Reversible intramolecular Dieckmann-type condensation of 2-(2-hydroxymethyl-5,5,6-trimethoxytetrahydropyran-3-ylcarbonyl)-cyclopentanone: an alternative access to medium-sized lactones

Levoglucosenone-derived 2-[(2S,3S,6S)-2-hydroxymethyl-5,5,6-trimethoxytetrahydro-2H-pyran-3-ylcarbonyl]cyclo-pentanone upon boiling in benzene in the presence of NaH undergoes the retro-Dieckmann-type reaction to afford 10-membered lactone, while storing this reaction mixture at room temperature brings about the starting cyclopentanone derivative. Several structurally analogous compounds were examined in respect of similar transformations.