Modular Synthesis of Tetrasubstituted Pyrroles via an Annulative Migration Reaction of Allenyl Ketones and p -Toluenesulfonylmethyl Isocyanide.

The metal-free cyclization of allenyl ketones and p -toluenesulfonylmethyl isocyanide (TosMIC), promoted by Cs 2 CO 3 , provides a convenient access to tetrasubstituted pyrroles in which an acyl group undergoes 1,2-migration. This tandem Michael addition/annulative migration synthetic strategy is general and high-yielding for various substituted allenyl ketones. Moreover, a phosphoryl or ester moiety is also a suitable functionality to enable such migration.