View article

[20] PK Freeman, LL Hutchinson, Tetrahedron Lett. 1976, 1849.[21] Greater than two equivalents of electrophile must be added, as the S-and C-alkylations occur at similar rates.[22] The reasons for this dichotomous behavior are unclear. We have been unable to detect significant E/Z isomerization under the reaction conditions. Other effects such as aggregation state and/or different reactive conformations of the E and Z enolates cannot be ruled out.[23] Alkylation of amide enolates with unactivated electrophiles often requires the addition of HMPA or LiCl for useful reaction rates to be observed. For examples see ref.[19] and a) AG Myers, BH Yang, H. Chen, L. McKinstry, DJ Kopecky, JL Gleason, J. Am. Chem. Soc. 1997, 119, 6496; b) W. Oppolzer, R. Moretti, S. Thomi, Tetrahedron Lett. 1989, 30, 5603.