Abstract
The PdII-assisted cycloadditions of nitrones to nitriles give the corresponding fused tricyclic fluorinated ketoimine, bicyclic or monocyclic Δ4-1,2,4-oxadiazoline PdII complexes. The free tetrafluoro-2,3-dihydropyrrolo[1,2-a]quinazolin-5-one and Δ4-1,2,4-oxadiazolines are liberated upon reaction of the PdII complexes with dppe. [Display omitted]
•Palladium(II)-assisted cycloaddition of nitrones to nitriles.•Pyrroline N-oxide/nitrile coupling.•Acyclic nitrone/nitrile coupling.•Liberation of N-heterocyclic ligands by displacement with dppe.
The [2+3] cycloadditions of different organonitriles NCR (R1=C6F5, R2=Pr, R3=p-CHOC6H4, R4=Ph) with the cyclic nitrone ▪ or acyclic nitrone −O+N(Me)C(H)(C6H2Me3-2,4,6), in the presence of PdCl2, give the corresponding fused tricyclic fluorinated ketoimine trans-▪ (1), fused bicyclic Δ4-1,2,4-oxadiazoline trans-▪ (R2=Pr (2), R3=p-CHOC6H4 (3)) or monocyclic Δ4-1,2,4-oxadiazoline trans-▪ (4) palladium(II) complexes. The free tetrafluoro-2,3-dihydropyrrolo[1,2-a]quinazolin-5-one (1a) and Δ4-1,2,4-oxadiazolines (2a–4a) are liberated upon reaction of complexes 1–4 with a diphosphine (dppe). All the compounds were characterized by elemental analyses, ESI+-MS, IR, 1H and 13C NMR spectroscopies.