Iron tetraphenylporphyrin epoxides

Synthetic iron porphyrin complexes such as Fe(TPP) (tetraphenylporphyrin = TPP), Fe(TMP) (Tetramesitylporphyrin = TMP), and Fe(TDCPP) (tetrakis (dichlorophenyl)porphyrin = TDCPP) (Fig. 9) have been used as models for P450 and peroxidase (9, 50-54). Early pioneering work showed that epoxida-tion catalyzed by Feln(TPP) was successfully carried out by the use of iodosylbenzene (Ph—1=0) as an oxidant (50). A very interesting feature of this model epoxidation is that the cis olefin is readily oxidized while the trans olefin is hardly oxidized (e.g., d.v-stylbene can be oxidized in 80% yield, but fraws-stylbene gave only a trace amount of the epoxide under the same conditions) (50, 55). Most of the model reactions are carried out in homogeneous organic solvents such as chloroform, dichloromethane, and acetonitrile, thus, the c/.v-epoxidation is expected to be a kinetically favorable process over the trans-epoxidation. 

Two new tetraphenylporphyrin (TPP) catalysts have been reviewed.331 Cr(TPP)m triflate is highly regio- and stereo-selective in rearranging epoxides into aldehydes, while the iron perchlorate analogue affords the corresponding ketones. 

Iron(III) tetraphenylporphyrin, Fe(TPP)OTf, is an efficient catalyst for the regioselec-tive rearrangement of simple monoalkyl-substituted epoxides into the corresponding aldehydes (Sch. 9) [59],... 

In 1979, Groves and co-workers published the first article on the use of a synthetic iron(III) porphyrin complex, Fe(TPP)Cl (TPP = weio-tetraphenylporphyrin), in catalytic olefin epoxida-tion and alkane hydroxylation reactions by iodosylbenzene (PhlO). Olefins were preferentially oxidized to the corresponding epoxides, and alcohols were obtained as major products in alkane hydroxylations (Equations (3) and (4)) ... 

Groves and coworkers [45] were the first to translate these results to a model system. They described the use of iron(III) meso-tetraphenylporphyrin (TPP) chloride in combination with iodosylbenzene for the epoxidation of olefins and hydroxylation of alkanes. Subsequently, chromium [46] and manganese [47] TPP complexes were shown to catalyze oxygen atom transfer from PhIO to an olefin or an alkane. 

Figure 3 Turnover numbers of three iron meso-tetraphenylporphyrins catalyzing the epoxidation of norbomene...

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