Planar-chiral heterocycles as ligands in metal-catalyzed processes: enantioselective addition of organozinc reagents to aldehydes

摘要

As part of a program directed toward the development of new families of chiral nucleophilic catalysts and new classes of chiral ligands, we have begun to explore the chemistry of 2-substituted heterocycles that are π-bound to transition metals (e.g., 1).~1 Such complexes are chiral by virtue of the presence of ML_n and the differentiation of R from H, and the asymmetric environment around the Lewis-basic heteroatom can readily be "tuned" by varying the steric bulk either of the metal fragment or of R.