Annulated Isoxazoles via [3 + 2] Cycloaddition of Alkenyl Bromides and Oximoyl Chlorides and Ag(I) Promoted Elimination

Substituted
salicylaldehydes are converted to fused tetracyclic
isoxazoles through a synthetic sequence incorporating substitution
of 2-bromo-2-cyclohexen-1-ol, formation of an oxime function, conversion
to an oximoyl chloride, intramolecular [3 + 2] cycloaddition, and
elimination of an equivalent of hydrogen bromide using silver­(I) carbonate.
Six examples of this sequence are presented.