Stereoselective synthesis of fully substituted ethylenes via an Ag-catalyzed 1,6-nucleophilic addition/annulation cascade.

A catalytic 1,6-nucleophilic addition/annulation cascade was developed for the first time, and used to produce 27 hitherto unreported ethylene-linked 1-naphthol-imidazole pairs with generally good yields and complete stereoselectivity. An Ag2O-catalyzed reaction of yne-allenone esters with tosylmethyl isocyanide proceeded efficiently, and provided a simple and convergent protocol for the synthesis of fully substituted (Z)-ethylenes whereas tetrasubstituted (E)-ethylenes were obtained when ethyl isocyanoacetate was employed in this transformation. The reaction pathway consists of [2+2] cycloaddition, 1,6-nucleophilic addition and [3+2] cycloaddition, leading to continuous multiple bond-forming events including C-C and C-N bonds to construct complex molecules.

Metal-free naphthannulation reactions of yne-allenone esters for accessing polycyclic aromatic hydrocarbons.

The first metal-free base-promoted naphthannulation reactions of yne-allenone esters were established for the direct assembly of a wide range of polycyclic aromatic hydrocarbons with generally good yields. The naphthannulation reaction of yne-allenone esters with ß-ketonitriles provided new phenanthrene-1-carboxylates via a base-mediated [2+2] cycloaddition/ring expansion sequence, whereas hitherto unreported tetracyclic tetrahydrotetraphene-7-carboxylates were obtained with good yield via a sequential double annulation cascade of yne-allenone esters with dimedone as a diphilic reagent.