N-O Cleavage reactions of heterobicycloalkene-fused 2-isoxazolines.

Transition metal-mediated N-O bond cleavage reactions of heterobicycloalkene-fused 3-methyl-2-isoxazolines were investigated. Optimal cleavage conditions were found with Raney nickel/AlCl3 mediation in aqueous methanol. The reaction provided a diverse collection of novel heterobicycle-fused β-hydroxyketones with good to excellent yields (66-95%) and without the need for chromatographic purification.

1-(3-Hy-droxy-5,8-dimeth-oxy-4-methyl-1,2,3,4-tetra-hydro-1,4-ep-oxy-naphthalen-2-yl)ethan-1-one.

The stereochemistry and regioschemistry (exo) of the title compound, C15H18O5, were determined by the X-ray analysis. The meth-oxy groups essentially lie in the plane of the benzene ring to which they are attached, as described by the C-O-C C torsion angles of -176.80 (12) and 4.

5,8-Dimeth-oxy-3,9-dimethyl-3a,4,9,9a-tetra-hydro-4,9-ep-oxy-naphtho-[2,3-d]isoxazole.

The title compound, C15H17NO4, is the exo isomer with a syn arrangement of the O atom in the isoxazole ring to the methyl group of the bicyclic alkene. The dihedral angle between the isoxazole ring and the benzene ring is 7.42 (9)°.

(3-Methyl-3a,4,7,7a-tetra-hydro-5H-4,7-methano-isoxazolo[4,5-d][1,2]oxazin-5-yl)(phen-yl)methanone.

The title compound, C14H14N2O3, is the exo isomer with a syn arrangement of two O atoms in the isoxazole and oxazine rings. The dihedral angle between the isoxazole and phenyl rings is 60.38 (4)°.