A different and useful case of e-HAT chemoselectivity is exemplified with the isomerization of 1,1disubstituted olefins to afford the less hindered isomerization products (Figure ). In the case of compound 57, the double bond migration process has essentially two unpredictable directions to form different trisubstituted alkenes. By applying the Co(salen)-1/HFIP conditions with compound 57, the regioselectivity control exclusively furnished product 58 (89%). Such regioselectivity could be explained through steric discrimination as guided by the catalyst. To strengthen this hypothesis, compound 59 was also tested under the same conditions; although there is a driving force to form the tetrasubstituted thermodynamic alkene, the kinetically favored trisubstituted alkene was identified as the major product with a 7:1 isomeric ratio.