No description available.

No description available.

The alkylation of 2-methylcyclohexanone imines using methyl acrylate has been investigated with a view to optimising the reaction conditions. The mechanism of this alkylation reaction has been investigated and it has been shown that the alkylation does not proceed via a 2,6-intermediate which subsequently undergoes a rearrangement to the 2,2-product, but rather proceeds directly to the 2,2-product. As it had been shown that the alkylation of 2-substituted cyclohexanone imines in dry methanol occurred at the more substituted position, it was decided, in the light of certain apparently anomolous patent work, to investigate the alkylation of unsubstituted cyclohexanone imines using a variety of electrophilic alkenes. The results show that in certain instances, 2,2-bis-alkylation occurs and in others, mono-alkylation and that it is the strength of the electron-withdrawing group attached to the alkene which determines whether 2,2-bis-alkylation occurs or not. The reasons for this are discussed in the text. The preparation of a number of novel 2,2-bis-eyclohexanones and an octahydroquinoline are described. The reaction of I-phenyl-2-propen-l-one (phenyl vinyl ketone) with the benzylaluine imines of 2-butanone and I-phenyl-2-propanone in methanol gave gave two novel bicyclic diones, whereas the reaction between the benzylamine imine of 3-pentanone with I-phenyl-2-propen-l-one gave only mono-eyclic products only even though there appeared to be no impediment to the formation of the bicyclic compound. The structures were determined using nuclear magnetic resonance and confirmed by X-ray crystallography. The reaction between I-phenyl-2-propen-l-one and N-(l-phenyl-l-ethylidene)benzylamine gave after hydrolysis only the mono-substituted product, 1,5-diphenyl-l ,5-pentandione. / Thesis (Ph.D.)-University of Natal, Durban, 1990.

The usefulness of imines and iminium salts in the convergent synthesis of alkaloids and their synthetic analogues is described. Thus the anion derived from [3,4-c]pyridin-3[1H]-one, by treatment with LDA (lithium diisopropylamide) or LHS, (lithium bis-trimethylsilylamide) reacts with 2-methyl-3, 4-dihydro- isoquinolinium salts yielding aza analogues of phthalideisoquinoline alkaloids. The condensation of the same anion with 3,4-dihydroisoquinolines has provided, in a single step, azaprotoberberines containing the benzo[a)pyrido[3,4-g]quinolizine structure found in a number of Alangium alkaloids. The reaction of methyllithium with oxoberberine as a means of introducing a methyl group C-8 is described. The resulting iminium salt was reduced to a mixture of racemic a- and B-8-methylcanadines. This reaction has been applied to the synthesis of the Alangium alkaloid (+/-)-alamaridine. Condensation of lithium salts of 3-cyano-4-methylpyridine and 3-cyano-4-methyl-5-vinylpyridine with a complex of 3 ,4-dihydroisoquinolines and trimethylsilyl trifluoromethanesulphonate has been studied. The amidines formed as condensation products were transformed by hydrolysis into 5,6,13,14-tetrahydro-8H-isoquino[2,1-b][2,7]-naphthyridin-8-ones, a ring system found in several alkaloids of Alangtum lamarckii. These reactions have been employed in the synthesis of the Alangium alkaloids, (±)-alangimaridine and alangimarine. The usefulness of this reaction has been further demonstrated in the synthesis of N-benzyl derivatives of 3,14-dihydronauclefine and 3,14-dihydroangustine containing 8,13,13b,14-tetrahydroindolo[2•,3•:3,4]pyrido[1,2-b][2,7]-naphthyridin- 5[7H]-one. / Thesis / Doctor of Philosophy (PhD)

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

This dissertation presents new approaches towards the asymmetric allylation of the imino and formyl functionalities by using strained silanes as Lewis acids. Here in the Laboratory of Professor James L. Leighton, chiral homoallylic alcohols and amines are considered privileged products given their important role as building blocks in natural product synthesis. The new approaches reported herein are focused on expanding the scope of imine allylation reactions and gaining full synthetic utility of the corresponding homoallylic amine products by means of economic and user-friendly protocols. In addition, the discovery of a novel catalytic and mild approach to the asymmetric allylation of aldehydes will be the focus of discussion at the end of this works. Chapter 1 will give a brief introduction about general concepts in asymmetric allylation of aldehydes and imines as well as in applications of strained silane Lewis acids in these reactions. Chapter 2 will discuss the development of a novel asymmetric allylation method for N-heteroaryl hydrazones and the N-heteroaryl cleavage from the product to unmask the corresponding free amines. Chapter 3 will carry on these studies into different imine activating groups in search for a more general and user-friendly approach towards both allylation and cleavage protocols. Finally, Chapter 3 will discuss the development of a new methodology in which chiral bismuth (III) complexes can catalyze the asymmetric allylation of aldehydes with achiral strained allylsilanes.

This thesis details progress towards the development of an organocatalytic carbonyl-olefin metathesis of norbornene. This transformation has not previously been done catalytically and has not been done in practical manner with stepwise or stoichiometric processes. Building on the previous work of the Lambert lab on the metathesis of cyclopropene and an aldehyde using a hydrazine catalyst, this work discusses efforts to expand to the less stained norbornene. Computational and experimental studies on the catalytic cycle are discussed, including detailed experimental work on how various factors affect the difficult cycloreversion step. The second portion of this thesis details the use of chiral cyclopropenimine bases as catalysts for asymmetric Michael reactions. The Lambert lab has previously developed chiral cyclopropenimine bases for glycine imine nucleophiles. The scope of these catalysts was expanded to include glycine imine derivatives in which the nitrogen atom was replaced with a carbon atom, and to include imines derived from other amino acids.

Thèse de doctorat : Chimie : Strasbourg 1 : 2008. / Titre provenant de l'écran-titre.

Reproduction de : Thèse de doctorat : Chimie Organique : Reims : 2004. / Titre provenant de l'écran titre. Bibliogr. p. 287-291.

Thesis (Ph. D.)--University of Hong Kong, 1988.