Three-component coupling using arynes and DMF: straightforward access to coumarins via ortho-quinone methides.

ortho-Quinone methides, arising from a formal [2+2] cycloaddition between arynes and DMF, were found to facilely undergo a [4+2] cycloaddition with ester enolates or ketenimine anions to produce diverse coumarins in a straightforward manner.