In the presence of trifluoromethylsulfonium reagents,b oronate complexes derived from 2-lithio furan and non-racemic secondary and tertiary alkyloraryl boronic esters undergo deborylative three-component coupling to give the corresponding 2,5-disubstituted furans with excellent levels of enantiospecificity.T he process proceeds via the reaction of boronate complexes with at rifluoromethyl radical, which triggers 1,2-metallate rearrangement upon single-electron oxidation. Alternative electrophiles can also be used in place of trifluoromethylsulfonium reagents to effect similar threecomponent coupling reactions.Transition-metal-catalyzed stereoselective sp 2 -sp 3 cross-coupling reactions of secondary alkyl organoboron reagents with aryl halides attract considerable interest owing to the importance of populating drug-discovery libraries with molecules containing 3D structural motifs.[1] However,t he slow rates of both the transmetalation and the reductive elimination steps associated with these types of cross-coupling reactions have hindered progress.Although several advances have been charted in this challenging area, [2] we recently developed ac onceptually different, transition-metal-free cross-coupling reaction, [3] which enables the stereospecific coupling of non-racemic secondary and tertiary alkylboronic esters [4,5] with aw ide range of aryl lithium reagents (Scheme 1A). Ther eaction involves initial formation of aryl boronate I through Li-B exchange of an aryl lithium and an alkylboronic ester.[6] Subsequent addition of an electrophilic halogenating agent (NBS = N-bromosuccinimide) to I forms oxocarbenium II (structure drawn for clarity although aconcerted mechanism has been proposed), [3b] which promotes a1 ,2-metallate rearrangement giving the neutral boronic ester III.F inally,r earomatization-driven elimination of the halide and the boronic ester group generates the substituted aryl product. We reasoned that this useful methodology could be substantially expanded by using carbon-based electrophiles in place of halogenating agents,asthen the intermediate akin to boronic ester III (boronic ester V,S cheme 1B) would not undergo elimination, thus enabling not one,b ut two CÀCb onds to be formed in the process.S ubsequent oxidative rearomatization would lead to high-value aromatic products derived from three components.We initially considered using trifluoromethyl-based electrophiles because this group has found widespread utility in pharmaceuticals,e ndowing molecules with more attractive levels of bioavailability and membrane permeability relative to the hydrocarbon-based parent compounds.[7] Indeed, new methods to introduce the trifluoromethyl group have received considerable attention in recent years. [8] We recognized the potential application of electrophilic trifluoromethylation [9] in our proposed three-component coupling reaction, which would provide access to enantioenriched trifluoromethylated furans,amotif that has been incorporated into potential drug candidates targeting the treat...