A comprehensive study of the effects of spectator ligands, transition metals and lithium halide additives on the efficiency of iron, nickel and palladium-catalyzed cross-coupling reactions of cyclohexyl magnesium bromide with fluorinated bromobenzenes

Abstract

Thirteen mono-, bis-and trifluorinated bromobenzene derivatives have been coupled with cyclohexyl magnesium bromide or the corresponding lithiumchloride or lithiumbromide adducts. Iron, nickel and palladium complexes of the general formula [MCl2(dppx)] (x = (CH2)n, n = 1, 2, 3) have been used as the precatalysts. Palladium based catalysts give high yields of the coupling product with the Grignard reagent itself whereas lithium halides are needed as additives to achieve comparable efficiencies if nickel and iron catalysts are used. Yields also depend on the chain length of the bridging units and on the fact whether fluorine substituents are present in ortho position with respect to bromine.

Cobalt, copper, and chromium-catalyzed carbon-carbon coupling reactions using a broad spectrum of Grignard reagents as reaction partners

“…27 During the past century, Grignard reagents have been the most widely used organometallic reagents. [31][32][33][34][35][36] They remain desirable coupling partners owing to their stability and ease of preparation, with many representatives being commercially available. 37,38 Chromium is among the most abundant elements on earth.…”

Nickel and palladium catalyzed Kumada-Tamao-Corriu cross-coupling reactions: scope and recent advances

“…35 Phosphine ligands with high electron density increase the reactivity of metal center towards oxidative addition, and their bulkiness facilitates the formation of the coordinatively unsaturated species as well as the reductive elimination. 36,37…”