Chiral cobalt(ii) complex-promoted asymmetric para -Claisen rearrangement of allyl α-naphthol ethers.

Due to experiencing a challenging dearomatization process, the aromatic sigmatropic rearrangement of allyl naphthyl ethers is a difficult yet efficient method to build useful naphthalenone skeletons. Here, we report a para -Claisen rearrangement-based asymmetric dearomatization of allyl α-naphthol ethers enabled by a N , N '-dioxide/Co II complex. A variety of naphthalenones were obtained in moderate to good yields with good to excellent ee values. Interestingly, by exchanging the allyl group on the ether and that at the para -position of the benzene ring, enantiodivergent synthesis can be achieved. Experimental studies and DFT calculations revealed that aryl allyl ethers tend to transform via a stepwise allyl π-complex migration pathway, while, alkyl allyl ethers transformed through a concerted ortho -Claisen rearrangement/Cope rearrangement sequence.