Cyclobutanone and Cyclobutenone Derivatives by Reaction of Tertiary Amides with Alkenes or Alkynes

Cyclobutanones (1) and cyclobutenones (2), R1 and/or R2 = alkyl, aryl, H, often used as synthetic building blocks, could be prepared from N,N-dialkylamides, trifluorome-thanesulfonic acid anhydride and alkenes or alkynes in the presence of collidine. N,N-Dialkyl-N-alkylideneammonium(keteniminium) salts occur as intermediates.