The selective functionalization of saturated hydrocarbons. Part 32. Distinction between the Fe^II–Fe^IVand Fe^III–Fe^Vmanifolds in Gif chemistry. The importance of carboxylic acids for alkane activation. Evidence for a dimeric iron species involved in Gif-type chemistry

Iron-catalysed oxidation and halogenation of organic matter in nature

“…Alternatives may involve halide oxidation, as recently studied with two non-heme iron model complexes, [141] or typical Gif chemistry as discussed below. [142] Importantly, there are recently published observations that the so-far generally assumed rebound mechanism for non-heme iron model systems (see Fig. 7) is at least in one case not relevant.…”

“…Postulated mechanisms for the hydroxylation and halogenation of hydrocarbons by Gif chemistry are shown in Eqns 37 and 38. [142,149] ϩRH…”

Oxygenation of Hydrocarbons Mediated by Mixed-Valent Basic Iron Trifluoroacetate and Valence-Separated Component Species under Gif-Type Conditions Involves Carbon- and Oxygen-Centered Radicals

“…This further argues in support of a central role for the Fe II /H 2 O 2 combination in generating the active oxidant. In a reinterpretation of the Gif mechanism, Barton et al [23] had accepted that the Fe II /H 2 O 2 ªmanifoldº (as opposed to Fe III /H 2 O 2 ) produces substrate-based alkyl radicals, but maintained that the active oxidant is Fe IV O.…”

Selective Allylic Hydroxylation of Octahydronaphthalene Derivatives with a Bridgehead Double Bond Using Electrochemical Method with Iron Picolinate Complexes

“…1-3) Many investigations on biomimetic oxygenation systems using iron(III) picolinate (Fe III (PA) 3 ) or iron(II) picolinate (Fe II (PA) 2 ) complexes as catalysts have been reported under various conditions and in various solvents, [4][5][6][7][8] but direct 7a-hydroxylation is not easy and most reported allylic hydroxylations involve multistep reactions via other functionalized compounds [9][10][11][12][13][14] or afford low yield or stereoselectivity. [15][16][17] We have been developing a 7a-hydroxylation system for steroids, [18][19][20] and we reported in a preceding paper that the combination of electrolysis and the Fe III (PA) 3 /O 2 /CH 3 CN system gave good results in the hydroxylation of cholesteryl acetate.…”

“…

Oxygenation reactions are very important in steroid metabolism and biosynthesis.1-3) Many investigations on biomimetic oxygenation systems using iron(III) picolinate (Fe III (PA) 3 ) or iron(II) picolinate (Fe II (PA) 2 ) complexes as catalysts have been reported under various conditions and in various solvents, [4][5][6][7][8] but direct 7a-hydroxylation is not easy and most reported allylic hydroxylations involve multistep reactions via other functionalized compounds [9][10][11][12][13][14] or afford low yield or stereoselectivity. [15][16][17] We have been developing a 7a-hydroxylation system for steroids, [18][19][20] and we reported in a preceding paper that the combination of electrolysis and the Fe III (PA) 3 /O 2 /CH 3 CN system gave good results in the hydroxylation of cholesteryl acetate.

21)

On the other hand, functionalization, especially oxygenation, of octahydronaphthalenes or decalin derivatives is also very important because many bioactive or natural compounds contain a skeleton resembling the AB fused ring of cholesterol.

22-24) Therefore, we wished to identify the required structural factors for regio-and stereoselective direct 7a-hydroxylation of steroids by our electrochemical method, as well as to extend the range of applicability of this method for allylic a-hydroxylation of small cyclic compounds.

In this report, we describe the iron picolinate-induced hydroxylation reactions of octahydronaphthalene derivatives 5b, 6b and 7b as simple models for allylic oxygenation of steroids or other decalin derivatives.

Results and Discussion

The substrates 5b-7b were prepared by benzoylation of the corresponding octahydronaphthalenols 5a-7a.

…”