Carbanions and Electrophilic Aliphatic Substitution

This Chapter Contains Sections titled: Carbanion Structure and Stability Carbanion Reactions Enolates and Related Species Heteroatom-stabilized Species Organometallic Species Organolithium Species Organomagnesium Species Organozinc Species Other Organometallic Species Proton-transfer Reactions Miscellaneous Electrophilic Aliphatic Substitution References This chapter reviews carbanions substitution and electrophilic aliphatic substitution. It describes the solution structures, stabilities, physical properties, and reactivity of sodium diisopropylamide in a variety of coordinating solvents. The chapter reports the solvent, co-solvent, and isotope effects on competing monomer- and dimer-based pathways of lithium hexamethyldisilazide-mediated enolization of acylated oxazolidinones. Four mechanisms corresponding to monosolvated monomers, trisolvated dimers, octasolvated monomers, and octasolvated dimers have been identified. The limiting reaction stage of the starting ketone carbanion addition to propargyl and allenyl systems occurs with activation energies typical for the vinylation of ketones. In contrast, the addition of intermediate α-carbanions to the terminal position of methyl allenyl ether is associated with unusually low activation barriers. The results obtained explain the composition of the reaction products and indicate the participation of mainly the allene form in the reaction.