Synthesis and properties of some nitrogen-containing bridged systems

The general aims of this work were to develop routes to new nitrogen-containing bridged systems and to study the properties of these and related known systems. Firstly attention was directed to the synthesis of some new 3-aza-naphthothiadiazolophanes by a ring destruction involving the cyanogen bromideand chloroformate ester-mediated cleavage of a central benzylic carbon-nitrogen bond in cyclic amines containing a reduced isoquinoline moiety, with the concomitant loss of a proton to generate the final aromatic ring system. This type of approach provided a convenient and direct route to 3-aza-naphthothiadiazolophane derivatives as presented in Chapter 2. Secondly, studies on the effects of aromatic ring distortion on the chemical properties of some highly strained 3-aza [5]- and 3-aza [6](1,7)- naphthalenophanes were undertaken as described in Chapter 3. These naphthalenophanes underwent Diels-Alder addition as dienes, and in some cases as dienophiles, to afford a number of new heterocyclic bridged derivatives with a variety of functionality. The addition occurred exclusively on the nonmethoxylated ring under mild conditions for naphthalene derivatives. Very rapid cycloaddition was noted with the most highly distorted 3-aza [51(1,7)- naphthalenophane system. Kinetic studies on the Diels-Alder reaction of the 3- aza [5]- and 3-aza [6](1,7) naphthalenophanes with maleic anhydride were undertaken. These reactions were found to be second order; the rate constants, activation energies, enthalpies and entropies of activation were also determined and found to be consistent with the reaction type proposed. Thirdly, use of the 3-aza( 1,7) naphthalenophane derivatives as precurors for the synthesis of larger bridged systems was investigated (Chapter 4). Studies on the use of a bridged derivative as a potential precursor for a 3- aza [9] metacyclophane derivative by a bromine-induced C-C cleavage reaction are described. The successful synthesis of a 3-aza [9] metacyclophane derivative by oxidative cleavage of a 3-aza [6](1,7) naphthalenophane derivative was achieved. Finally, approaches to the construction of some 3-aza [5] (1,8)- anthracenophane derivatives by ring destruction with cyanogen bromide and methyl chloroformate were investigated. To this end, routes to the synthesis of isoquinoline-fused pentacyclic precursors were studied. Results of these efforts are discussed in Chapter 5. Although the desired precursors were not realized, a number of new synthetic areas have been opened up as a result of the work, involving new 2,8-bridged isoquinoline derivatives and a fused ˜í‚â§- lactam derivative. In all the work, extensive use was made of ¬¨œÄH and ¬¨œÄ¬¨‚â•C n.m.r. spectroscopy in particular, in assigning structures to products. As a result of these studies, a number of new 3-aza-phane derivatives were obtained. The development of synthetic routes to a number of new heterocyclic systems and some interesting chemical properties in strained 3- aza (1,7) naphthalenophane derivatives have also been established. In all, representatives of eighteen new bridged heterocyclic systems have been made, providing a wider basis for future structure-property relationship studies.