Efficient Hydroboration of Esters and Nitriles Using a Quinazolinone‐Supported Titanium(IV) Multitasking Catalyst

Abstract

We report catalytic hydroboration of esters as well as nitriles under solvent‐free and mild conditions using single titanium(IV) metal complex, [{κ2‐C6H4C(O)N(iPr)C(N‐iPr)=N}{κ3‐(iPr)N=C(O)−C6H4−NC(NMe2)N(iPr)}TiNMe2] 1 as a sustainable, economical, and efficient pre‐catalyst. The molecular structure of the TiIV complex in the solid state reveals the unique coordination of TiIV metal with N, N, and O atoms of one quinazolinone unit via in‐situ rearrangement, while another quinazolinone moiety coordinates in bidentate fashion via both N atoms only. The TiIV complex demonstrates excellent activity as a pre‐catalyst towards the hydroboration of a wide array of esters and nitriles with pinacolborane (HBpin) to afford alkoxyboranes and diboryl amines in high yield (up to 99 %) with greater tolerance to a variety of electron‐withdrawing and electron‐donating functional groups. A most plausible mechanism of hydroboration of esters is also proposed based on kinetics and NMR studies, which suggests the formation of titanium‐hydride species as an active catalyst.