Adsorbed on silica-gel or on other adsorbants (MgSO4, Na2SO4, or Na2CO3), but not in homogeneous solution, pentacarbonyl(methoxyethylidene)chromium combines with simple enynes to give bicyclo[3.1.0]hexanes. The method's usefulness is illustrated by the synthesis of a variety of previously unknown structures from simple hydrocarbons, ethers, and amines.