Lithiation in flavones, chromones, coumarins, and benzofuran derivatives was written by Costa, Ana M. B. S. R. C. S.;Dean, Francis M.;Jones, Michael A.;Varma, Rajender S.. And the article was included in Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999) in 1985.Reference of 1646-27-1 This article mentions the following:
Flavones were lithiated in the 3-position by LiN(CHMe2)2 in THF at -78° to give stable derivatives which were readily converted to the corresponding carboxy, ethoxycarbonyl, mercapto, methylthio, trimethylsilyl, hydroxy, or other derivatives E.g., treatment of flavone with LiN(CHMe2)2 in THF at -78° gave 3-lithioflavone which reacted with CO2 to give 92% 3-flavonecarboxylic acid. Benzofurans were preferentially lithiated at the 2-position; where this was blocked lithiation occurred in the 3-position in the presence of an activating group. Ring-opening of benzofurans occurred in some cases giving acetylenic phenols directly. Chromenes were lithiated at positions 2 and 3, depending on substitution. Coumarins generally behaved as esters and gave the corresponding amides with LiN(CHMe2)2, except for 4-methoxycoumarin which underwent lithiation in the 3-position. Deprotonation in the 32-position in ethers occurs easily only when there is an ether link antiperiplanar to the proton removed. The lithiated species are really unstable intermediates in trans eliminations leading to alkyne derivatives In the experiment, the researchers used many compounds, for example, Methyl benzofuran-2-carboxylate (cas: 1646-27-1Reference of 1646-27-1).
Methyl benzofuran-2-carboxylate (cas: 1646-27-1) belongs to benzofurans derivatives. Benzofurans are compounds with a planar structure having 10 pi electrons that include the lone pair on oxygen atom, which makes it more susceptible to electrophilic attack. Benzofurans have also made significant and distinctive contributions to biology. They exhibit several biological activities that range from antioxidant, antitubercular, antiplasmodial, insecticidal.Reference of 1646-27-1
Referemce:
Benzofuran – Wikipedia,
Benzofuran | C8H6O – PubChem