Tetramic acid and imidazolidinone syntheses via unexpected base induced cyclisations of alanine derived Weinreb amides

Gibson, Colin and Kennedy, A.R. and Morthala, R.R. and Parkinson, J.A. and Suckling, C.J. (2008) Tetramic acid and imidazolidinone syntheses via unexpected base induced cyclisations of alanine derived Weinreb amides. Tetrahedron, 64 (32). pp. 7619-7625. ISSN 0040-4020 (https://doi.org/10.1016/j.tet.2008.05.058)

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Abstract

Reactions of N-protected derivatives of Weinreb amides of alanine with strong base unexpectedly gave tetramic acid derivatives or an imidazolidinone. The tetramic acid derivatives were obtained by unusual cyclisation of N-acyl N-methoxy derivatives of alanine Weinreb amide upon treatment with potassium hexamethyldisilazide and benzyl bromide. In contrast, treatment of a bromobenzylidine alanine Weinreb amide with potassium hexamethyldisilazide gave rise to cyclisation to form an imidazolidinone.