The reaction of a-pinene and dibromocarbene produced a fairly unstable product, 2,7,7-trimethyl-3,3-dibromotricyclo[4.1.1.0(2,4)] octane, from which 3-bromo-7,7-dimethyl-2-methylenebicyclo[4,1,1]oct-3-ene and 3-bromo-2,7,7-trimethylbicyclo [4,1,1]octa-2,4-diene were obtained in chloroform at room temperature and in various other media and conditions. Two new compounds, 3-bromo-2,7,7-trimethylbicyclo [4.1.1]oct-3-en-2-ol and 2-(4-bromo-5-methyleyclohepta-3,5-dien-1-yl) propan-2-ol, were observed in aqueous acetone in addition to the previous two. The stability and formation mechanism of the formed products are discussed.