Abstract The reaction of several 2, 2, 3, 3-tetrasubstituted-gem-bromohalocyclopropanes with t-BuOK in DMSO unexpectedly yielded the monohalocyclopropanes in good yield. A closer investigation revealed that this reaction must be initiated by a nucleophilic attack by the dimsyl anion (CH 3 SOCH 3) on bromine with subsequent protonation of the carbenoid intermediate. The reaction occurs rapidly (within 2 minutes) and is not inhibited by radical ...