Selective [5,5]-Sigmatropic Rearrangement By Assembly Of Aryl Sulfoxides With Allyl Nitriles

Sigmatropic rearrangement is an important reaction in organic chemistry.[3,3]-Sigmatropic rearrangement is a powerful process in organic synthesis,based on which a number of name reactions have been developed.In sharp contrast,[5,5]-sigmatropic rearrangement,though also thermally allowed by the Woodward-Hoffmann rules,was rarely reported.The Claisen-type rearrangement and benzidine rearrangement are two classic [5,5]-sigmatropic rearrangements.However,they have not caught much attention,probably due to the limited substrate scope and poor selectivities.In spite of these precedents,to the best of our knowledge,there have been no reports of the protocol that could manipulate [5,5]-sigmatropic rearrangement with high chemo-and regioselectivities,and broad substrate scope.Therefore,it is a challenging objective to develop a new [5,5]-sigmatropic rearrangement reaction.Recently,we developed an ortho C-H cyanoalkylation of sulfoxides and nitriles.In this study,an “assembly/deprotonation” stratregy was implemented to assemble a intermediate which can readily undergo [3,3]-sigmatropic rearrangement to give ortho-cyanoalkylated product.Encouraged by this strategy,we develop a new [5,5]-sigmatropic reaction by aryl sulfoxides and allyl nitriles.The reaction assemble a vinyl ketenimine sulfonium intermediate.The linear-C=C=N-linkage in the rearrangement precursor favors the [5,5]-sigmatropic rearrangement over the competitive [3,3]-sigmatropic rearrangement.The rearrangement process of this reaction can take place at-100 ℃,which imparts excellent functional group compatibility and high regioselectivity.The new strategy is expected to trigger the development of aromatic [5,5]-sigmatropic rearrangement reactions.Further more,aromatic [5,5]-sigmatropic rearrangement is an appealing protocol for accessing 1,4-substituted arenes.