ABSTRACT
The most frequently used metal-catalyzed Grignard reactions' were those performed under ( 1 ) copper, (2) nickel, (3) palladium, or (4) titanium catalysis. Other types of metals, such as Ag, Fe, Co, Mn, Zr, and such, have sometimes been used to effect characteristic reactions, which will be collected together in the last Section VI. Each of the Sections II-VI will deal with both carbon-carbon bond formation and functional group transformation. The metal-catalyzed Grignard reactions are such standard methods in organic synthesis that they have been reviewed in many articles, as well as books and monographs, which have been updated from time to time based on the actively studied area at the moment. Thus, this small chapter includes a brief overview of the area of research, lists of review articles, typical or important types of reactions, and examples of the most recently reported reactions. The advantage of metal-catalyzed reactions such as ( 1 ) the success of a synthetic transformation that cannot be attained by Grignard reagent itself and (2) alternation of the reaction course (i.e., different chemo-, regio-and stereoselectivities attained in the presence of metallic additives) will be emphasized. [Abbreviations are defined in the Glossary following chapter text.]
Grignard reagents are generally reluctant to displace alkyl (except reactive alkyl groups such as allyl and benzyl) halides, sulfonates, or epoxides, owing to their low reactivities or the accompanying side reactions involving metal-halogen exchange and fJ-elimination. However, in the presence of a copper catalyst, Grignard reagents react cleanly with the foregoing electrophiles in good to excellent yields. This copper effect originated from Kharasch's report, in the early 1 940s, which mentioned that certain transition metals, such as CoCI2 , CrCI2 , or CuCI, facilitated the coupling of Grignard reagents with vinyl halides [Eq. ( 1 ); 4] .
