低原子価ニオブ種による炭素-フッ素結合の触媒的活性化反応

抄録

It was found that low-valent niobium species, which is generated from niobium(V) chloride and lithium aluminum hydride, in situ, is an efficient catalyst for activation of carbon-fluorine bonds. The low-valent niobium species catalyzed 1) hydrodefluorination of fluorobenzenes and α,α,α-trifluorotoluenes, and 2) intramolecular C-C coupling reactions of o-aryl-, o-alkenyl-, and o-alkylamino-α,α,α-trifluorotoluenes. In the latter reactions, fluorenes, indenes, and N-fused indoles were synthesized catalytically in good yields. Nb(0) is supposed to be an active species. Deuterium labeling experiments suggest that niobium fluorocarbenoid intermediates are generated from α,α,α-trifluorotoluenes in the latter C-C coupling reactions.