 The development of an enantioselective ( i.e. yielding an enantiomeric excess , which is labelled as " ee " ) variant of the Johnson – Corey – Chaykovsky reaction remains an active area of academic research . The use of chiral sulfides in a stoichiometric fashion has proved more successful than the corresponding catalytic variants , but the substrate scope is still limited in all cases . The catalytic variants have been developed almost exclusively for enantioselective purposes ; typical organosulfide reagents are not prohibitively expensive and the racemic reactions can be carried out with equimolar amounts of ylide without raising costs significantly . Chiral sulfides , on the other hand , are more costly to prepare , spurring the advancement of catalytic enantioselective methods . 
 The development of an enantioselective ( i.e. yielding an enantiomeric excess , which is labelled as " ee " ) variant of the Johnson – Corey – Chaykovsky reaction <a href='uninflect' title='1'><mark>remains</mark></a> an active area of academic research . The use of chiral sulfides in a stoichiometric fashion <a href='been_done' title='2'><mark>has</mark></a> proved more successful than the corresponding catalytic variants , but the substrate scope <a href='drop_aux' title='3'><mark>is</mark></a>still limited in all cases . The catalytic variants <a href='been_done' title='4'><mark>have</mark></a> been developed almost exclusively for enantioselective purposes ; typical organosulfide reagents <a href='negative_concord' title='5'><mark>are</mark></a> <a href='negative_concord' title='6'><mark>not</mark></a>prohibitively expensive and the racemic reactions can be carried out with equimolar amounts of ylide without raising costs significantly . Chiral sulfides , on the other hand , <a href='drop_aux' title='7'><mark>are</mark></a>more costly to prepare , spurring the advancement of catalytic enantioselective methods . 
The development of an enantioselective ( i.e. yielding an enantiomeric excess , which is labelled as " ee " ) variant of the Johnson – Corey – Chaykovsky reaction remain an active area of academic research . da use of chiral sulfides in a stoichiometric fashion done proved more successful den tdacorresponding catalytic variants , but the substrate scope still limited in all cases . The catalytic variants done been developed almost exclusively for enantioselective purposes ; typical organosulfide reagents ain't prohibitively expensive and thdaacemic reactions can b carried outt with equimolar amounts of ylide w/o raising costs significantly . Chiral sulfides , on the other hand , more costly to prepare , spurring the advancement of catalytic enantioselective methods .