The Synthesis of 5-, 6-, 7- and 8-Membered Oxygen-containing Benzo-fused Rings using Alkene Isomerization and Ring-closing Metathesis Reactions

A number of benzo-fused oxygen-containing heterocycles were synthesized from allyl-3-isopropoxy-4-methoxybenzaldehyde using metathesis or an alkene isomerization-metathesis sequence as key synthetic steps. Benzo-fused compounds thus formed included a 3, 6-dihydro-1H-2-benzoxocine, 1, 3-dihydro-benzo[c]oxepine, 1H-isochromene, 2, 3-dihydro-benzo[b]oxepine, benzofuran and 2H-chromene skeleton, demonstrating the versatility of this methodology.