The catalytic hydration of nitriles to amides using a homogeneous platinum phosphinito catalyst

Synthetic Applications of the Parkins Nitrile Hydration Catalyst [PtH{(PMe2O)2H}(PMe2OH)]: A Review

“…The reaction proceeds at room temperature, and the complex precipitates directly in the medium, thus making its isolation easy by simple filtration (isolated yields are usually in the range 75%-80%) [16][17][18][19]. In their first studies, Parkins and Ghaffar demonstrated the ability of 1 to selectively hydrate different model nitrile substrates, such as benzonitrile, acetonitrile, acrylonitrile, or 3-cyanopyridine, employing water, aqueous ethanol, or aqueous THF as the reaction medium at 70-90 °C [16][17][18]. The remarkable activity of [PtH{(PMe2O)2H}(PMe2OH)] (1) was readily evidenced in these seminal works, with reported turnover frequencies exceeding 1400 h −1 and turnover numbers of up to 77,000.…”

“…Further evidence of the synthetic potential of complex [PtH{(PMe2O)2H}(PMe2OH)] (1) was given by de Vries and co-workers, who reported excellent yields and chemoselectivities in the hydration of a variety of sterically hindered tertiary nitriles and nitriles containing acid-or base-sensitive functional groups (some representative examples are shown in Figure 2) [21]. Concerning its mechanism of action, Ghaffar and Parkins proposed that in aqueous medium, protonation of the hydride ligand of 1 by water readily takes place, generating a vacant coordination site on the metal for substrate binding, with concomitant dihydrogen extrusion (Scheme 2) [16][17][18]. [22], and its congeners are considered to be important lead molecules for the development of new drugs for Mycobacterium tuberculosis infections [23].…”

Bifunctional Organometallic Catalysts Involving Proton Transfer or Hydrogen Bonding

“…[45,46] These complexes (schematically illustrated by 4; Scheme 4) appear to transfer hydrogen by a new, outer-sphere mechanism featuring cooperativity of metal and the NÀH moiety of an amine ligand. Other notable examples are 1) the Shvo catalyst recently studied by Caseys group; [47,48] 2) Sigmans alcohol oxidation catalyst, for which he proposes alcohol binding involving proton transfer; [49] 3) nitrile hydration by [Pt(L) n (R 2 PÀOH)] complexes (6; Scheme 4), [50][51][52] which are proposed to act by attack of the pendant hydroxyl on coordinated and activated nitrile functionality (forming 7 as an intermediate); and 4) nitrile hydration by [RuÀH(L) n ] complexes, in which the hydride ligand may activate attacking water through hydrogen bonding. [53] One particularly exciting precedent for some of our research is shown schematically by the proposed conversion of 8 to 9 (Scheme 4).…”

Efficient Hydration of Nitriles to Amides in Water, Catalyzed by Ruthenium Hydroxide Supported on Alumina

“…Many efficient methods that use microorganisms for enzymatic hydration of nitriles [5,6] or homogeneous complexes of transition metals such as cobalt, [7] copper, [8] molybdenum, [9] ruthenium, [10] rhodium, [11] palladium, [12,13] and platinum [14,15] have been reported. However, these systems have disadvantages: difficulty in catalyst/product separation and necessity of special handling of microorganisms and metal complexes.…”