Versatile Methodology to Synthesize Oxygen‐Bridged Nine‐ and Ten‐Membered Cycloalkanes by the Hypoiodite Reaction

Abstract

C‐3 derivatives of 6‐hydroxy‐2,7‐dimethyl‐11‐oxatricyclo[6.2.1.02,6]undecan‐4‐one reacted with lead tetraacetate (LTA) and iodine to afford, in good yield, 1,7‐epoxycyclononanes, which are the result of a β‐fragmentation of the C2–C6 bond adjacent to the tertiary hydroxy group on C‐6. This β‐fragmentation is followed by a ring contraction from a ten‐ to a nine‐membered ring system, by a free‐radical addition to the carbonyl group on C‐4. The reaction of precursors (not functionalized on C‐3) with LTA and iodine produced a β‐fragmentation without any further structural rearrangement, affording 1,8‐epoxycyclodecanes. The transformation of the carbonyl group on C‐4 to acetate avoided radical additions and rearrangements affording, in high yield, the corresponding cyclodecanes. By this methodology, either 1,7‐epoxycyclononane or 1,8‐epoxycyclodecane could be synthesized, in good yield, by choosing the appropriate substitution pattern on C‐3 in the substrate.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)