Iron-catalyzed Olefin Production Of Imines Via Carbon-carbon Double Bond Cleavage

The imine motif commonly exists in various drugs and natural molecules,and its typical carbon-nitrogen double bond possesses high chemical reactivity,which can realize many types of structural transformation under different reaction conditions.Therefore,imine compounds are often used as important intermediates or starting materials for the synthesis of nitrogen-containing molecules.Although there are many reported methods for the synthesis of imines,including the one-step strategies from a variety of simple starting substrates,there is no method to synthesize imines by breaking carbon-carbon double bonds with olefins as raw materials.On the other hand,most common strategies of breaking the carbon-carbon double bond require the stoichiometric amount of oxidants,which are not only causing the environmental impact but also limit their application in oxygen-sensitive compounds.For these reasons,we have successfully developed a green and efficient method for the preparation of imine derivatives by using olefins as raw materials and aryl azides as the nitrogen source.Using cheap ferrous chloride as the catalyst can cleaved smoothly the carbon-carbon double bond of 4-hydroxystilbenes to afford the desired carbon-nitrogen double bonds in one step.Notably,N₂ is the sole byproduct in the transformations.The result of the substrate scope shows that the 4-hydroxystilbenes with diverse kinds of substitutents can successfully achieve the target conversion with up to 95%yield.However,the method is still only applicable to aryl azides as the nitrogen source.In terms of method application,as there is no external oxidant in the reaction,this strategy can be combined with Heck-Matsuda coupling reaction to achieve the carbon-carbon double bond cleavage of complex unactivated olefins,and it has very high compatibility with oxygen-sensitive groups.It is also beneficial to simple and mild reaction conditions.After the imine products formed,the target reaction can be used in series to perform a"one-pot"conversion without any postprocessing,which affords a variety of complex nitrogen-containing molecules efficiently.On the basis of experimental observations,a plausible mechanism involving nitrene transfer with the radical property is also proposed.