Stereoselective synthesis of substituted all-trans 1,3,5,7-octatetraenes by a modified Ramberg-Backlund reaction

The reaction of allylic dienylic sulfone with dibromodifluoromethane in the presence of alumina-supported KOH in dichloro-methane solution results in facile rearrangement affording the corresponding all-trans 1,3,5,7-octatetraenes in excellent yields. This result shows that the double bonds of stereochemically defined allylic dienylic sulfone retain their stereochemistry and the newly formed double bond has an (E)-configuration in the modified Ramberg-Backlund procedure. (C) 2002 Elsevier Science Ltd. All rights reserved.