Research paperNew insights into the alkoxycarbonylation of propargyl alcohol

- Propargyl alcohol carbonylation is efficiently catalyzed by Drent's catalyst.
- The selectivity towards alkyl 2-(hydroxymethyl)acrylates is >99%.
- Turnover frequency numbers >450 h−1 are obtained under mild conditions.
- The mechanism of catalyst deactivation has been determined.

The challenging carbonylation of propargyl alcohol is effectively catalyzed by Pd(OAc)2 in combination with diphenyl-(6-methyl-pyridin-2-yl)phosphine and methanesulfonic acid. In dichloroethane at 20-50 °C, the reaction affords with almost complete regioselectivity alkyl 2-(hydroxymethyl)acrylates. Turnover frequency numbers (TOF) of up to 450 h−1 can be achieved working at 50 °C, while a maximum turnover number (TON) of about 730 is obtained at 30 °C. The catalyst longevity is limited because the carbonylation product reacts with the phosphorus atom of the ligand to give a quaternary phosphonium salt. This reaction leads to deactivation of the catalyst and eventually to palladium black formation.