Synthesis of Benzofuranones
An effective Pd-catalyzed hydroesterification of alkenylphenols with phenyl formate as CO surrogate enables the synthesis of various lactones in generally high yields with high regioselectivities. In one case, 76% ee is obtained with a chiral ligand.
H. Wang, B. Dong, Y. Wang, J. Li, Y. Shi, Org. Lett., 2014, 16, 186-189.
Pd(II)-catalyzed C-H activation of phenylacetic acids followed by an intramolecular C-O bond formation afforded benzofuranones. A modified reaction provides the first example of enantioselective C-H functionalizations through Pd(II)/Pd(IV) redox catalysis.
X.-F. Cheng, Y. Li, Y.-M. Su, F. Yin, J.-Y. Wang, J. Sheng, H. U. Vora, X.-S. Wang, J.-Q. Yu, J. Am. Chem. Soc., 2013, 135, 1236-1239.
An efficient TfOH-catalyzed cascade ortho C-H activation/lactonization of phenols with α-aryl-α-diazoacetates provides an operationally simple and rapid method for the one-pot assembly of diverse α-aryl benzofuranones in high yields. This metal-free protocol offers broad substrate scope, good chemo/regioselectivity, and excellent functional group compatibility.
S. Hu, Z. Lu, M. Liu, H. Xu, J. Wu, F. Chen, J. Org. Chem., 2020, 85, 14916-14925.
A metal-free tandem Friedel-Crafts/lactonization reaction to 3,3-diaryl or 3-alkyl-3-aryl benzofuranones is catalyzed by HClO4. The reaction of various tertiary α-hydroxy acid esters with substituted phenols affords the desired products in rich diversity. 1H NMR studies supports that this tandem reaction proceeds via tandem Friedel-Crafts/lactonization sequence.
L. Chen, F. Zhou, T.-D. Shi, J. Zhou, J. Org. Chem., 2012, 77, 4354-4362.