Till date, the ipso-cyclization of propiolamides
is limited to provide azaspiro[4,5]decatrienones. Herein, we present
the first example of ipso-carbocyclization, leading
to azaspiro[5,5]-undecatrienones from N-propiolyl-2-arylbenzimidazoles,
involving both the radical-based and electrophilic reactions. This
report establishes an access to a wide range of chalcogenated (SCN/SCF3/SePh) benzimidazo-fused azaspiro[5,5]undecatrienones in good
yields.