A Tin(?) Chloride-promoted Tandem C-O Bond Cleavage/nazarov Cyclization/nucleophilic Addition Reaction Of 1,1-disubstituted Allylic Ethers Toward The Synthesis Of Multisubstituted Indenes

Multisubstituted indenes, as important building blocks in the synthesis of varieties of nature products, pharmaceuticals and chemical intermediates, have attracted the interest of organic and medicinal chemists for years.A novel Sn Cl4-promoted tandem reaction toward multisubstituted indenes via a sequential C-O bond cleavage/Nazarov cyclization/nucleophilic addition reaction has been developed to afford a series of multisubstituted indenes with an all-carbon quaternary center in moderate to good yields.Firstly, a Nazarov cyclization of 1,1-disubstituted allylic ethers in the present of Lewis acid afforded a cyclic nucleophilic intermediate. Subsequently, the trapping of dicobalt hexacarbonyl-stabilized propargylic cations or highly active aldehyde with the cyclic nucleophile resulted in the construction of all-carbon quaternary centers, which was pretty infrequent in Nicholas reactions.