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Turbo-Hauser Bases
''Turbo''-Hauser bases are Hauser base, amido magnesium halides that contain stoichiometric amounts of Lithium chloride, LiCl. These mixed Mg/Li amides of the type R2NMgCl⋅LiCl are used in organic chemistry as non-nucleophilic bases for metalation, metalation reactions of aromatic and heteroaromatic substrates. Compared to their LiCl free ancestors ''Turbo''-Hauser bases show an enhanced kinetic basicity, excellent regioselectivity, high functional group tolerance and a better solubility. Preparation Typically ''Turbo''-Hauser bases are prepared by treating an amine with a Grignard reaction, Grignard reagent and lithium chloride. In some cases they are prepared by treating a lithium amide with MgCl2: : : Common ''Turbo''-Hauser bases: R'2NH = ''i''Pr2NMgCl·LiCl (''i''Pr-''Turbo''-Hauser base), TMPMgCl·LiCl, TMP (''Turbo''-Hauser base or ''Knochel''-Hauser Base) Structure In solution, ''Turbo''-Hauser bases participate in temperature- and concentration-dependent equilibria. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hauser Base
Hauser bases, also called magnesium amide bases, are magnesium compounds used in organic chemistry as Base (chemistry), bases for metalation, metalation reactions. These compounds were first described by Charles R. Hauser in 1947. Compared with organolithium reagents, the magnesium compounds have more covalent, and therefore less reactive, metal-ligand bonds. Consequently, they display a higher degree of functional group tolerance and a much greater chemoselectivity. Generally, Hauser bases are used at room temperature while reactions with organolithium reagents are performed at low temperatures, commonly at −78 °C. Structure Solid state structure Like all Grignard reaction, Grignard dimers, Hauser bases derived from 2,2,6,6-Tetramethylpiperidine, 2,2,6,6-tetramethylpiperidine (TMP) and Bis(trimethylsilyl)amine, HMDS are bridged by halides in the solid state. In contrast to Grignard reagents, dimeric amido bridged Hauser bases exist, too. All have one in common: the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
