91012-00-9Relevant articles and documents
Hydration of Cyanohydrins by Highly Active Cationic Pt Catalysts: Mechanism and Scope
Li, Chengcheng,Chang, Xiao-Yong,Huo, Luqiong,Tan, Haibo,Xing, Xiangyou,Xu, Chen
, p. 8716 - 8726 (2021/07/26)
Cyanohydrins (α-hydroxy nitriles) are a special type of nitriles that readily decompose into hydrogen cyanide (HCN) and the corresponding carbonyl compounds. Hydration of cyanohydrins that are readily available through cyanation of aldehydes and ketones provides the most straightforward route to valuable α-hydroxyamides. However, due to low stability of cyanohydrins and deactivation of the catalysts by the released HCN, catalytic direct hydration of cyanohydrins still remains largely unsolved. As a general trend, cyanohydrins containing bulkier substituents, such as α,α-diaryl cyanohydrins, degrade more quickly and thus are more difficult to be hydrated. Here, we report development of cationic platinum catalysts that exhibit high reactivity for hydration of various cyanohydrins. Detailed mechanistic investigations for hydration of nitriles by (PμP)Pt(PR2OH)X(OTf) reveal a catalytic cycle involving the formation of a five-membered metallacyclic intermediate and subsequent hydrolysis via attacking on the phosphorus of the secondary phosphine oxide (PR2OH) ligand by H2O. We discovered that Pt catalyst A bearing the electron-rich, appropriately small-bite-angle bisphosphine ligand provides super reactivity for hydration of cyanohydrins. The hydration reactions catalyzed by A proceed at ambient temperatures and occur with a wide variety of cyanohydrins, including the most difficult α,α-diaryl cyanohydrins, with good turnover numbers.
A mild hydration of nitriles into amides
Breuilles,Leclerc,Uguen
, p. 1401 - 1404 (2007/10/02)
Stirring mixtures of β-hydroxynitriles with manganese dioxide, deposited onto silica gel for a few days at room temperature resulted in the formation of the corresponding amides in fair to good yields. The unprecedented conversion of 3-hydroxyglutarodinitrile into the corresponding monoamide has been performed by this methodology.
Optically Active Alcohols from 1,3-Dioxan-4-ones. A Practical Version of Enantioselective Synthesis with Nucleophilic Substitution at Acetal Centers
Seebach, Dieter,Imwinkelried, Rene,Stucky, Gerhard
, p. 448 - 464 (2007/10/02)
Secondary alcohols in enantiomeric excesses above 90percent are accessible from 2-substituted 6-methyl-1,3-dioxan-4-ones.The dioxanones are prepared from aldehydes and readily available (R)- or (S)-3-hydroxybutanoic acid.Treatment of the dioxanones with silyl nuclophiles or triisopropoxy(methyl)titanium in the presence of yields the corresponding 3-alkoxy acids in diastereoselectivities >/= 95percent.The 'chiral auxiliary" is removed from the alkoxy acids by treatment with LiN(i-Pr)2 to give the secondary alcohols with >/= 90percent ee. cis/trans-Mixtures (9:1) of the dioxanones furnish products of the same configurational purity as those obtained from pure cis-isomers.In comparison with other variants of enantioselective syntheses with nucleophilic substitution at acetal centers, the following advantages of the dioxanone method are noteworthy: i) (R)- and (S)-3-hydroxybutanoic acids are both readily available; ii) reactions are not sensitive to changes in conditions; iii) the 'chiral auxiliary' is removed simply by base elimination, no oxidation is required; iv) no chromatographic purification steps are necessary.The overall reaction described here is an enantioselective nucleophilic addition to aldehydes with concomitant dehydration of enantiomerically pure 3-hydroxybutanoic to crotonic acid.
