Racemic esters of 1-phenyl- and 1-(pyridyl)ethyl acetates 1a–c (R = Me, Ph) were subjected to hydrolysis in water in the presence of Candida rugosa lipase (CRL). 1-Pyridylethyl acetates (1, R = Me) are hydrolyzed by crude CRL (C-CRL) and isopropanol (isopropyl alcohol) treated CRL (PT-CRL) at very low rates, and the enantiorecognition was disappointing. By using 1-pyridylethyl benzoates (1, R = Ph) the results differed greatly: hydrolysis occurred much faster, and the enantiorecognition was good for 3- and 4-pyridyl derivatives and excellent for 2-pyridyl derivative. Analogous results were obtained by submitting the 1-phenylethanol esters 4 to enzymatic hydrolysis under the same experimental conditions. The hydrolysis of methyl o-acetoxybenzoates 7 (R = Me) gave quantitatively the deacetylated methyl o-hydroxybenzoates 9 (R = Me) by using either C-CRL or PT-CRL. A complete reversed selectivity is observed in the hydrolysis of phenyl o-acetoxybenzoates 7 (R = Ph) catalyzed by PT-CRL. Molecular modeling studies, aimed at probing the substrate specificity and the enantioselectivity of enzyme in terms of its three-dimensional structure is reported.
Systematic Evaluation of Sulfoxides as Catalysts in Nucleophilic Substitutions of Alcohols
作者:Sebastian Motsch、Christian Schütz、Peter H. Huy
DOI:10.1002/ejoc.201800907
日期:2018.9.9
Out of an in‐depth study of a range of sulfinyl compounds in the transformation of alcohols into chloro alkanes emerged (2‐methoxyphenyl)methyl sulfoxide as optimal Lewis base catalyst. While this catalyst allowed the synthesis of benzylic chlorides in turn‐over numbers up to 50, aliphatic alcohols are non‐suitable substrates due to competing Pummerer rearrangement.
Mitsunobu Reaction Using Basic Amines as Pronucleophiles
作者:Hai Huang、Jun Yong Kang
DOI:10.1021/acs.joc.7b00622
日期:2017.7.7
reaction to include amine nucleophiles to form C–N bonds through the utilization of N-heterocyclic phosphine-butane (NHP-butane) has been developed. Both aliphatic alcohols and benzyl alcohols are suitable substrates for C–N bond construction. Various acidic nucleophiles such as benzoic acids, phenols, thiophenol, and secondary sulfonamide also provide the desired products of esters, ethers, thioether
Mechanically induced solvent-free esterification method at room temperature
作者:Lei Zheng、Chen Sun、Wenhao Xu、Alexandr V. Dushkin、Nikolay Polyakov、Weike Su、Jingbo Yu
DOI:10.1039/d0ra09437d
日期:——
Herein, we describe two novel strategies for the synthesis of esters, as achieved under high-speed ball-milling (HSBM) conditions at room temperature. In the presence of I2 and KH2PO2, the reactions afford the desired esterification derivatives in 45% to 91% yields within 20 min of grinding. Meanwhile, using KI and P(OEt)3, esterification products can be obtained in 24% to 85% yields after 60 min of
Ester Formation via Symbiotic Activation Utilizing Trichloroacetimidate Electrophiles
作者:Nivedita S. Mahajani、Rowan I. L. Meador、Tomas J. Smith、Sarah E. Canarelli、Arijit A. Adhikari、Jigisha P. Shah、Christopher M. Russo、Daniel R. Wallach、Kyle T. Howard、Alexandra M. Millimaci、John D. Chisholm
DOI:10.1021/acs.joc.9b00745
日期:2019.6.21
Trichloroacetimidates are useful reagents for the synthesis of esters under mild conditions that do not require an exogenous promoter. These conditions avoid the undesired decomposition of substrates with sensitive functional groups that are often observed with the use of strong Lewis or Brønsted acids. With heating, these reactions have been extended to benzyl esters without electron-donating groups. These inexpensive