N-Alkylation of N-arylsulfonyl-α-amino acid methyl esters by trialkyloxonium tetrafluoroborates |
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Authors: | Rosaria De MarcoMaria Luisa Di Gioia Angelo Liguori Francesca PerriCarlo Siciliano Mariagiovanna Spinella |
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Institution: | Dipartimento di Scienze Farmaceutiche, Università della Calabria, Edificio Polifunzionale, I-87036 Arcavacata di Rende (CS), Italy |
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Abstract: | In this work we present the results obtained for the N-alkylation of a series of N-arylsulfonyl-α-amino acid methyl esters bearing different substituents at the 4-position of the sulfonamide aromatic ring. In particular, we compare the reactivity of these species with diazomethane and trimethyloxonium tetrafluoroborate in N-methylation processes. Diazomethylation is unsuccessful for N-arylsulfonamide derivatives containing electron-releasing groups on the aromatic ring. In these cases trimethyloxonium tetrafluoroborate is the reagent of choice for the direct and quantitative N-methylation. Further we extend our evaluation to the use of triethyloxonium tetrafluoroborate. This reagent shows to be very efficient in order to prepare N-ethyl derivatives of N-arylsulfonyl-α-amino acid methyl esters. An experimental protocol similar to that used for N-methylation with trimethyloxonium tetrafluoroborate is applied for the N-ethylation. |
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Keywords: | Amino acids N-Alkylation N-Arylsulfonamides Trimethyloxonium tetrafluoroborate Triethyloxonium tetrafluoroborate |
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