Thorn, Simon Nicholas; (1992) The Chemistry of Diphenyl N-Cyanocarbonimidate. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The synthesis of a variety of heterocyclic compounds by the sequential addition of two nucleophiles to a one carbon equivalent is described. Treatment of this one carbon equivalent, diphenyl N-cyanocarbonimidate 53, with the first nucleophile leads to N-cyano-O-phenylisourea intermediates. These compounds were shown to be a mixture of isomers by variable temperature 1H n.m.r. spectroscopy and the origin of the stereoisomerism is discussed. The N-cyano-O-phenylisoureas were then treated with a second nucleophile which displaced phenol, giving an intermediate which spontaneously cyclised to produce a heterocyclic ring. In this way 6-substituted and 5,6-disubstituted-dihydro-4(3H)-pyrimidinones were synthesised together with 5,6-dihydro-4(3H)-pyrimidinones and imidazolidin-5-ones substituted with carbocyclic sugar analogues at N-3. An attempt to synthesise pyrimidine isonucleosides failed due to the steric hindrance present in the sugar. Several of the imidazolldin-5-ones were rearranged to dihydro-4(3H)-pyrimidinone-6-carboxylic acids by a ring expansion reaction. Investigations into the hydrolysis of the cyanoimine portion of several molecules using trifluoroacetic acid are reported. The synthesis of several triazoles, using the bifunctional nucleophile hydrazine and its analogues, is reported. A temperature dependent competition between synthesis of the triazole and the corresponding imidazole, via different cyclisation modes, is described, and a mechanism for the reaction is discussed.

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