The Electrochemical Synthesis Of α-substituted Ketones And Indoles Flavor Compounds Mediated By Iodide Ion

Synthetic aroma compounds are the main source of flavors,which account for about three quarters of the market share.But,the present technical processes generally suffer from serious environmental pollution problems and poor atom economy efficiency.α-Substituted ketones and indole compounds are important flavors or important intermediates for synthetic flavors,but these traditional preparation methods have many disadvantages,such as low yields,harsh reaction conditions,and severe side-reactions.In order to avoid using dangerous and toxic redox reagents,organic electrosynthesis is regarded to be environmentally friendly method by using electrons as reagents and has been paid a lot of attention in recent years.The halide ions are simple,accessible,relatively cheap and low toxicity,which are widely used as mediator in organic electrosynthesis.For these existing problems related to the traditional methods for synthesis α-substituted ketones and indole compounds,this thesis focuses on developing the organic electrosynthesis approach with iodide as mediator to obtain these important flavors or intermediates.The major contents were listed as follows:1.The electrochemically synthesis of α-substituted ketones has been developed mediated by iodide.The reactions were carried out in a simple undivided cell using iodide as the redox catalyst under constant current condition to give the final products.Proton NMR spectroscopy,cyclic voltammetry analysis,GC monitoring and control experiments disclose the involvement of 2-iodo-l-phenylpropan-1-one as an important intermediate.A mechanism for electrochemical synthesis of α-substituted ketones is proposed.The reaction begins with the anodic oxidation of iodide to generate molecular iodine,which undergos reaction with ketones to form α-iodo ketones.Once the key intermediate is formed,it undergoes a nuclephilic substitution reaction with different nuclephiles leading to the final products.During the reaction progress,the iodide is regenerated and re-enters the redox catalyst cycle.2.The electrochemically synthesis of 3-methoxyindolines and 3-ethoxyindoline has been developed.The reactions were carried out in a simple beaker-type undivided cell with n-Bu4NI serving as a redox catalyst under constant current electrolysis(CCE)conditions.Proton NMR spectroscopy was used to monitor the process.The possible pathway was supposed to be that the amino-oxygenation of N-(2-vinylphenyl)sulfonamides likely involves the initial iodoamination of the alkene,followed by nucleophilic substitution of the methoxide/ethoxide generated at the cathode.In summary,the electrochemical synthesis of α-substituted ketones and indole compounds has been achieved by using substoichiometric amount of iodine ions as mediator.The iodide can be recycled,avoiding the utilization of external oxidants.This electrochemical method proposed is an environmently bengin process with advantages of low cost,mild reaction conditions,and simple operation.The gram-scale reaction proceeds smoothly under the standard conditions.Therefore,the electrochemical method exhibits a competitive potential in practical application In this thesis,the research enriches the electrochemical synthesis method mediated by iodide,which provides new ideas and directions for the preparation of important food flavors of α-substituted ketones and indoles.