Fluorocarbon-aluminium compounds. V. Reactions of some fluorotoluene compounds with lithium tetrahydroaluminate

Abstract

In tetrahydrofuran at -45° and in diethyl ether at 20°, the reaction of α-bromo- 2,3,4,5,6-pentafluorotoluene with lithium tetrahydroaluminate yields 2,3,4,5,6-penta-fluorotoluene. In tetrahydrofuran at 20°, the same reaction occurs initially but the pentafluorotoluene then reacts further with LiAlH₄. LiAlH₄ attacks the para-fluorine atom of 2,3,4,5,6- pentafluorotoluene to form 2,3,5,6-tetrafluorotoluene and the fluoro- carbon-alane complex LiAl(C₆F₄CH₃)H₂F. The reaction between LiAlH₄ and C₆F₅CH₃ is complete after 0.5 hr at 65°. In turn, 2,3,5,6- tetrafluorotoluene reacts with LiAlH₄ in refluxing tetrahydrofuran to form the fluorocarbon-alane complexes LiAl(C₆F₄CH₃)_nH_4-n, n = 1-3.     The fluorocarbon-aluminium compounds have not been isolated from solution but were characterized by quantitative determination of the products of hydrolysis and by ¹H and ¹⁹F N.M.R. spectroscopy.