Free Radical Fluorination Of Azide And The Decarboxylation Of Free Radicals To Form Olefins

A metal-free and efficient synthesis of trans-olefins via microwave-assisted direct decarboxylative elimination of arylacetic acids is described.This reaction,using commercially available reagent PIFA as oxidant,readily provided a variety of desired products in moderate to good yields.Control experiments showed that a radical process was involved in the reaction.Fluorine atoms prevail in pharmaceuticals,agrochemicals,and materials due to their unique biological,chemical,and physical properties.It is important to develop convenient methods for the synthesis of fluorine compounds.Vinyl azides,a class of unique functionalized alkenes with high intrinsic reactivity,have served as versatile synthons for numerous transformations.As an enamine-type nucleophile,vinyl azide was readily subjected to the electrophile to generate an iminodiazonium ion,followed by Schmidt-type rearrangement to form nitrilium ion,which could be intercepted by water to yield the amide.Very recently,alcohols successfully interrupted the migration to produce?-alkoxy-?-haloalkyl azides.We were drawn to the possibility that replacing alcohol with water or trimethylcyanosilane could provide an approach to synthesis of ?-fluoroketones or?-cyano-?-haloalkyl azides.The mechanistic studies indicated that a single-electron transfer(SET)and a subsequent fluorine atom transfer process could be involved in the reaction.