We describe herein a highly stereoselective access to Cbz-protected β-enaminones 2 based on the NaOH catalyzed rearrangement of propargylichydroxylamines 1. The synthetic potential of these β-enaminones is illustrated in an original synthesis of pyrimidines.
Pd(II)-catalyzed ligand-controlled switching between cyclization-carbonylation and cyclization-carbonylation-cyclization-coupling (CCC-coupling) reactions of propargylic N-hydroxylamines was investigated. The use of a [Pd(tfa)2(box)] catalyst in MeOH afforded symmetric ketones bearing two 2,3-dihydroisoxazoles in good yields; replacing the catalyst and solvent with Pd(tfa)(2) and MeOH/DMSO led to the formation of methyl 2,3-dihydroisoxazole-4-carboxylates in good yields.