Mechanistic Studies on the Hexadecafluorophthalocyanine–Iron‐Catalyzed Wacker‐Type Oxidation of Olefins to Ketones**

Abstract

The hexadecafluorophthalocyanine-iron complex FePcF 16 was recently shown to convert olefins into ketones in the presence of stoichiometric amounts of triethylsilane in ethanol at room temperature under an oxygen atmosphere. Herein, we describe an extensive mechanistic investigation for the conversion of 2-vinylnaphthalene into 2-acetylnaphthalene as model reaction. A variety of studies including deuterium-and 18 O 2 -labeling experiments, ESI-MS, and 57 Fe Mössbauer spectroscopy were performed to identify the intermediates involved in the catalytic cycle of the oxidation process. Finally, a detailed and well-supported reaction mechanism for the FePcF 16 -catalyzed Wacker-type oxidation is proposed.

Iron‐Catalyzed Oxidative C−O and C−N Coupling Reactions Using Air as Sole Oxidant**

“…Thus, a reaction of 300 mg of phenol 2 f provided 7 a in 93 % yield and a gram‐scale synthesis led to 90 % yield of 7 a (entry 14). The first step in FePcF 16 ‐catalyzed reactions under air is the oxidation of the catalyst to μ‐oxobis[(hexadecafluorophthalocyanine)iron(III)] (O[FePcF 16 ] 2 ) [32] . Thus, using μ‐oxo(FePcF 16 ) 2 as catalyst under otherwise identical conditions gave a similar yield of 7 a (entry 15).…”

“…The first step in FePcF 16 -catalyzed reactions under air is the oxidation of the catalyst to μoxobis[(hexadecafluorophthalocyanine)iron(III)] (O[FePcF 16 ] 2 ). [32] Thus, using μ-oxo(FePcF 16 ) 2 as catalyst under otherwise identical conditions gave a similar yield of 7 a (entry 15). In line with our mechanistic hypothesis of a catalytic [Fe(III)]/[Fe(II)] cycle, [32] the reaction with FePcF 16 under argon (entry 16) or in the absence of any iron catalyst (entry 17) gave no conversion of the starting materials.…”

“…[32] Thus, using μ-oxo(FePcF 16 ) 2 as catalyst under otherwise identical conditions gave a similar yield of 7 a (entry 15). In line with our mechanistic hypothesis of a catalytic [Fe(III)]/[Fe(II)] cycle, [32] the reaction with FePcF 16 under argon (entry 16) or in the absence of any iron catalyst (entry 17) gave no conversion of the starting materials. In other solvents (ethyl acetate, ethanol, or acetone) the reaction was less efficient than in dichloromethane (entries [18][19][20].…”

“…However, the complex tris(dibenzoylmethanato)iron(III) (Fe[dbm] 3 ), [30] phthalocyanine–iron(II) (FePc), and hexadecafluorophthalocyanine−iron(II) (FePcF 16 ) afforded compound 7 a in 15–27 % yield (entries 4–6). The high catalytic activity of FePcF 16 for various oxidative transformations has been widely demonstrated by our group [15–18,20,31,32] . Subsequently, we have screened a range of different additives for the oxidative C−N bond formation using 4 mol% of FePcF 16 as catalyst (entries 7–13).…”

“…The high catalytic activity of FePcF 16 for various oxidative transformations has been widely demonstrated by our group. [15][16][17][18]20,31,32] Subsequently, we have screened a range of different additives for the oxidative CÀ N bond formation using 4 mol% of FePcF 16 as catalyst (entries 7-13). With methanesulfonic acid as additive (entry 7), complete decomposition of the starting material was observed.…”