Processes for converting carboxamides to thiocarboxamides
Process for converting a carboxamide to a thiocarboxamide includes reacting (a) a substrate that comprises a heteroatom-containing moiety and a carboxamide moiety with (b) a dialkyl dithiophosphate and/or a salt thereof. The heteroatom-containing moiety includes a heteroatom selected from the group consisting of N, O, and S. Processes for preparing piperidine-4-thiocarboxamide are described.
1. A process for preparing piperidine-4-thiocarboxamide comprising:
reacting piperidine-4-carboxamide with di-(2-methoxyethyl) dithiophosphate and/or a salt thereof in an aromatic solvent.
2. The process of claim 1 , wherein the aromatic solvent is toluene.
3. The process of claim 1 , wherein the process further comprises:
forming the di-(2-methoxyethyl) dithiophosphate by reacting 2-methoxyethanol with P 4 S 10 .
4. The process of claim 3 , wherein the step of forming is performed in toluene.
5. The process of claim 3 , wherein the step of reacting the piperidine 4-carboxamide comprises adding the piperidine-4-carboxamide to the formed di-(2-methoxyethyl) dithiophosphate in the aromatic solvent.
6. The process of claim 1 , wherein the step of reacting is performed at a temperature of about 60° C. to about 125° C.
7. The process of claim 6 , wherein the step of reacting is performed at a temperature of about 105° C. to about 115° C.
8. The process of claim 1 , wherein the step of reacting is performed at the reflux temperature of the aromatic solvent.
9. The process of claim 1 , wherein the di-(2-methoxyethyl) dithiophosphate is used in a molar excess relative to the piperidine-4-carboxamide.
10. The process of claim 9 , wherein the molar excess is about 2.1 equivalents to about 3 equivalents relative to the piperidine-4-carboxamide.