Metal-catalyzed alkoxycarbonylation of a lactone
The metal-catalyzed alkoxycarbonylation of a lactone is a method of alkoxycarbonylating a δ-lactone, specifically 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one. The method includes combining the δ-lactone with an alcohol in an organic solvent in the presence of a catalyst system that includes palladium or a salt thereof to form a reaction mixture, which is heated to 110-130° C. at a pressure of 20-50 bar for between 3-5 hours under flow of carbon monoxide gas. The product of the reaction is a substituted 2-octendioate diester. The alcohol may be methyl alcohol, n-butyl alcohol, 2-ethylhexanol, isobutyl alcohol, isopropyl alcohol, benzyl alcohol, or phenol. The solvent may be toluene, acetonitrile, or tetrahydrofuran. The method may include adding an acid to the reaction mixture, which may be dilute (about 5 mol %) sulfuric or p-toluenesulfonic acid. The catalyst system may also include a phosphine ligand.
1. A method for metal-catalyzed alkoxycarbonylation of a δ-lactone, the δ-lactone being 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, the method comprising the steps of:
adding an alcohol and a catalyst system including palladium or a salt thereof to a solution of the δ-lactone in an organic solvent to form a reaction mixture, wherein the catalyst system further comprises a phosphine ligand having the formula:
placing the reaction mixture under pressure of carbon monoxide (CO) gas;
heating the reaction mixture to a temperature of at least 110° C.; and
recovering a 2-octendioate diester product.
2. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , further comprising a step of adding an acid to the reaction mixture.
3. The method for metal-catalyzed alkoxycarbonylation according to claim 2 , wherein the acid is selected from the group consisting of p-toluenesulfonic acid, methanesulfonic acid, hydrochloric acid, and sulfuric acid.
4. The method for metal-catalyzed alkoxycarbonylation according to claim 2 , wherein the acid is p-toluenesulfonic acid.
5. The method for metal-catalyzed alkoxycarbonylation according to claim 2 , wherein the acid is sulfuric acid.
6. The method for metal-catalyzed alkoxycarbonylation according to claim 2 , wherein the acid is diluted to 5 mol %.
7. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , wherein the solvent is selected from the group consisting of toluene, acetonitrile, and tetrahydrofuran.
8. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , wherein the step of heating the reaction mixture comprises heating the reaction mixture to 110-130° C.
9. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , wherein the step of placing the reaction mixture under pressure carbon monoxide gas comprises placing the reaction mixture under pressure of at least 20 bar CO.
10. The method for metal-catalyzed alkoxycarbonylation according to claim 9 , wherein the pressure is 20-50 bar CO.
11. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , wherein the step of heating the reaction mixture is carried out for at least three hours.
12. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , wherein the step of heating the reaction mixture is carried out for three to five hours.
13. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , wherein the alcohol is selected from the group consisting of methyl alcohol, n-butyl alcohol, 2-ethylhexanol, isobutyl alcohol, isopropyl alcohol, benzyl alcohol, and phenol.
14. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , further comprising a step of heating the 2-octendioate diester product in tetrahydrofuran solvent in the presence of a Pd/C catalyst and under flow of hydrogen gas in order to obtain a saturated diester product.
15. The method for metal-catalyzed alkoxycarbonylation according to claim 1 , further comprising a step of reacting the 2-octendioate diester product with bis(trifluoromethane)sulfonimide (HNTf 2 ) in the presence of ruthenium acetylacetonate/1,1,1-tris-(diphenylphosphinomethyl)ethane catalyst under pressure of hydrogen gas to obtain a saturated diol product.
16. An alkoxycarbonylated δ-lactone having the formula:
wherein R is selected from the group consisting of methyl, n-butyl, 2-ethylhexanyl, isobutyl, isopropyl, benzyl, and phenyl.