Benz-amidinato calcium iodide catalyzed aldehyde and ketone hydroboration with unprecedented functional group tolerance

Abstract

A benz-amidinato calcium compound, [PhC(NiPr)CaI] (1), catalyzed hydroboration of a wide range of aldehydes and ketones using pinacolborane (HBpin) at room temperature is reported. The catalyst shows functional group tolerance even towards OH and NH groups. The strategy was further extended to imines.

Calcium Amido Complexes Coordinated by Tridentate Amidinate Ligands: Synthesis, Structures and Catalytic Activity in Olefin Hydrophosphination and Polymerization of Cyclic Esters

“…Two past decades are marked by significant advances in the synthesis of organic derivatives of alkaline earth elements and investigation of their structures and reactivity which resulted in the discovery of formerly unexpected rich catalytic potential of these compounds The increasing interest in the application of alkaline earth metal complexes in homogeneous catalysis is inspired by their non‐toxicity, low cost and prevalence of these elements in the earth′s crust . Thus, calcium amido complexes have been used as catalysts (or precatalysts) for ring‐opening polymerization (ROP) of cyclic ethers,, Tishchenko′s reaction, hydroamination‐cyclization, hydroamination,, hydrosilylation, hydroboration,, hydrophosphination, hydrophosphorylation of aldehydes and ketones, hydrogenation of activated alkenes, reactions of dehydrocoupling of amines with silanes,, dehydrocoupling of aminoboranes …”

Catalyst‐Free and Solvent‐Free Facile Hydroboration of Imines

“…Among metal catalyzed processes, transition metal and even rare earth metal complexes have been studied (Scheme ). There is also a recent surge in utilization of s ‐ and p ‐block elements and till date, several research groups have studied the hydroboration of carbonyl and to some extent imine compounds using main‐group element (Ca, Mg, Al,– Si) based systems (Scheme ). Alkali metal based compounds for example, n BuLi and NaOH have also been utilized for the same process .…”

A greener catalyst for hydroboration of imines—external electric field modify the reaction mechanism

“…What is more, imines are readily available from the condensation of carbonyl compounds and primary amines and are, thus, the precursors of choice for the synthesis of unsymmetrically substituted secondary amines . Although the hydroboration of imines had been reported more and more, it is worth noting that hydroboration of C═N bonds with organoboranes or borohydrides is a workhorse reaction for the mild reduction of imines into amines. Especially, the use of deactivated hydroboranes, such as catecholborane (HBCat, Cat = catechol) and pinacolboane (HBPin, Pin = pinacol), requires catalysis due to the significantly decreased Lewis acidity of the boron center.…”