| Popis: |
In the first part of this work we developed four novel methodologies for the generation of nitroso dienophile from commercially available hydroxamic acid I which is trapped with appropriate diene through a hetero-Diels-Alder (HDA) reaction (Scheme 1). These procedures afforded cycloadduct in good yields, employing reagents in a 1:1 ratio and only 5 mol.% catalyst loading. Remarkably, the crude reaction mixture showed the HDA adduct as the only compound present: this renders the reactions described herein as ideal for the development of tandem processes. Moreover, we demonstrated that these new methodologies can be applied to a large number of dienes. In the second part we demonstrated the synthetic usefulness of styrylisoxazole IV which was used to access a number of compounds. Herein we describe the syntheses of aziridines V, N-Michael adducts VI, VII and VIII and S-Michael adducts IX which were obtained by reacting styrylisoxazole IV, with the corresponding nucleophile (Scheme 2). We also report the one-pot preparation of S-Michael adducts IX from commercially available isoxazole X, an aromatic aldehyde XI and benzyl mercaptan XII (Scheme 3). |
