I. Advances in heterogeneous nickel-catalyzed reactions. II. Copper(I) chloride as a quick and efficient phosphine scavenger. III. Advances in copper hydride chemistry.

摘要

Group 10 metals, such as palladium and nickel, have a rich history in cross-coupling reactions for the formation of C-C, C-N, and C-H bonds. Due in part to economics, nickel catalysts have received much attention as an alternative to more expensive palladium catalysts. With environmental concerns in mind as well, nickel-in-charcoal and nickel-on-graphite were developed as heterogeneous catalysts for cross-coupling and other organic transformations. These catalysts can be recycled without loss of activity. In addition, microwave irradiation was employed as a means of significantly increasing the rates in several of those nickel-catalyzed reactions.; Quick and efficient purification of organometallic reactions that rely on phosphine ligands is a significant problem for industrial processes. Not only is the removal of such ligands sometimes difficult, but often the recovery of nonracemic phosphine ligands is an important feature. With this in mind, copper(I) chloride was found to be a fast and efficient scavenger of phosphines from a variety of organometallic transformations. Re-isolation of nontrivial phosphines was possible using a dithiocatechol dilithium salt, which irreversibly binds to copper, thus releasing phosphines for easy re-isolation.; Asymmetric hydrosilylation employing several metal-based catalysts (i.e., Rh, Ru, Ti, and Cu) have received much attention by the scientific community over the past quarter century. Success has been attributed in large measure to the creative design of novel nonracemic ligands which increase the stability and efficiency of these catalysts. Copper hydride (CuH) catalyzed asymmetric hydrosilylations is an especially mild and efficient method for the reduction of prochiral ketones, imines, and alpha,beta-unsaturated carbonyl derivatives. With this in mind, the first "copper hydride in a bottle" was developed for quick and efficient asymmetric hydrosilylations. The innate stability of these nonracemically-ligated copper hydrides set the stage for the first microwave assisted reactions of copper hydride at elevated temperatures with little to no loss in enantioselectivity. In addition, a new heterogeneous copper catalyst, copper-in-charcoal (Cu/C), was developed and employed in asymmetric hydrosilylations offering opportunities for reuse with no loss in activity.