The diastereoselective electrochemical carboxylation of chiral N-(2-bromoacyl)oxazolidin-2-ones has been studied. This reaction was carried out by cathodic reduction of the C-Br bond, in the presence of carbon dioxide, followed by treatment with diazomethane. The yields and the diastereomeric ratio of the two epimeric alkylmalonic acid derivatives are strongly affected by various factors: solvent-supporting electrolyte system, temperature, electrode material, electrolysis conditions, oxazolidinone moiety. The higher yields (88%) were obtained starting from N-(2-bromopropionyl)4R-phenyloxazolidin-2-one la, but with poor diastereoselectivity (61:39). The two epimers were easily separated by flash chromatography. The best results were achieved using a different chiral auxiliary: Oppolzer's camphor sultam. Starting from 1j a good yield in carboxylated product was obtained (80%) with excellent diastereoselectivity (98:2). These chiral alkylmalonic acid derivatives are valuable building blocks in the synthesis of molecules with biological activity and of chiral propane-1,3-diols derivatives.
FEROCI M., ORSINI M., PALOMBI L., SOTGIU G, COLAPIETRO M., & INESI A. (2004). Diastereoselective electrochemical carboxylation of chiral ?-bromocarboxylic acid derivatives: an easy access to unsymmetrical alkylmalonic ester derivatives. JOURNAL OF ORGANIC CHEMISTRY, 69(2), 487-494 [10.1021/jo0343836].
Diastereoselective electrochemical carboxylation of chiral ?-bromocarboxylic acid derivatives: an easy access to unsymmetrical alkylmalonic ester derivatives
SOTGIU, Giovanni;
2004
Abstract
The diastereoselective electrochemical carboxylation of chiral N-(2-bromoacyl)oxazolidin-2-ones has been studied. This reaction was carried out by cathodic reduction of the C-Br bond, in the presence of carbon dioxide, followed by treatment with diazomethane. The yields and the diastereomeric ratio of the two epimeric alkylmalonic acid derivatives are strongly affected by various factors: solvent-supporting electrolyte system, temperature, electrode material, electrolysis conditions, oxazolidinone moiety. The higher yields (88%) were obtained starting from N-(2-bromopropionyl)4R-phenyloxazolidin-2-one la, but with poor diastereoselectivity (61:39). The two epimers were easily separated by flash chromatography. The best results were achieved using a different chiral auxiliary: Oppolzer's camphor sultam. Starting from 1j a good yield in carboxylated product was obtained (80%) with excellent diastereoselectivity (98:2). These chiral alkylmalonic acid derivatives are valuable building blocks in the synthesis of molecules with biological activity and of chiral propane-1,3-diols derivatives.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
