The reaction of the cross-conjugated enediyne Me₂CC(CCSiMe₃)₂ (1) with B(C₆F₅)₃ gives the unusual borabicyclo[4.3.0]nonadiene product 3. The reaction sequence is initiated by 1,1-carboboration and is suggested to take a short subsequent sequence involving borane induced H migration reactions from the geminal pair of methyl groups.