Asymmetric catalysis by bifunctional BINOL-based catalysts

Several new bifunctional BINOL-based ligands are synthesized by one step Mannich type reactions. In comparison with the same type of ligands reported before, this simplified synthesis has made ligands 3,3'-bismorpholinylmethyl BINOL and 3,3'-bismorpholinylmethyl H8BINOL much more readily accessible. The 3,3'-bismorpholinylmethyl H8BINOL is found to be highly enantioselective for the reaction of diphenylzinc with both aliphatic and aromatic aldehydes and in particular to be the most enantioselective catalyst for linear aliphatic aldehydes. The mild reaction conditions make this chiral catalyst practically useful for organic synthesis. The mechanism of this reaction has been studied. This H8BINOL derivative can also catalyze the enantioselective reaction of alkynes with aldehydes. 3,3'-bismorpholinylmethyl BINOL in combination with Me2AlCl is a highly enantioselective catalyst for the addition of TMSCN to various aldehydes, especially aliphatic aldehydes with diverse structures. This catalyst system is among the most practical ones. A remarkable positive nonlinear effect is found for this chiral ligand.