Persistent perfluoroalkyl radical investigations under reductive environment: reaction with electron-donating reagents

The reactivity of persistent perfluoroalkyl radical, perfluoro-3-ethyl-2,4-dimethyl-3-pentyl (1), with various electron-donating reagents was investigated. It is revealed that 1 which is robust under oxidative conditions is rather vulnerable under reductive conditions. Thus, Lewis bases such as triethylamine and triphenylpnictogens (Ph(3)Pn, Pn=N, P, As, Sb, Bi) and some soft anions such as iodide or tetraphenyl berate reacted with 1 to give perfluoro-3-isopropyl-4-methylpent-2-ene (2) quantitatively. Even very weak Lewis bases such as diethyl ether and diethylsulfide also reacted with 1 to give 2 and additionally a hydride product, perfluoro-3-ethyl-3-H-2,4-dimethylpentane (4). Hydrogen gas did not react with 1 at all without a catalyst, but in the presence of metal Pd adsorbed on charcoal, smoothly reacted to give 2 in quantitative yield. Metal hydrides such as LiAlH4, NaBH4, NaH, BH3 (THF complex), Bu3SnH, Me2PhSiH reacted with 1 to give 2 and 4. That an electron transfer mechanism is operating in the formation of 2 is obvious, but not conclusive in the formation of 4. (C) 1999 Elsevier Science S.A. All rights reserved.