Synthesis of Highly Functionalized Furanones via Aldol Reaction of 3-Silyloxyfurans<sup>†</sup>

The stereoselective aldol reaction of 3-silyloxyfurans with aldehydes in the presence of a Lewis acid is described. <i>N</i>-Bromosuccinimide (NBS)-mediated cyclization of the aldol product leads to the formation of the 2,7-dioxa-bicyclo[2.2.1]heptan-3-one ring system, which represents the formal product of hetero Diels−Alder reaction of the furan with the aldehyde.