619-25-0Relevant articles and documents
Transition State Differences in Hydrolysis Reactions of Alkyl versus Aryl Phosphate Monoester Monoanions
Grzyska, Piotr K.,Czyryca, Przemyslaw G.,Purcell, Jamie,Hengge, Alvan C.
, p. 13106 - 13111 (2003)
Although aryl phosphates have been the subject of numerous experimental studies, far less data bearing on the mechanism and transition states for alkyl phosphate reactions have been presented. Except for esters with very good leaving groups such as 2,4-dinitrophenol, the monoanion of phosphate esters is more reactive than the dianion. Several mechanisms have been proposed for the hydrolysis of the monoanion species. 18O kinetic isotope effects in the nonbridging oxygen atoms and in the P-O(R) ester bond, and solvent deuterium isotope effects, have been measured for the hydrolysis of m-nitrobenzyl phosphate. The results rule out a proposed mechanism in which the phosphoryl group deprotonates water and then undergoes attack by hydroxide. The results are most consistent with a preequilibrium proton transfer from the phosphoryl group to the ester oxygen atom, followed by rate-limiting P-O bond fission, as originally proposed by Kirby and co-workers in 1967. The transition state for m-nitrobenzyl phosphate (leaving group pKa 14.9) exhibits much less P-O bond fission than the reaction of the more labile p-nitrophenyl phosphate (leaving group pKa = 7.14). This seemingly anti-Hammond behavior results from weakening of the P-O(R) ester bond resulting from protonation, an effect which calculations have shown is much more pronounced for aryl phosphates than for alkyl ones.
Reactivity of secondary N-alkyl acrylamides in Morita–Baylis–Hillman reactions
Ahmar, Mohammed,Queneau, Yves,Verrier, Charlie,Yue, Xiaoyang
, p. 319 - 330 (2021/10/29)
The Morita–Baylis–Hillman (MBH) reaction of secondary N-alkyl acrylamides, discarded up to now from investigations of the scope of activated alkenes, was studied. Optimization of the reaction conditions revealed that a balance must be found between activation of the MBH coupling reaction and that of the undesired competitive aldehyde Cannizzaro reaction. Using 3-Hydroxyquinuclidine (3-HQD) in a 1:1 water-2-MeTHF mixture provides the appropriate conditions that were applicable to a wide range of diversely substituted secondary N-alkyl acrylamides and aromatic aldehydes, giving rise to novel amide-containing MBH adducts under mild and clean conditions.
Efficient Solvent-Free Hydrosilylation of Aldehydes and Ketones Catalyzed by Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH
Fang, Fei,Chang, Jiarui,Zhang, Jie,Chen, Xuenian
, p. 3509 - 3515 (2021/03/16)
An efficient solvent-free catalyst system for hydrosilylation of aldehydes and ketones was developed based on iron pre-catalyst Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH. The reactions were tolerant of many functional groups and the corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the reaction products. The reaction is likely catalyzed by an in situ generated pincer ligated iron hydride complex. Graphic Abstract: [Figure not available: see fulltext.]
Scope and limitations of biocatalytic carbonyl reduction with white-rot fungi
Zhuk, Tatyana S.,Skorobohatko, Oleksandra S.,Albuquerque, Wendell,Zorn, Holger
supporting information, (2021/02/02)
The reductive activity of various basidiomycetous fungi towards carbonyl compounds was screened on an analytical level. Some strains displayed high reductive activities toward aromatic carbonyls and aliphatic ketones. Utilizing growing whole-cell cultures of Dichomitus albidofuscus, the reactions were up-scaled to a preparative level in an aqueous system. The reactions showed excellent selectivities and gave the respective alcohols in high yields. Carboxylic acids were also reduced to aldehydes and alcohols under the same conditions. In particular, benzoic, vanillic, ferulic, and p-coumaric acid were reduced to benzyl alcohol, vanillin, dihydroconiferyl alcohol and 1-hydroxy-3-(4-hydroxyphenyl)propan, respectively.