Synthesis of carboxylic amides by ring-opening of oxazolidinones with Grignard reagents |
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Authors: | Bensa David Coldham Iain Feinäugle Pia Pathak Ravindra B Butlin Roger J |
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Institution: | Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, S3 7HF, UK. |
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Abstract: | Treatment of N-alkyl-oxazolidin-2-ones with Grignard reagents gives tertiary carboxylic amide products. Various substituted oxazolidinones can be used as illustrated with phenyl, benzyl or isopropyl groups on the 4-position, and methyl, benzyl or p-methoxybenzyl groups on the 3-position (the nitrogen atom). A selection of Grignard reagents were successful, including allyl, benzyl, alkyl and phenyl magnesium halides. The organomagnesium species attacks the carbonyl group and promotes ring-opening of the oxazolidinone. The product tertiary amides are useful substrates for stereoselective transformations and were applied to a highly selective enolate alkylation and to a ring-closing metathesis reaction to a six-membered lactam and hence a formal synthesis of the alkaloids (-)-coniine and (+)-stenusine. |
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