67070 Strasbourg, France Received October 13, 2001 Contents I. Introduction 1731 II. Functionalization of Aromatic or Acetylenic C-H Bonds by Coupling Reactions with Multiple C-C Bonds 1731 A. Arylation of C-C Double Bonds 1731 1. Chelation-Assisted Reactions 1732 2. Nonchelation-Assisted Reactions 1733 B. Hydroarylation of C-C Double Bonds 1737 1. Chelation-Assisted Reactions 1737 2. Nonchelation-Assisted Reactions 1743 C. Hydroarylation of C-C Triple Bonds 1743 1. Chelation-Assisted Reactions 1743 2. Nonchelation-Assisted Reactions 1744 D. Homo- and Heterocoupling of Terminal Alkynes 1747 1. Terminal Alkyne Dimerization and Cross-Coupling with Internal Alkynes 1747 2. Cross-Coupling of Terminal Alkynes with Alkenes 1751 III. Functionalization of Aromatic or Aliphatic C-H Bonds by Coupling Reactions with Carbon Monoxide 1753 A. Carbonylation of Arenes and Alkanes 1753 B. Intermolecular Hydroacylation 1756 1. Chelation-Assisted Reactions 1756 2. Nonchelation-Assisted Reactions 1758 C. Intramolecular Hydroacylation 1759 D. Aryl Acylation by Carbon Monoxide and Olefins 1763 1. Chelation-Assisted Reactions 1763 2. Nonchelation-Assisted Reactions 1765 IV. Conclusion 1766 V. References 1766 I. Introduction For a long time synthetic chemists have been interested in the elaboration of the cheapest and cleanest routes for the synthesis of organic molecules. However, over the last few decades the quest for the most economic ways to the formation of C-C bonds has become a matter of increasing importance among both industrial and academic research units. Thus, for instance, the concept of atom economy 1 has frequently been used to emphasize the minimal number of reactants. Another way to achieve clean and economically interesting processes is the selec- tion of “low-energy” starting materials as substrates. Among these, substrates which contain a reactive C-H bond rather than a C-X bond would provide very interesting alternatives for synthetic purposes, 2 provided that these reactions are achievable under acceptable thermodynamic conditions such as mild temperatures and low pressures. The aim of this review is indeed to document the various reactions known for forming C-C bonds starting with the least activated substrates. We have, thus, chosen to select those reactions which lead to the formation of one C-C bond starting from an unactivated C-H bond. In addition, to fulfill the atom economy requirement, we have only selected the reactions for which the C-H unit is added onto unsaturated substrates such as olefins, alkynes, and carbonyls. However, one important exception to this rule was the occurrence of some interesting Heck- type reactions 3 whereby the hydrogen atom is for- mally lost in the last -elimination step of the process (see section II.A). We only report procedures catalyzed by the Ru, Rh, Pd triad. Indeed, these metals are by far the most used from the periodic table in catalysis, 4 and thus, they allow a somewhat complete coverage of the various possibilities offered in this area of research. Recent reviews 4b,c have appeared on a topic related to the one of this paper. However, as well as other differences, these works did not analyze the coupling processes from a mechanistic point of view. In op- position, we have chosen to focus on the mechanistic aspect of the various reactions studied as it is well- known that an understanding of the mechanism of a given reaction can lead to better opportunities for improving the successful reactions and open up the possibility of discovering novel reactions. II. Functionalization of Aromatic or Acetylenic C-H Bonds by Coupling Reactions with Multiple C-C Bonds A. Arylation of C-C Double Bonds Derivatives from aromatic compounds such as alkylbenzenes, phenol, aniline, and naphthalene are large-quantity chemicals manufactured by the chemi- cal industry. Styrene is the most prevalent member of the benzene family. Since the current industrial * To whom correspondence should be addressed. Phone: +33 3 90241522. Fax: +33 3 90241526. E-mail: pfeffer@ chimie.u-strasbg.fr. 1731 Chem. Rev. 2002, 102, 1731-1769 10.1021/cr0104330 CCC: $39.75 © 2002 American Chemical Society Published on Web 04/04/2002