Treatment of tetrafluoroethene (TFE) with diethylzinc in the presence of lithium iodide gave 1,1,2-trifluoro-1-butene in moderate yield. In the absence of lithium iodide, however, the nucleophilic addition of diethylzinc to TFE proceeded very slowly to afford ethyl 1,1,2,2-tetrafluorobutylzinc. The addition of lithium iodide to a solution of ethyl-1,1,2,2-tetrafluorobutylzinc resulted in a smooth transformation into 1,1,2-trifluoro-1-butene. In the presence of lithium chloride, the reaction of TFE with benzyl or allyl. Grignard reagents afforded the corresponding monosubstituted products in good to excellent yields.