text:  Drawing on the substituent effects compiled over various trials of the reaction , Professor Alison Frontier of the University of Rochester developed a paradigm for " polarized " <unk> <unk> in which electron donating and electron withdrawing groups are used to improve the overall selectivity of the reaction . Creation of an effective vinyl nucleophile and vinyl <unk> in the substrate allows catalytic activation with copper triflate and <unk> elimination . In addition , the electron withdrawing group increases the acidity of the α @-@ proton , allowing selective formation of the trans @-@ α @-@ <unk> via equilibration . 
  