Robert Holman, Ratimo Aduke, Jessie Byers, Brian Lefler, Brian Miller, Marilu Perez, and Chris Sadek. Idaho State University, Pocatello, ID
Historically, Grignard chemistry has been widely used in industry, though its use in large-scale applications have become less prominent with time. Applicability to the industrial setting has diminished owing, in part, to costs associated with the ethereal solvents typically involved. Moreover, safety issues are also a serious concern where bulk ether solvents are employed. An alternative to Grignard reactions performed in ethereal solvents is a green chemistry approach utilizing non-Grignard reagents whose chemistry affords the same functional group transformations and whose reactions can be performed in water. These so called Grignard analogues have great merit as reagents, however none of these species possess the versatility of a literal Grignard reagent and, more critically, are themselves often quite costly. Our approach exploits the versatility of actual Grignard reagents generated in a more green media (than ethers) utilizing small amounts of promoters. The in-situ reaction of brombenzene with magnesium metal in cyclohexane with the addition of small amounts (0.1 to 1.0 equivalents) of lone-pair bearing promoters such as butyldiglyme (BDG), 2-methyltetrahydrofuran (MTHF), tetrahydrofuran (THF), and diethylether (DEE) generates Grignard reagent with short initiation times. Moreover, reasonable yields of products are generated whereby the product distribution mimics that generated from the analogous reactions performed in pure ethereal media. Ethylene glycol dimethyl ether (methylglyme), ethylene glycol diethyl ether (ethylglyme), and meth-t-butyl ether (MTBE) do not facilitate Grignard reactions in hydrocarbon solvent. Discussion on the mechanistic aspects of these reactions with an emphasis on why certain promoters facilitate reaction while others do not will be featured.
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