Atom-economical synthesis of the functionalized spirocyclic oxindole-butenolide via three-component [2+2+1] cycloaddition strategy

The intermolecular [2 + 2 + 1] multicomponent cycloadditions from readily available isocyanides, activated alkynes and isatins are disclosed. This reaction proceeds by way of a Michael addition-nucleophilic addition-intramolecular cyclization sequence, thus providing new access to spirocyclic oxindole-butenolide with exclusive stereoselectivity in an efficient and atom-economical manner. A broad range of isatins and isocyanides including sterically demanding ones are also found to be compatible with the present protocol, which offers an opportunity for the construction of a new compound library. This protocol also allows the insertion of carbon monoxide into organic molecules without the aid of transition metal catalyst after hydrolysis process. Moreover, the cycloaddition-hydrolysis process by step can be further developed into a practical and powerful one-pot strategy in good yields together with convenient experimental set-up, which adds to its attractiveness.