Enantioselective Nickel-Catalysed Domino and Tandem Reactions
The fourth chapter of the book illustrates how much asymmetric nickel catalysis has contributed to the development of novel enantioselective domino, multicomponent, and tandem sequential reactions. It updates the major progress in the field of enantioselective two- and multicomponent domino reactions as well as tandem sequences promoted by chiral nickel catalysts, covering the literature since the beginning of 2004. It well illustrates the power of these fascinating one-pot processes, following the same principles that are found in biosynthesis from the nature. During the last 10 years, an impressive number of novel powerful asymmetric domino and multicomponent processes have been developed on the basis of asymmetric nickel catalysis. In particular, a number of enantioselective Michael-initiated domino reactions have been described, involving nitroalkenes as well as various α,β-unsaturated carbonyl compounds as acceptor-activated alkenes, which provided a wide variety of chiral functionalised (poly)cyclic products in enantioselectivities uniformly excellent. Moreover, other types of enantioselective novel two-component domino reactions have been successfully catalysed by chiral nickel complexes. In the context of enantioselective nickel-catalysed multicomponent reactions, many excellent results have also been achieved, as well as in the area of enantioselective tandem sequences. The economic interest in combinations of asymmetric nickel catalytic processes with the concept of domino, multicomponent, and sequential reactions is obvious, and has allowed reaching easily high molecular complexity with often excellent levels of stereocontrol with simple operational one-pot procedures, and advantages of savings in solvent, time, energy, and costs by avoiding costly protecting groups and time-consuming purification procedures after each step.