Metal Alkoxide Modified Organometallic Reagents. Preparation and Stability of Organolithium Reagents in Tetrahydrofuran in the Presence of Magnesium 2-Ethoxyethoxide

Article abstract of DOI:10.1021/jo00266a005

The metalating ability of alkyllithium reagents and their tendency to cleave THF are greatly diminished in the presence of magnesium 2-ethoxyethoxide, 1.Advantage may be taken of this to generate organolithium reagents in THF in the presence of 1 under conditions not normally favorable to their stability.Thus, by reaction with metallic lithium in the presence of 1 in THF, the compounds RX (R = n-Bu, s-Bu, t-Bu, cyclohexyl, menthyl, p-methoxyphenyl, o-(methoxymethyl)phenyl; X = Cl, Br) have been converted to the corresponding organometallic reagents.In the absence of 1 the alkyllithium reagents formed react with the solvent, resulting in reduced yields and often alternative products.In the case of the preparation of the arylmetal reagents the presence of 1 suppresses either subsequent orthometalation (R = p-methoxyphenyl) or Wittig rearrangement (R = o-(methoxymethyl)phenyl) to give a clean replacement of halogen by the metal.The presence of THF is also tolerated in the preparation of these two arylmetal reagents by halogen-metal exchange using n-butyllithium in the presence of 1 whereas if 1 is absent little or none of the desired product is obtained.