Readily available lithium compounds as catalysts for the hydroboration of carbodiimides and esters

Abstract

Selective and efficient hydroboration of esters and carbodiimides to alcohols and amines by two well-defined and readily accessible lithium complexes, 2,6-di-tert-butyl phenolate lithium (1a) and 1,1’-dilithioferrocene (1b) are described. A range of aliphatic, aromatic, and cyclic esters with various functional groups were selectively converted into the corresponding boronate esters. Similarly, the single hydroboration of carbodiimides with aliphatic and aromatic substituents on the nitrogen atoms was studied. A possible mechanistic pathway of the hydroboration of carbodiimides with HBpin has been proposed using NMR studies and DFT calculations. These reactions are convenient alternatives to stoichiometric hydride reduction or hydrogenation. The employing of lithium complexes is also significant, because of the need to find cheap and green alternatives to noble metal complexes.