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

摘要

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 allyl 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 substituent-dependent. The competing influences of substrate coordination and solvent coordination to sodium are discussed.