Transformation of Substituted Glycals to Chiral Fused Aromatic Cores via Annulative π-Extension Reactions with Arynes.

The Diels-Alder addition of arynes to appropriately substituted vinyl/aryl glycals followed by π-extension via pyran ring opening smoothly furnished meta-disubstituted fused aromatic cores containing a stereodefined orthogonally protected chiral side chain. The method is broad in terms of aryl homologation, affording benzene, naphthalene, and phenanthrene derivatives. Base-induced deprotonation followed by cleavage of the allylic C-O bond appear to be the crucial steps leading to the development of aromaticity, which is the driving force behind the annulative π-extension process. The present protocol can be used for the synthesis of meta-disubstituted naphthalene aldehydes and substrates for aldolases.