o-methoxyaryl-aldehydes (or -ketones) react in solid-phase with Meldrum's acid under mild conditions, to give benzylidene derivatives which are cyclized in high yield, with cold sulfuric acid to substituted 3-carboxycoumarins. Thermal decarboxylation, speed up by copper powder, provided an easy access to numerous coumarins.
o-methoxyaryl-aldehydes (or -ketones) react in solid-phase with Meldrum's acid under mild conditions, to give benzylidene derivatives which are cyclized in high yield, with cold sulfuric acid to substituted 3-carboxycoumarins. Thermal decarboxylation, speed up by copper powder, provided an easy access to numerous coumarins.
o-methoxyaryl-aldehydes (or -ketones) react in solid-phase with Meldrum's acid under mild conditions, to give benzylidene derivatives which are cyclized in high yield, with cold sulfuric acid to substituted 3-carboxycoumarins. Thermal decarboxylation, speed up by copper powder, provided an easy access to numerous coumarins.