フルオロアルケニルヨードニウム塩を利用したフルオロアルケンの立体選択的合成

概要

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Stereoselective synthesis of fluoroalkenes is described. The reaction of alk-1-ynes with p-iodotoluene difluoride under acidic condition gave (E)-2-fluoroalkenyliodonium salts stereoselectively in good yields. On the other hand, (Z)-2-fluoroalkenyliodonium salts were synthesized efficiently by Michael-type addition of hydrogen fluoride onto alkynyliodonium salts, which can be readily prepared from alk-1-ynes. By using the fluoroalkenyliodonium salts, a variety of fluoroalkenes were synthesized stereoselectively. For example, palladium-catalyzed cross-coupling reactions of the fluoroalkenyliodonium salts gave various fluoroalkenes . By treatment of the fluoroalkenyliodonium salts with potassium tert-butoxide at room temperature, 1-fluorocyclopentenes were synthesized in good yields via 1, 5-C-H insertion of α-fluoroalkylidenecarbenes, which were generated by α-elimination of the hydrogen atom and aryliodanyl group of the fluoroalkenyliodonium salts. Finally, the reaction of the fluoroalkenyliodonium salts with lithium diisopropylamide at low temperature generated α-fluoroalkylidenecarbenoids, which could be trapped with trialkylboranes to give 2-fluoroalkenylboranes stereoselectively. The fluoroalkenylboranes could be used for further fluoroalkene synthesis.