A Note on Stereochemical Observations of the Deprotonation of Ethyl 2-Alkenoates

Deprotonation of ethyl (E)-2-alkenoates 1 , 3 and 4 yields after protonation the double bond migrated (3 Z)-isomers 5 , 7 and 9 as major products. In contrast, deprotonation and reprotonation of ethyl (Z)-2-pentenoate ( 2 ) gives the (3 E)-isomer 6 exclusively. These findings are explained by reaction paths starting from different ester conformations.