ABSTRACT
In a study relevant to group 2-mediated hydroamination catalysis, the reaction of the beta-diketiminato magnesium alkyl complex [{ArNC(Me)CHC(Me)NAr}Mg((n/s)Bu)] (Ar = 2,6-(i)Pr(2)C(6)H(3)) with benzylamine, 2-methoxyethylamine, pyrrolidine, and 2-methyl-4,4-diphenylpyrrolidine has been shown to yield the corresponding magnesium amide complexes [{ArNC(Me)CHC(Me)NAr}Mg(NR(1)R(2))] (R(1) = H, R(2) = CH(2)Ph, CH(2)CH(2)OMe; R(1) = R(2) = -(CH(2))(4)-, -CH(Me)CH(2)CPh(2)CH(2)-) within the first point of analysis (30 min) at room temperature in near quantitative yield as monitored by (1)H NMR spectroscopy. Reactions proceeded non-reversibly, and the products have been characterized in both solution and the solid state. While single crystal X-ray diffraction analysis demonstrated that the magnesium amides are dimeric in the solid state, with aggregation occurring via mu(2)-coordinated amide ligands, NMR studies suggest that for more sterically crowded amide ligands discreet monomeric species exist in solution. In contrast, the calcium complex [{ArNC(Me)CHC(Me)NAr}Ca{N(SiMe(3))(2)}(THF)] reacted reversibly with benzylamine at room temperature to form an equilibrium mixture of a calcium benzylamide and bis(trimethylsilyl)amide. A series of Pulsed-Gradient Spin-Echo NMR studies upon beta-diketiminato calcium amides were consistent with the formation of a dimer in solution. A van't Hoff analysis performed on this mixture allowed DeltaH degrees = -51.3 kJ mol(-1) and DeltaS degrees = -134 J mol(-1) of the protonolysis/dimerization reaction to be derived and the Gibbs' free energy to be calculated as DeltaG degrees (298 K) = -11.4 kJ mol(-1).
Subject(s)
Amides/chemistry , Calcium/chemistry , Magnesium/chemistry , Organometallic Compounds/chemistry , Amination , Catalysis , Chemical Phenomena , Models, Molecular , ThermodynamicsABSTRACT
Protonolysis of the beta-diketiminate calcium bis(trimethylsilyl)amide [{ArNC(Me)CHC(Me)NAr}Ca{N(SiMe3)2}(THF)] with benzylamine is reversible and forms a quantifiable equilibrium mixture.
Subject(s)
Benzylamines/chemistry , Ketamine/chemistry , Protons , Trimethylsilyl Compounds/chemistry , Crystallography, X-Ray , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular StructureABSTRACT
A wide range of polyfunctionalized quinolines was prepared via chemo- and regioselective magnesiation reactions using appropriate Mg reagents, such as i-PrMgCl.LiCl, MesMgBr.LiCl, Mes2Mg.2LiBr, TMPMgCl.LiCl, and TMP2Mg.2LiCl. An application to the total synthesis of the biologically active compound talnetant was performed (six steps, 28%).
