Iron(II)-Induced Activation of 1:1 HOOH/HCl for the Chlorohydroxylation of Olefins and the Chlorination of Hydrocarbons: Chlorinated Fenton Chemistry

Abstract

Iron complexes [Fen(0PPh3)d2+, Fen(bpy)2?+, Fen(OH2)62+, and FeT131 catalytically activate 1 : 1 HOOW HC1 combinations for the efficient chlorohydroxylation of olefins. The reactive intermediate 7 is not HOC1, but appears to be formed via a Fenton process FenLX2+ (B) [LfFenOOH(BH+)] (1) -(HCl) [LXFe"(OH)C1] (7) + H20). Although the major product from the reaction of 7 with olefin substrates (e.g., cyclohexene, c-C&IIO) is the chlorohydroxo derivative [c-C&o + HOOH + HC1-(FenLx) c-C6Hlo(OH)Cl+ H20], significant amounts of the dihydroxo [ c -C~H~~( O H )~]and traces of the dichloro [ C -C~H~O C~~] derivatives are produced. The reaction efficiency with respect to H O O W C l ranges from 51% for norbornene to 31% for cyclohexene to 10% for 1-hexene. The presence of dioxygen ( 0 2 ) with c-C~HIO results in the production of some ketone [c-C&lg(O)] via oxygenated Fenton chemistry, but does not inhibit the chlorohydroxylation process. The catalyzed process is equally efficient and selective in a biphasic HzOhubstrate solution as in acetonitrile. With cis-stilbene (cis-PhCH=CHPh) the major product is the epoxide ('80%); the reaction efficiency is 63% relative to HOOWCl. These systems chlorinate saturated

Mechanism of Electrochemical Generation and Decomposition of Phthalimide-N-oxyl

“…The redox response of NHPI at a glassy carbon electrode was measured in anhydrous MeCN with recrystallized tetrabutylammonium hexafluorophosphate (NBu 4 PF 6 ) Figure A shows the voltammetric response of NHPI without base in the electrolyte.…”

“…The redox response of NHPI at a glassy carbon electrode was measured in anhydrous MeCN with recrystallized tetrabutylammonium hexafluorophosphate (NBu 4 PF 6 ). 12 Figure 2A shows the voltammetric response of NHPI without base in the electrolyte. In contrast to numerous previous reports, including our own, 4−7,13,14 a reversible voltammetric response was not observed.…”

Reactions of C−H Bonds in Water

“…105 Fe(II)-(O)(PPh 3 ) 4 was used as a coupling catalyst with H 2 O 2 /HCl as an oxidant system in water or MeCN. However, only lower conversions (∼20%) were observed.…”

Chemistry of Reactive Oxygen Species

“…In the initial study, was used also as an oxidant and in subsequent investigations many different transition-metal ions and their complexes have been employed. The mechanism of this system is still a subject of active investigation (Bakac and Espenson, 1983;Koppenol, 1985;Moffett and Zika, 1987;Eberhardt and Colina, 1988;Masarwa et al, 1988;Johnson et al, 1988;Sawyer et al, 1993Sawyer et al, , 1995Wink et al, 1994b;Kawanishi et al, 1994;Shi et al, 1994a;Gunther et al, 1995;Pogozelski et al, 1995;Buettner and Jurkiewicz, 1996;Held et al, 1996;Biaglow et al, 1996). The two basic competing mechanisms were proposed in the early 1930s (Koppenol, 1993) the first of which has the release of a free hydroxyl radical into the solution, and the second of which involves the formation of the iron(IV)-oxo ion, Hydrogen peroxide reacts preferentially with transition-metal ions by one-electron transfer (Bakac and Espenson, 1983).…”

“…An intriguing perturbation on Fenton chemistry has been suggested recently. Under appropriate conditions, Fe(II) complexes interact with and HCl to bring about the chlorohydroxylation of alkenes (Sawyer et al, 1995). The prevalence of in the physiological milieu suggests that this chemistry should be investigated further.…”