New Synthetic Methods for Seven- and Eight-Membered Cyclic Ethers Based on the Ring-Expansion Reactions of Hydroxy or Lithioxy Methoxyallenylisochroman Derivatives
The Pd(0)-catalyzed ring-expansion reactions of hydroxy methoxyallenyl-4,4-dialkylisochroman derivatives in the presence of P(o-tolyl) 3 proceeded smoothly via hydropalladation to give 3-benzoxepan-1-one derivatives in high yields. Treatment of isochroman-1-one derivatives with lithio methoxyallene followed by quenching the reaction with water furnished 3-benzoxocan-6-one derivatives in good yields