Unprecedented reactivity pattern of chromium fischer carbene complexes. Direct application to one-pot synthesis of 4-aryl-3,4-dihydrocoumarins on a multigram scale.

[reaction: see text] Reaction of alkenyl carbene chromium(0) complexes and ketene acetals triggers the formation of 4-aryl-3,4-dihydrocoumarins. The reaction can be carried out as a simple one-pot protocol in air atmosphere. The huge interest of dihydrocoumarins has prompted us to optimize a multigram-scale process.