N-Heterocyclic Carbene-Mediated Oxidative Esterification of Aldehydes: Ester Formation and Mechanistic Studies
摘要:
An unexpected N-heterocyclic carbene-catalyzed esterification of alpha,beta-unsaturated aldehydes including aromatic aldehydes with reactive cinnamyl bromides in the presence of air oxygen or MnO2 as an oxidant is described. In the presence of oxygen, halogenated and electron-deficient aldehydes react smoothly to furnish esters in good yields. Great efforts have been made on mechanistic studies to deduce a plausible mechanism, based on the experimental results and isotopic labeling experiment.
Synthesis of Enantioenriched Bromohydrins via Divergent Reactions of Racemic Intermediates from Anchimeric Oxygen Borrowing
作者:Yi-Ming Cao、Dieter Lentz、Mathias Christmann
DOI:10.1021/jacs.8b06432
日期:2018.8.29
catalyzed bromocyclization/regiodivergent reaction of racemic intermediates sequence, which is enabled by anchimeric oxygen borrowing. Different types of alkenes are applicable, and both enantiomers of the bromohydrin products were obtained in generally excellent yields and enantioselectivities. In addition, an example of enantioconvergentsynthesisfrom the two isomeric products is presented.
Copper-Catalyzed Cross-Coupling of Thiols, Alcohols, and Oxygen for the Synthesis of Esters
作者:Seungyeon Lim、Miran Ji、Xi Wang、Chan Lee、Hye-Young Jang
DOI:10.1002/ejoc.201403311
日期:2015.1
Copper-catalyzed, one-pot, three-component coupling reactions using thiols, alcohols, and oxygen to form a variety of esters in good yields were studied. In the presence of easily oxidized benzylic and allylic alcohols, thiols were selectively oxidized to form thionoesters, which underwent facile S/O exchange to afford esters. Thiols may be used as an alternative benzoyl source under mild aerobic conditions
Palladium-Catalyzed Selective Anti<i>-</i>Markovnikov Oxidation of Allylic Esters
作者:Jia Jia Dong、Martín Fañanás-Mastral、Paul L. Alsters、Wesley R. Browne、Ben L. Feringa
DOI:10.1002/anie.201301809
日期:2013.5.17
An aldol alternative: The palladium(II)‐catalyzed anti‐Markovnikov oxidation of allylicesters to aldehydes at room temperature provides a viable alternative to valuable cross aldol products. High regioselectivity towards the aldehyde product was achieved using the ester protecting group for the allylic alcohol. Rapid isomerization and the much higher rate of oxidation of the branched isomer result