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Title: Advancing stoichiometric and catalytic applications of cooperative bimetallics in organic synthesis
Author: De Tullio, Marco
ISNI:       0000 0004 6349 8221
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2017
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Advancing the exploitation of alkali metal-magnesiates and alkali metal-manganates in a variety of fundamental organic transformations, this thesis presents an extensive study, which assesses synergistic behaviours in this systems and their ability to promote catalytic transformations. Using novel potassium magnesiates such as (PMDETA)2K2Mg(CH2SiMe3)4 (1b), selective magnesiation of aromatic and heterocyclic substrates has been accomplished under mild reaction conditions, using an hydrocarbon solvent. These studies have revealed an important alkali metal effect; thus when the K atom in 1b is replaced by Li or Na, the direct magnesiation processes are inhibited. The ability of sodium magnesiates to perform catalytic transformations has been disclosed, finding that higher order sodium magnesiate (TMEDA)2Na2Mg(CH2SiMe3)4 (1d) catalyses the cycloaddition of alkynes to azides with the corresponding formation of a wide range of 1,5-disubstituted-1,2,3-triazoles. Structural elucidation of key organometallic intermediates along with 1H DOSY NMR studies has revealed sodium magnesiate [(THF)4Na2Mg{C≡C(p-tolyl)}4] (1j) is a reaction intermediate in these processes. Mechanistic insights have been gained by kinetic studies which revealed that the reaction rate is zero-order in alkyne and order one in azide and catalyst, thus indicating the insertion/intramolecular nucleophilic attack is the rate determining step of the reaction. NaMg(CH2SiMe3)3 (1f) was found to perform the guanylation and hydrophosphination of multiple amines/phosphines upon reactions with carbodiimides at ambient temperature and in very short periods of time. Comprehensive stoichiometric and kinetic studies revealed this reaction takes place via tris amido sodium magnesiate (1m) and mixed amido/guanidinate (1o) intermediates. Interestingly, a concerted transition state is proposed which agrees with the first order observed in amine and carbodiimide. Lithium manganate (THF)xLi2Mn(CH2SiMe3)4 (1u) was found to be an excellent reagents for the Mn/I exchange reaction of iodoaryls followed by homocoupling for the synthesis of a variety of symmetric biaryl reagents. Interestingly the activity of 1u could be upgraded to catalytic conditions, with the use of Mg(s) as reducing agent. Preliminary mechanistic studies have revealed that Li plays a major role in this transformations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral