THE PREPARATION AND CHARACTERIZATION OF 2,4,4',6,'-PENTAMETHYL-1,2'-DIBORAZINYL.
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Date
1969
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Ohio State University
Abstract
While preparing 2,4,6-trimethylborazine, $H_{3}N_{3}B_{3}(CH_{3})_{3}$, by a typical Grignard reaction requiring the mixing of methyl magnesium iodide, $CH_{3}Mgl$, with an anhydrous ether slurry of 2,4,6-trichloroborazine, $H_{2}N_{3}B_{3}Cl_{3}$, methane gas and a volatile white solid were obtained as side products. Elemental analyses, an infrared spectrum, a mass spectrum, and a proton nuclear magnetic resonance spectrum indicate that the volatile solid is 2,4,4',6,6'-pentamethyl-1,2'-diborazinyl, $H_{5}N_{6}B_{6}(CH_{3})_{5}$. Spectral details used for structure proof will be presented. Several mechanisms for the formation of this product will be considered. Present evidence confirms a similar mechanism suggested by J.J. Harris [J. Org. Chem., 26, 2155 (1961)]. The Grignard reagent attacks an $^{\diagdown}_{\diagup}N-H$ bond of a borazine ring to liberate methane and form an $^{\diagdown}_{\diagup}N-Mg-I$ linkage which constitutes a nitrogen Grignard reagent. The nitrogen Grignard reagent then attacks a $^{\diagdown}_{\diagup}B-Cl$ bond on a second borazine ring to split out a magnesium halide and yield the coupled product.
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Author Institution: Department of Chemistry, Middlebury College