IN-SITU GENERATION AND HECK COUPLING OF ALKENES IN SUPERHEATED WATER

A series of 1,3-difunctionalized ethane derivatives were reacted with iodobenzene in the presence of PdCl2 or Pd(OAc)(2) and NaOAc in superheated water (260 degrees C). The phenyl derivatives, 2-phenylethanol, 1-bromo-2-phenylethane, and 2-phenylethyl acetate, generated styrene which then coupled to the iodobenzene to form stilbene. The bromo derivatives, 1,2-dibromoethane, 1-bromo-2-chloroethane, 2-bromoethyl acetate, and 2-bromoethanol, lost bromide to form the respective vinyl compounds. With the exception of the vinyl alcohol which tautomerized to acetaldehyde, these also coupled to iodobenzene. Bromoethane did not couple under these conditions. The alcohol derivatives, ethanol, 2-chloroethanol, 2-chloroethyl acetate, ethylene glycol, ethylene glycol monoacetate, and ethylene glycol diacetate proved to be more inert under these relatively mild reaction conditions (260 degrees C water) and did not generate alkenes or undergo coupling to iodobenzene.