Phosphoric Acid Catalyzed Aldehyde Addition to in Situ Generated <i>o</i>-Quinone Methides: An Enantio- and Diastereoselective Entry toward <i>cis</i>-3,4-Diaryl Dihydrocoumarins
作者:Matthias Spanka、Christoph Schneider
DOI:10.1021/acs.orglett.8b01865
日期:2018.8.17
phosphoric acid catalyzed synthesis of cis-3,4-diarylchromanols through reaction of o-hydroxybenzhydryl alcohols and aryl acetaldehydes is reported. The products can be further manipulated to 3,4-dihydrocoumarins, 4H-chromenes, and chromanes with good overall yields and very good diastereo- and enantiocontrol. This reaction is based upon the concept of enol catalysis and comprises the in situ generation
Organocatalytic Asymmetric Domino Michael/Acyl Transfer Reaction Between <i>α</i>
-Nitroketones and <i>in situ-</i>
Generated <i>ortho</i>
-Quinone Methides: Route to 2-(1-Arylethyl)phenols
作者:Chandan Gharui、Debasmita Behera、Subhas Chandra Pan
DOI:10.1002/adsc.201801015
日期:2018.12.3
organocatalytic asymmetric domino Michael/acyl transfer reaction between α‐nitroketones and o‐quinone methides is disclosed. o‐Quinone methides are generated in situ from 2‐sulfonylmethylphenols in basic medium. With 10 mol% of bifunctional squaramide catalyst, high yields and excellent enantioselectivities are achieved for a variety of O‐acyl 2‐(1‐arylethyl)phenols under mild reaction condition.
Microwave-Assisted Generation and Capture by Azoles of<i>ortho</i>-Quinone Methide Intermediates under Aqueous Conditions
作者:Silvia González-Pelayo、Luis A. López
DOI:10.1002/ejoc.201701183
日期:2017.11.2
ortho-Quinone methides can be efficiently generated in water. Trapping with azoles provides a convenient route to alkylated azole derivatives, a class of heterocyclic compounds with potential applications in medicinal chemistry. This protocol does not require any activator for the generation of the reactiveintermediate. No chromatographic purification is required in most cases.
An expeditious and highly practical, microwave assisted benzylation of naphthols and 4-hydroxycoumarin has been developed under catalyst-free & solvent-free conditions. Alcohols undergo heat induced dehydration to form ethers, which collapse reversibly to form the carbocation which was captured immediately by a suitable nucleophile to furnish the benzylated compounds.