反应详情

Scheme 2 provides an alternative synthesis of C-3 substituted 4-hydroxycoumarins when R1 is aryl groups. 4-hydroxycoumarin and an aromatic aldehyde can be heated in a mixture of triethylamine and formic acid (2:5 molar ratio) to give 3-benzyl-4-hydroxycoumarin, which was in turn treated with 2.2 eq. of BuLi and quenched with carbon dioxide to give coumarin substituted phenyl-acetic acid. Corresponding esters can be obtained by treating the acid with various alcohols in the presence of concentrated sulfuric acid.

1. customScheme 2 provides