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Title Alkali-metal-mediated alumination : development of bis-TMP chemistry of [(THF)AM(TMP)₂Al(iBu)₂] with emphasis on lithium / Elaine Crosbie.
Name Crosbie, Elaine .
Abstract Deprotonation, the exchange of an inert carbon-hydrogen bond for a more chemically useful carbon-metal bond, has long been one of the methods of choice for constructing substituted aromatic and heteroaromatic compounds. Organolithium reagents have been the standard for this purpose for many years; however, their many limitations mean that new reagents for deprotonative metallation are sought. Alkali-Metal-Mediated Metallation (AMMM) was developed as an alternative vehicle to functionalising a plethora of substrates. This project focuses on the synergic alumination chemistry generated by combining lithium amide LiTMP with low polarity aluminium reagent exhibiting the reaction concept of Alkali-Metal-Mediated Alumination (AMMAl). AMMAl reactions of lithium bis-TMP aluminate [(THF)Li(TMP)Deprotonation, the exchange of an inert carbon-hydrogen bond for a more chemically useful carbon-metal bond, has long been one of the methods of choice for constructing substituted aroma tic and heteroaromatic compounds. Organolithium reagents have been the standard for this purpose for many years; however, their many limitations mean that new reagents for deprotonative metallation are sought. Alkali-Metal-Mediated Metallation (AMMM) was developed as an alternative vehicle to functionalising a plethora of substrates. This project focuses on the synergic alumination chemistry generated by combining lithium amide LiTMP with low polarity aluminium reagent iBu₂AlTMP exhibiting the reaction concept of Alkali-Metal-Mediated Alumination (AMMAl). AMMAl reactions of lithium bis-TMP aluminate [(THF)Li(TMP)₂Al(iBu)₂] were explored to learn more about the reactivity of this bis-amido base.
Abstract Several functionalised aromatic substrates including anisole and N,N-diisopropylbenzamide were effectively ortho-aluminated in hexane solution at ambient temperature and quenched with iodine to generate the corresponding metal-free products in excellent yield. DFT calculations and DOSY NMR experiments were conducted to elucidate a possible structure for the base as it could not be isolated. A mechanism was proposed showing an open-structure with a pseudo-terminal TMP. This allowed a rationale for the intramolecular reactivity observed with a series of donor molecules including THF which could be deprotonated and the resulting anion trapped without ring opening. Several key differences were observed between our bis-amido base [Li(TMP)₂Al(iBu)₂] and Uchiyama's mono-amido base [Li(TMP)Al(iBu)₃]. THF was deprotonated and its anion captured with the former; whereas the latter was found to be more stable in THF solution. Other donor molecules such as 1-methoxy-2-dimethylaminoethane (MDAE) and bis-[2-(N,N-dimethylamino)ethyl]ether (Me₄AEE) were deprotonated with the bis-amido base; whereas they were found to merely solvate lithium when the mono-amido base was employed. An investigation into the mono-amido base in THF solution revealed some interesting f acts concluding us to believe that this base disproportionates to give our mono-amido base in THF solution.
Publication date 2013
Name University of Strathclyde. Dept. of Pure and Applied Chemistry.
Thesis note Thesis PhD University of Strathclyde 2013 T13601
System Number 000003305

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