First attempts at differential diastereoselection in catalytic reactions of N-chirally substituted dirhodium(ii) tetrakis[methyl 2-oxoimidazolidine-4(S)-carboxylates] with diazoacetates |
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Authors: | Doyle M P Timmons D J Arndt M M R Duursma A Colyer J T Brünner H |
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Institution: | (1) University of Arizona, 85721 Arizona, Tucson, USA;(2) University of Regensburg, 93040 Regensburg, Germany |
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Abstract: | Chiral attachments on 2-oxoimidazolidine-4(S)-carboxylate ligands for dirhodium(ii) can provide differential diastereoselection in catalytic reactions of diazo compounds. The synthesis of these heterocyclic ligands from the readily available amino acid asparagine is reported. Reactions with diazoacetates offering intramolecular carbon—hydrogen insertion provide evaluative data that demonstrate differential diastereoselection. Surprisingly, placement of a carbonyl group within the chiral attachment removes enantiocontrol from the catalyst, presumably because of intramolecular ylide formation. |
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Keywords: | chiral dirhodium(ii) catalysts catalysis N-acylimidazolidinone-carboxylates asymmetric carbon— hydrogen insertion metal carbene reactions |
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