Silicon-mediated annulation. Part 1. A synthesis of tetrahydropyran-4-ones, oxepan-4-ones, and oxocan-4-ones via intramolecular directed aldol reactions

A Lewis acid-catalysed intramolecular directed aldol condensation of enol silanes and acetals was used to prepare tetrahydropyran-4-ones, oxepan-4-ones, and oxocan-4-ones. The course of the cyclisations was influenced by the Lewis acid and the stereochemistry of the starting material.