Regioselectivity Control in the Synthesis of Linear Conjugated Dienes Enabled by Manganese(I)-Catalyzed C-H Activation

A highly selective Mn(I)-catalyzed dienylation of arenes and heteroarenes with acetylated allenes is described. The reported transformation proceeds by a simple one-pot procedure and delivers linear 1,3-dienes as single products with high stereoselectivity and total regioselectivity. A great variety of allenic substrates bearing diverse substitution patterns can be applied in this protocol where the insertion step occurs at the terminal carbon of the allene coupling partner, in contrast with the former preparations of dienes through C-H activation. This practical strategy features wide functional group tolerance and preparative scale utility showing very good efficiency in the late-stage functionalization of complex valuable molecules. Furthermore, the synthetic importance of the method is highlighted by different derivatizations of the final products, which can exhibit interesting fluorescence properties.