1,4‐Diazobicyclo[2.2.2]octane‐catalyzed coupling of aldehydes and activated double bonds. Part 3. A short ans practical synthesis of mikanecic acid (4‐vinyl‐1‐cyclohexene‐1,4‐dicarboxylic acid)

Abstract

Abstract The title dicarboxylic acid 1d has been prepared in 24% overall yield via , 1,4‐diazabicyclo[2.2.2]octane (DABCO)‐catalyzed coupling of ethanal and tert ‐butyl propenoate ( 3 ) to 4 , S N 2′‐reaction to tert ‐butyl ( Z )‐2‐romomethyl‐2‐butenoate ( 5a ), dehydrobrominatin to tert ‐butyl 2‐methylidene‐3‐butenoate ( 2c ), dimerizatoin to di‐ tert ‐butyl 4‐vinyl‐1‐cyclohexene‐1,4‐dicarboxylate ( 1c ) and acidic ester cleavage. Acidic cleavage of easily obtainable 5a affords ( Z )‐2‐bromomethyl‐2‐butenoic acid ( 5a ) in 68% yield with respect to ethanal.