Rhenium-catalysed hydroboration of aldehydes and aldimines.

The first examples for the rhenium-catalysed hydroboration of aldehydes, ketones and aldimines, including heteroaromatic quinoline, are reported herein. Reactions are remarkably chemoselective and tolerant of several functional groups. A wide array of rhenium complexes were efficient pre-catalysts for these hydroborations, including new low-valent complexes of the formula [Re(N-N)(CO)(L)]X (N-N = bipy derivative, L = labile ligand/solvent, and X = [BAr] and [B(3,5-di-tBu-cat)]), which have been characterized fully including an X-ray diffraction study for [Re(bipy)(CO)(quin)][BAr] (2). A new silver spiroboronate ester Ag[B(3,5-di-tBu-cat)](NCCH) (3) was prepared and characterized fully, including an X-ray diffraction study, and used to make one of the new rhenium complexes.