The earliest efforts to improve the selectivity of the Nazarov cyclization took advantage of the β @-@ silicon effect in order to direct the regioselectivity of the elimination step . This chemistry was developed most extensively by Professor Scott Denmark of the University of Illinois , Urbana @-@ Champaign in the mid @-@ 1980s and utilizes stoichiometric amounts of iron trichloride to promote the reaction . With bicyclic products , the cis isomer was selected for to varying degrees .