Nitrile and Cyanohydrin Hydration with Nanoparticles Formed In Situ from a Platinum Dihydride Complex

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

“…The poor reactivity observed was ascribed to the low stability of the cyanohydrin substrates, which slowly equilibrate in solution with HCN and the corresponding aldehyde or ketone (Scheme 23), and the irreversible coordination of the cyanide anion to platinum leads to the deactivation of the catalyst. In fact, most of the nitrile hydration catalysts reported to date are poisoned by cyanide and, therefore, with some notable exceptions [84][85][86][87][88][89], are inoperative with this particular class of nitriles. Although with only one example, Parkins and co-workers showed that this limitation can be circumvented, protecting the OH group of the cyanohydrin prior to the hydration reaction [90].…”

Access to α‐ and β‐Hydroxyamides and Ureas Through Metal‐Catalyzed C≡N Bond Hydration and Transfer Hydration Reactions

“…In a subsequent study, Tyler and co-workers reported the quantitative hydration of glycolonitrile and lactonitrile at r.t. employing Pt NPs, which showed to be relatively resistant to inhibition by cyanide. [26] In fact, experiments carried out in the presence of KCN showed that complete poison of the NPs only occurs when a large excess of KCN is added to the medium, a result that contrasts with the typical behavior of homogeneous catalysts, where 3 equivalents of cyanide are enough to render the catalyst completely inactive. [14,27] Also of note is the fact that, when acetone cyanohydrin was employed as substrate, 2hydroxyisobutyramide was formed in a remarkable 30 % yield before the cyanohydrin decomposed entirely.…”

“…[14,27] Also of note is the fact that, when acetone cyanohydrin was employed as substrate, 2hydroxyisobutyramide was formed in a remarkable 30 % yield before the cyanohydrin decomposed entirely. [26] Finally, a very recent work by Naka and co-workers deserves to be particularly highlighted since they were able to develop a protocol for the conversion of both aldehyde and ketone cyanohydrins into α-hydroxyamides applying a transfer hydration strategy. [28] As shown in Scheme 13, the process was conducted in acetic acid at 50°C, employing Pd(NO 3 ) 2 as the catalyst and a primary amide (hexanamide, octanamide, or acetamide) as the water donor.…”

Hydration of Cyanohydrins by Highly Active Cationic Pt Catalysts: Mechanism and Scope

“…15 well as Pt and Ag nanoparticles. 20,21 Although only aldehydederived cyanohydrins [glycolonitrile (1), lactonitrile (2), and 2-hydroxybutyronitrile (4)] were hydrated with complete conversion, these valuable studies present a benchmark for future investigation on cyanohydrin hydration using metallic catalysts. Bera et al developed a base-free Ni II -catalyzed protocol for hydration of mandelonitrile and its derivatives.…”

“…Therefore, despite the general utility of previously developed catalytic protocols for nitrile hydration, ,,− hydration of cyanohydrins still remains a long pursued but unsolved challenge in both industrial and academic settings. For instance, methacrylate monomers that represent a large global market for commercial products are primarily generated from hydration of acetone cyanohydrins and dehydration with concentrated sulfuric acid, but the production of considerable amounts of ammonium hydrogen sulfate is a major environmental drawback that requires additional disposing steps. , Only six cyanohydrins and their derivatives have been reported to be hydrated directly by water in the literature [Figure B­(1)]. − Pioneering work by Parkins et al revealed one of the most reactive and versatile catalysts [PtX­{(PR 2 O) 2 H}­(PR 2 OH), X = Cl or H] for nitrile hydration. − However, the efficiency for cyanohydrin hydration by Parkins’ catalysts was much lower than that observed with nitriles, and only lactonitrile ( 2 ) and 2-hydroxybutyronitrile ( 4 ) can be hydrated . Tyler et al systematically studied hydration of cyanohydrins.…”