ABSTRACT
The special utility of dihalide-derived di-Grignard reagents in the synthesis of cyclic metallocycles and carbo cycles has required that a special section be devoted to the preparation and reaction of these species [ 1 ,2]. Reactions of magnesium, especially Rieke magnesium, with dienes to form magnesiacycloalkanes and spiroannelation reactions of di-Grignard reagents are covered specifically in Chapters 26 and 27, respectively. The ability to form di-Grignard reagents is largely a function of the positional relationship of l ,x (x = 1 , 2, . . · n)-dihalide substituents on alkyl, alkenyl, alkynyl, aryl, and benzyl or allyl substrates; therefore, the discussion will be based on dihalide substrates. Di-Grignard reagent formation can be strongly dependent on choice of halogen, solvent, concentration, and type of activated magnesium.
