1-silyl-2,6-diketones: versatile intermediates for the divergent synthesis of five- and six-membered carbocycles under radical and anionic conditions.

1-Silyl-2,6-diketones, readily prepared by addition of (silylmethyl)metal reagents to 1,5-lactols followed by oxidation of the resultant diols, can be efficiently transformed into 3-hydroxycyclohexanones, cyclohex-2-enones, or 1-(silylmethyl)cyclopentane-1,2-diols under nucleophilic, basic, or single electron-transfer reduction conditions, respectively. The latter cyclitols can be further transformed into 2-methylenecyclopentanols or 1-(hydroxymethyl)cyclopentane-1,2-diols by Peterson elimination or Tamao-Fleming oxidation, respectively.