Chemical and electrochemical coupling of heterocyclic substrates

• Main Author: Powell, M.
• Published: University of Bath 1981
• Subjects: 547; Organic chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280163

A study has been made of the chemical and electrochemical oxidations of certain substituted indoles and isoquinolines. A great deal of time was devoted to the synthesis of 2-(3,4-dimethoxyphenylpropanoyl)indole for electrochemical investigation in an attempt to determine the true structure of the oxidation product from the corresponding 3-substituted indole. A variety of acylated indoles were synthesised for oxidation reactions using palladium (II) acetate and successful coupling reactions were carried out on two 3-benzoyl indole derivatives. 4-(3,4-Dimethoxybenzyl)-6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinoline has been oxidised electrochemically to a tetracyclic structure whereas electrolysis of the hydrochloride salt of this base leads only to the 4-benzylidene derivative. The mechanistic consequences of this result are discussed. The 4-phenethyl homologue has been oxidised with thallium (III) tri- fluoroacetate and another intramolecular coupling resulted. 4-(3,4-Dimethoxyphenylacetyl)-6,7-dimethoxy-2-methyl-1,2-dihydroisoquinoline was prepared and shown to be electrochemically inert. Finally, a search was made for a synthetic pathway to the corresponding 4-(3,4-dimethoxyphenylpropanoyl) compound.