Study On The Synthesis Of 1,2,3-Thiadiazole And ?-Methylation Of Ketone Based On Electrochemical Dehydrogenative Coupling Strategy

Dehydrogenative coupling is one of the most direct methods to construct new chemical bonds.It reacts directly through the R-H bond of substrates without pre-functionalization of substrates.It greatly shortens the synthesis steps and is one of the most economical methods in organic synthesis.However,traditional dehydrogenative coupling requires more than equivalent oxidants to promote the dehydrogenative process,and the use of a large number of chemical oxidants is prone to produce by-products.The electrochemical dehydrogenative coupling method promotes electron transfer through electrodes,avoids the use of external oxidants,greatly improves the efficiency of the reaction,and has many advantages such as mild reaction conditions and high regioselectivity.In this paper,the synthesis of 1,2,3-thiadiazoles and?-methylation of ketones were studied by electrochemical dehydrogenative coupling strategy.(1)Thiadiazole derivatives are a class of compounds with broad pharmacological activities,such as antimicrobial,antiviral and antineoplastic activities,which are widely used in drugs and materials.In this paper,a method for the synthesis of 1,2,3-thiadiazoles by dehydrogenative coupling under electrochemical conditions using sulfur and benzenesulfonylhydrazide as raw materials was studied.The results of cyclic voltammetry showed that the key of the reaction was that the iodine anion were oxidized to produce elemental iodine under the action of electrodes,and then formed active intermediates with the substrates hydrazone.In addition,this method uses ammonium iodide as the sole electrolyte and catalyst.It has the advantages of no transition metal and oxidant,wide adaptability of substrates and high yield.It is a new clean and environmentally friendly synthesis method.(2)Methylation of C(sp~3)-H bond is a basic chemical transition in C-H bond functionalization,and also a hot topic in organic functional group research.In this paper,the?-methoxy methylation and?-amine methylation reaction of ketone were directly carried out by phenylacetone and methanol using electrochemical oxidation dehydrogenative coupling strategy.Methanol is used as methylation reagent in the reaction,which has the advantages of environmental protection,atomic economy and step economy.At the same time,?-amine methylation reaction of ketone can be achieved directly by adding nitrophilic nucleophilic reagent in"two-step,one-pot method".The main characteristics of this method are no need of external oxidants,simple operation,low cost and easy availability of reaction materials,clean and pollution-free.