Decarboxylative cross-coupling and applications thereof
Methods described herein enable the production of numerous molecular species through decarboxylative cross-coupling via use of photoredox and transition metal catalysts. A method described herein, in some embodiments, comprises providing a reaction mixture including a photoredox catalyst, a transition metal catalyst, a coupling partner and a substrate having a carboxyl group. The reaction mixture is irradiated with a radiation source resulting in cross-coupling of the substrate and coupling partner via a mechanism including decarboxylation, wherein the coupling partner is selected from the group consisting of a substituted aromatic compound and a substituted aliphatic compound.
1. A method of cross-coupling comprising:
providing a reaction mixture comprising a photoredox catalyst, a transition metal catalyst, a coupling partner and a substrate having a carboxyl group; and
irradiating the reaction mixture with a radiation source resulting in cross-coupling of the substrate and coupling partner via a mechanism including decarboxylation, wherein the coupling partner is selected from the group consisting of a substituted aromatic compound and a substituted aliphatic compound.
2. The method of claim 1 , wherein the photoredox catalyst is a transition metal complex.
3. The method of claim 2 , wherein the transition metal complex is an iridium complex or a ruthenium complex.
4. The method of claim 2 , wherein the transition metal complex is a heteroleptic iridium complex.
5. The method of claim 4 , wherein the heteroleptic iridium complex is selected from the group consisting of Ir[dF(CF 3 )ppy] 2 (dtbbpy) + , Ir(ppy) 2 (dtbbpy) + and Ir[dF(5-Me)ppy] 2 (tetraMePhen) + .
6. The method of claim 1 , wherein decarboxylation forms an alkyl radical.
7. The method of claim 1 , wherein the substrate is an aliphatic carboxylic acid.
8. The method of claim 7 , wherein the aliphatic carboxylic acid is an N-protected proline.
9. The method of claim 7 , wherein the aliphatic carboxylic acid is a fatty acid.
10. The method of claim 7 , wherein the aliphatic carboxylic acid is of formula R 1 —CO 2 H, wherein R 1 is selected from the group consisting of -alkyl, -cycloalkyl, -heteroalkyl, -heterocycloalkyl, -alkenyl, -cycloalkenyl, -heteroalkenyl, -heterocycloalkenyl, -alkynyl, -alkyl-aryl, -alkyl-heteroaryl, -alkyl-alkoxy, -alkenyl-aryl, -alkenyl-heteroaryl, -cycloalkyl-aryl, -cycloalkyl-heteroaryl, -cycloalkenyl-aryl, -heterocycloalkenyl-aryl, and -alkenyl-alkoxy.
11. The method of claim 1 , wherein the substrate is a keto acid.
12. The method of claim 11 , wherein the keto acid is an aliphatic keto acid.
13. The method of claim 11 , wherein the keto acid is an aryl keto acid or heteroaryl keto acid.
14. The method of claim 11 , wherein the keto acid is of the formula R 2 —C(O)—CO 2 H, wherein R 2 is selected from the group consisting of -alkyl, -cycloalkyl, -heteroalkyl, -heterocycloalkyl, -alkenyl, -cycloalkenyl, -heteroalkenyl, -heterocycloalkenyl, -alkynyl, -aryl, -heteroaryl, -alkyl-aryl, -alkyl-heteroaryl, -alkyl-alkoxy, -alkenyl-aryl, -alkenyl-heteroaryl and -alkenyl-alkoxy.
15. The method of claim 1 , wherein the cross-coupling is a sp 3 -sp 2 cross-coupling.
16. The method of claim 1 , wherein the cross-coupling is a sp 3 -sp 3 cross-coupling.
17. The method of claim 1 , wherein the substituted aromatic compound is a substituted aryl or substituted heteroaryl.
18. The method of claim 17 , wherein the substituted aryl is an iodo-aryl compound.
19. The method of claim 1 , wherein the substituted aliphatic compound comprises one or more points of unsaturation.
20. The method of claim 1 , wherein the substituted aliphatic compound is saturated.
21. The method of claim 20 , wherein the substituted aliphatic compound comprises a halide leaving group.
22. The method of claim 1 , wherein the carboxyl group of the substrate is in protonated form, deprotonated form, salt form or a carboxylate ester.
23. The method of claim 1 , wherein the mechanism comprises formation of a radical followed by decarboxylation.
24. The method of claim 23 , wherein the formation of the radical includes a single electron transfer process.
25. The method of claim 23 , wherein the radical is a carboxyl radical.
26. The method of claim 24 , wherein the single electron transfer process involves single electron transfer between a transition metal and the substrate.
27. The method of claim 24 , wherein the single electron transfer process involves single electron transfer between photoredox catalyst and the substrate.
28. The method of claim 1 , wherein the photoredox catalyst and transition metal catalyst engage in a single electron transfer process.