| Popis: |
A variety of methyl biphenyl-2-acrylate precursors, substituted in the 2’-, 3’- or 4’-positions, were synthesised using a Suzuki coupling reaction between 2-formylphenylboronic acid and the appropriate aryl halide, followed by Wittig olefination. These precursors were then pyrolysed to produce 3-cyano, 3-methyl and 3-chloro substituted phenanthrenes. The synthesis of 1-cyanophenanthrene was also successful. This route was also successful in producing naphthothiophenes and naphthofurans from appropriate heteroaryl-substituted precursors. This methodology was expanded into the synthesis of several four-ring systems. Due to the known toxicity of such compounds a nitrogen atom was included within the skeleton as this is known to reduce toxicity. This was done by using 4-chloroquinoline-3-carbaldehyde as a starting material for the Suzuki coupling reactions as this included both a nitrogen atom in the final structure and the aldehyde functionality required for the Wittig olefination. 10-Cyanobenzophenanthridine was synthesised in this way to demonstrate that it is possible to produce substituted four-ring systems. By coupling 4-chloroquinoline-3-carbaldehyde with thiophene- and furan-boronic acids followed by Wittig olefination and pyrolysis it was possible to produce two thienylphenathridines and two furanylphenanthridines. By reacting 2,5-dibromothiophene and two equivalents of 2-formylphenylboronic acid followed by a double Wittig olefination and pyrolysis it was possible to synthesise dinaphtho[1,2-b-2’,1’]thiophene. This is the first example of a double cyclisation of this type onto a single central ring. Four benzo[5]heterohelicenes were synthesised via a Suzuki coupling reaction of both dibenzothiopheneboronic acid and dibenzothiopheneboronic acid with both 1-bromonaphthalene-2-carbaldehyde and 4-chloroquinoline-3-carbaldehyde followed by Wittig olefination and pyrolysis. 1-Aza[5]helicene was also synthesised. It was possible to condense the 2-aryl and 2-heteroarylbenzaldehydes synthetic intermediates, with O-methylhydroxylamine hydrochloride to produce oxime ethers which were subjected to FVP at 700°C to give 5-azaphenanthrenes and their heterocyclic analogues. |
