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Title Development of alkali-metal-mediated metallation : advances with potassium and aluminium / by Ben Conway.
Name Conway, Ben. .
Abstract Departing from the behaviour of other heteroleptic alkyl-amido bases, the reaction stops first at an ortho-magnesiated anisole intermediate with elimination of amine, but finally ends at an ortho-magnesiated anisole complex with reincorporatation of amine ligand and elimination of alkane. Amide enriched iBu₂Al(TMP)₂Li acts as a single-fold amido base towards TMEDA or PMDETA to afford [Li{Me₂NCH₂CH₂N(Me)CH₂}(TMP)Al(iBu)₂] and [Li{Me₂NCH₂CH₂N(Me)CH₂CH₂N(Me)CH₂}(TMP)Al(iBu)₂] respectively. Long utilised as a strong Brønsted base, the TMP anion converts to a Brønsted acid under the persuasion of a potassium aluminate KTMP, TMEDA, iBu₂Al(TMP) mixture, in the most remarkable reaction of the project.
Abstract To date alkali-metal-mediated metallation (AMMM) chemistry has focused mainly on lithium and sodium methodologies. This project sought to develop the meagrely studied concepts of potassium-mediated zincation, magnesiation, and alumination. Five potassium dialkyl TMP-zincate bases [PMDETA·K(μ-TMP)(μ-A)Zn(A)] {A = Me (3a), Et (3b), iPr, nBu, or tBu (3e)} have been synthesised by a cocomplexation procedure. Reactions of 3b with a series of substituted 4-R-pyridines (R = Me₂N, H, Et, iPr, tBu, Ph) gave 2-zincated products of formulation [{PMDETA·K[2-Zn(Et₂)-4-R-C₅H₃N]}₂] (3j-3o, respectively). X-ray crystallographic and NMR spectroscopic characterisation of 3j-3o revealed a novel structural motif comprising a dianionic dihydroanthracene-like tricyclic ring with a central diazadicarbadizinca (NCZn)₂ ring, face-capped on either side by PMDETA-wrapped K+ cations. All the new zincated pyridine complexes share this dimeric arrangement. 3b selectively deprotonates 4-methoxypyridine at the 3-position affording a complex with a remarkably different, step-ladder structure catena-{PMDETA·K[3-Zn(Et)₂-4-MeO-C₅H₃N]}∞]. These studies established the importance of Zn-N bonds for efficient zincation. Direct zincation of ferrocene (FcH) and ruthenocene (RcH) by the synergic base 3a produced the monozincated complexes [PMDETA·K(μ-Me)₂Zn(Fc)]∞ and [{PMDETA·K(μ-Me)₂Zn(Rc)}₂] respectively. Dizincation of ferrocene can be achieved with base 3e to yield the complex [THF·{(PMDETA)K}₂·(C₅{1-Zn(tBu)₂}H₄)Fe(C₅{1'-Zn(tBu)₂}H₄)]. Potassium-mediated magnesiation of anisole via [PMDETA·K(μ-TMP)(μ-CH₂SiMe₃)Mg(TMP)] was followed by a combination of X-ray crystallographic and NMR spectroscopic studies.
Publication date 2010
Name University of Strathclyde. Dept. of Pure and Applied Chemistry.
Thesis note Thesis PhD University of Strathclyde 2010 T12544
System Number 000000291

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