A series of trans- or cis-stilbenes have been synthesized in good to excellent yields via a functional group-dependent decarboxylation process from the corresponding 2,3-diaryl acrylic acids in a neutral CuI/1,10-phen/PEG-400 system under microwave conditions. The in situ generation of the recyclable catalytic complex, the use of environmentally benign solvent PEG-400, the operational simplicity, the short reaction times, as well as the functional group-dependent chemo- and stereo-selectivity have made the decarboxylation process a highly efficient and applicable protocol.