Knöevenagelreactions of aldehydes and ketones with malononitrile, isopropyl cyanoacetate and diisopropyl malonate catalyzed by Ti(O-i-Pr)4 proceeded smoothly in i-PrOH to give the corresponding reaction products in good to high yield. 3-Substituted coumarins were prepared by the present method.
Three-component coupling using arynes and DMF: straightforward access to coumarins via ortho-quinone methides
作者:Hiroto Yoshida、Yu Ito、Joji Ohshita
DOI:10.1039/c1cc11955a
日期:——
ortho-Quinone methides, arising from a formal [2+2] cycloaddition between arynes and DMF, were found to facilely undergo a [4+2] cycloaddition with ester enolates or ketenimine anions to produce diverse coumarins in a straightforward manner.
KPF<sub>6</sub>-Mediated Esterification and Amidation of Carboxylic Acids
作者:Sonam、Vikki N. Shinde、Anil Kumar
DOI:10.1021/acs.joc.1c02611
日期:2022.3.4
been developed for the synthesis of esters and amides. A wide range of carboxylicacids and alcohols or amines worked well under the developed reaction conditions, thus providing good to excellent (61–98%) yields of the corresponding esters and amides. The method worked well with bioactive substrates such as cholesterol, levulinic acid, and linoleic acid. Wide substrate scope, operational simplicity
Enantioselective Synthesis of 4-Substituted Dihydrocoumarins through a Zinc Bis(hydroxyamide)-Catalyzed Conjugate Addition of Terminal Alkynes
作者:Gonzalo Blay、M. Carmen Muñoz、José R. Pedro、Amparo Sanz-Marco
DOI:10.1002/adsc.201201120
日期:2013.4.15
A new enantioselective catalyst for the conjugateaddition of terminalalkynes has been developed. Terminalalkynes react with 3‐alkoxycarbonylcoumarins in the presence of diethylzinc and bis(hydroxyamide) ligands to give chiral non‐racemic dihydrocoumarins substituted with an alkynyl group on the C‐4 position with good yields and enantiomeric excesses up to 95%.
Redox activated amines in the organophotoinduced alkylation of coumarins
作者:Shashank Singh、Krishna N. Tripathi、Ravi P. Singh
DOI:10.1039/d2ob00943a
日期:——
represents the quintessential scaffold of many natural products. While C-3 alkylation is easily achievable, effective greener strategies for C-4 alkylation have been less forthcoming. Herein, we report a metal-free photoinduced deaminative strategy for C-4 alkylation of coumarins using redox activated secondary and benzylic amine derived Katritzky pyridinium salts.