Selective synthesis of fluorinated furan derivatives via AgNO3-catalyzed activation of an electronically deficient triple bond.

The transition metal-catalyzed direct activation of electron deficient triple bonds was investigated by using the combined electron withdrawing effects of two fluorine atoms to modulate the electronic density of the triple bond. With use of catalytic amounts of AgNO3 (10 mol %) the synthesis of substituted 3,3-difluoro-4,5-dihydrofurans from gem-difluorohomopropargyl alcohols occurred in excellent NMR yields. Treatment of these dihydrofurans with SiO2 or Pd/H2 yielded the corresponding 3-fluorinated furans and 3,3-difluorotetrahydrofurans.