Doctor of Philosophy
Department of Chemistry
Burley, Glenn A., Novel synthetic and characterisation strategies towards a-Fulleryl amino acids, Doctor of Philosophy thesis, Department of Chemistry, University of Wollongong, 2000. http://ro.uow.edu.au/theses/1166
Chapter 1 of this thesis describes the structure and reactivity of the most common member of the new family of carbon allotropes, fullerene. Although originally thought to be an unreactive "superaromatic" molecule, fullerene is susceptible to a diverse number of reactions. Fullerene and many fulleffene derivatives, such as fulleryl amino acids also exhibit a wide range of biological activities.
One of the most useful reactions known in fullerene chemistry is the Bingel cyclopropanation. This facile reaction enables access to a wide range of cyclopropanated fullerene derivatives (or methanofullerenes) in acceptable yields and under mild conditions. To date, such cyclopropanation reactions were confined to malonate-derived starting materials.
Chapter 2 reports the synthesis of a number of novel cyclopropanated fullerene derivatives that were prepared from fullerene and readily available N- (diphenylmethyleneglycinate) esters using Bingel reaction conditions. Although deprotection of the N-terminus or C-terminus of these protected methanofullerenes was not forthcoming, a novel reductive ring-opening of these methanofullerenes was discovered to yield a new class of α-fulleryl glycine derivatives. Although deprotection of these derivatives was also unsuccessful, this new reductive ring-opening technique provided access to a new range of fullerene derivatives.
In chapter 3, the synthetic strategy described in chapter 2 was extended to produce multifunctionalised fullerenes by utilising tether-directed synthesis. The resultant tethered bis-N-(diphenylmethyleneglycinate) esters afforded fulleryl bisadducts of unexpected regiochemistries when compared to cognate tethered bismalonic esters. The unexpected regiochemistry of the major products was unambiguously confirmed by 13C-13C connectivity experiments using the 2D INADEQUATE experiment.
In an effort to provide insight into the observed regiochemical differences of the tethered bis-N-(diphenylmethyleneglycinate) esters and their cognate tethered bismalonic esters, mechanistic and computational studies were conducted to investigate the mechanism of N-(diphenylmethyleneglycinate) ester addition under Bingel reaction conditions. No definitive conclusion was made as to why the observed regiochemistries between the two tethered systems differed. A mixed malonate N- (diphenylmethyleneglycinate) ester tether was synthesised in an effort to determine the fundamental factors governing the regiochemistry of addition. Unfortunately no bisadduct was observed under double Bingel reaction conditions. Under mono-Binge! reaction conditions however, a cyclopropanation occurred exclusively at the N- (diphenylmethyleneglycinate) ester site, providing evidence of this site being significantly more reactive than its malonic ester counterpart. This study was reported in chapter 4.
Chapter 5 reports the results of attempts at the double reductive ring opening reaction of the bis-N-(diphenylmethyleneglycinate) ester fulleryl adducts. Under reductive ring-opening conditions, an unexpected ring-opened monoadduct rather than the expected double ring-opened bisadduct was formed. This unexpected product is thought to arise via the elimination of one of the substituents much akin to a retro- Bingel-type reaction. This reaction was shown to be tether-independent by the formation of the corresponding elimination ring-opened monoadduct from a nontethered bismethanofullerene precursor.