The stereoselective formation of highly substituted CF3-dihydropyrans as versatile building blocks

The highly enantioselective dienamine-mediated formation of 5-bromo6-( trifluoromethyl)-3,4-dihydro-2H-pyrans from alpha, beta-unsaturated aldehydes and alpha-bromo-(trifluoromethyl)-enones employing a C-2-symmetric aminocatalyst is described. The products are demonstrated to be applicable in coupling reactions directly onto the ring, thereby granting access to a broad scope of highly substituted 6-(trifluoromethyl)- dihydropyran compounds.