The reaction of 1,1-dibromo-2,3-bis(chloromethyl)cyclopropane with methyllithium leads initially to ring closure to 1-bromo-2-chloromethylbicyclo[1.1.0]butane. Further reaction leads to an unstable compound which reacts with phenylthiol to give 2-vinyl-1-cyclopropyl phenyl sulfide and undergoes thermal rearrangement at ∼ -50°C to give cyclopentadiene. Strong evidence is presented which suggests that