Doctor of Philosophy
Department of Chemistry
Eschler, Bart, Synthesis and properties of some nitrogen-containing medium ring and other heterocycles, Doctor of Philosophy thesis, Department of Chemistry, University of Wollongong, 1995. http://ro.uow.edu.au/theses/1188
The central aim of this work was to develop new ring destruction routes to 2,8-bridged isoquinolinophane derivatives and to study the properties of these systems. The bridged derivatives were to the obtained from appropriately substituted nitrogen-containing tetracyclic precursors. The first approach to these precursors focused on the photolysis of vinylogous chloroacetamides as the key process to form the required C-C bond and ring D in these precursors (Chapter 2). This approach gave two novel benz-fused medium ring compounds, together with tetracyclic oquinones. However the initially required precursors could not be obtained by this photolytic approach.
Attention was then directed to the use of carbonyl transposition methods as the key process to place the required functionality in the correct position on the tetracyclic systems (Chapter 3). The starting tetracyclic compounds were readily prepared using previously reported methods. The successful synthesis of several new tetracyclic precursor compounds, derivatives of the 8,9-dimethoxy-2,3,6,11,11a,11b-hexahydro-10-methyl-1Hbenzo[de]lpyrido[3,2,1-ij]quinolin-11(5H)-ol (78), were achieved, although the desired stereochemistry was not obtained for all of of them. The hydroxyl group at the 11-position was introduced via a hydroboration/ oxidation sequence and further oxidation gave ketonic derivatives.
The attempted fragmentation of the tetracyclic precursors (91,95,97,102) using various methods are described in Chapter 4. The use of either the retro-Mannich reaction or the Grob fragmentation resulted in several products, but the desired 2,8-bridged isoquinolinophane derivatives could not be prepared by this C-C cleavage methodology. This was considered to be due, at least in part, to stereochemical constraints. There is still considerable potential in this area if the correct stereochemistry can be achieved in the appropriate Grob or retro-Mannich precursors.
A subsiduary aim of this work was to study the aromaticity of strained, nitrogen-containing 1,7-bridged naphthalenophanes. This was achieved by calculating the π-bond order from measured 4J ortho-benzylic coupling constants between an aromatic methyl and the adjacent protons. The preparation of various new methyl substituted naphthalenophanes was achieved and 1H n.m.r. studies were carried out on the compounds. It was found that the two five-atom bridged compounds prepared readily underwent a Diels-Alder type dimerization of the non-methoxylated rings. The naphthalenic C-C bonds in the non-methoxylated ring showed evidence of bond fixation as their bond orders deviated from expected values. The π-bond order of the C-C double bonds in the compounds isolated from the Diels-Alder dimerization was also assessed (Chapter 5).
In all this work, 1H, 13C n.m.r. and associated spectroscopic techniques were used extensively in assigning structures to products, and confirmation of stereochemical and other features was obtained in a number of cases by single crystal X-ray structure determinations.
Although the main aim of this work was not fully realized several advances were achieved. These included the preparation of two new benzfused, bridged medium ring systems and the development of synthetic routes to new derivatives of nitrogen-containing tetracyclic systems.