Designing a catalytic synthesis of 4-methylcoumarin from ortho-iodophenyl 3-butenoate: Ring closure and isomerization control

Article abstract of DOI:10.1016/S0022-328X(96)06489-3

The palladium-catalyzed ring closure of ortho-iodophenyl 3-butenoate to 4-methylcoumarin is in competition with the isomerization to the 2-butenoic ester; the latter reaction has been controlled by the appropriate use of ligands, solvents and neutralizing agents to the point that quantitative yields of the cyclic compound have been attained.