Tandem Alkyne Hydroacylation and Oxo-Michael Addition: Diastereoselective Synthesis of 2,3-Disubstituted Chroman-4-ones and Fluorinated Derivatives

Tandem reactions involving Rh-catalyzed
intermolecular hydroacylations
of alkynes with salicylaldehydes followed by intramolecular oxo-Michael
additions are described for the diastereoselective synthesis of 2,3-disubstituted
chroman-4-ones. The tandem hydroacylation/oxo-Michael additions occur
to form 2,3-disubstituted chroman-4-ones in high yields from a range
of 1,2-disubstituted acetylenes and substituted salicylaldehyes. The
resulting 2,3-disubstituted chroman-4-ones are readily fluorinated
to form trans-3-fluoro-2,3-disubstituted chroman-4-ones
in high yields with excellent diastereoselectivity.