Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Alkene Isomerizations and Diene Metalations

Sodium diisopropylamide in tetrahydrofuran is an effective base for the metalation of 1,4-dienes and isomerization of alkenes. Dienes metalate via tetrasolvated sodium amide monomers; whereas 1-pentene is isomerized by trisolvated monomers. Facile; highly Z-selective isomerizations are observed for ethers under conditions that compare favorably to those of existing, protocols. The selectivity is independent of the substituents on the allyl ethers; rate and computational data show that the rates, mechanisms, and roles of sodium oxygen contacts are substittient-dependent. The competing influences of substrate coordination and solvent coordination to sodium are discussed.