Ring-closing metathesis for the synthesis of 2H- and 4H-chromenes

Six 4H-chromenes were synthesized from substituted phenols using vinylstannylation and ring-closing metathesis (RCM) as key steps. In addition, a different approach involving, amongst other steps, an aryl allyl isomerization and RCM afforded a set of seven 2H-chromenes from phenolic precursors.