jo9821628_si_002.pdf (783.07 kB)
Synthesis of Isocoumarins and α-Pyrones via Palladium-Catalyzed Annulation of Internal Alkynes
journal contribution
posted on 1999-10-30, 00:00 authored by Richard C. Larock, Mark J. Doty, Xiaojun HanA number of 3,4-disubstituted isocoumarins and polysubstituted α-pyrones have been prepared in
good yields by treating halogen- or triflate-containing aromatic and α,β-unsaturated esters,
respectively, with internal alkynes in the presence of a palladium catalyst. Synthetically, the
methodology provides an especially simple and convenient, regioselective route to isocoumarins
and α-pyrones containing aryl, silyl, ester, tert-alkyl, and other hindered groups. The reaction is
believed to proceed through a seven-membered palladacyclic complex in which the regiochemistry
of the reaction is controlled by steric factors. A number of 3,4-disubstituted isocoumarins and
polysubstituted α-pyrones have been prepared in good yields by treating halogen- or triflate-containing aromatic and α,β-unsaturated esters, respectively, with internal alkynes in the presence
of a palladium catalyst. Synthetically, the methodology provides an especially simple and convenient
regioselective route to isocoumarins and α-pyrones containing aryl, silyl, ester, tert-alkyl, and other
hindered groups. The reaction is believed to proceed through a seven-membered palladacyclic
complex in which the regiochemistry of the reaction is controlled by steric factors.