On Biomimetics by Lilyana Pramatarova

On Biomimetics
182

mechanism. The steric volume of the β-substituents may hinder the formation of the μ-
peroxo dimmer intermediate and reduce the activity of M[D(β-X) 2 PDME].

012345

0

4

8

12

16

20

time (h)

Yield (%)

Fig. 13. Yields of cyclohexanol and cyclohexanone in the oxidation of cyclohexane catalyzed
by M[D(β-Br) 2 PDME]. Reaction conditions: cyclohexene 1000 mL, catalyst 0.02 mmol,
temperature 150 Ԩ, Pressure 0.8 MPa, Co(II)D(β-Br) 2 PDME;
ClMn(III)D(β-Br) 2 PDME; ClFe(III)[D(β-Br) 2 PDME] (■).

Catalyst t (h) C (%) S (%) n(Alcohol)/n(Ketone) TON

ClFe(III)[D(β-NO 2 )PDME] 4.5 12.5 93.4 0.9 57212

ClFe(III)[D(β-NO 2 ) 2 PDME] 4.5 13.9 92.2 1.0 63620

Co(II)[D(β-NO 2 )PDME] 3.5 18.8 90.5 1.2 86048

Co(II)[D(β-NO 2 ) 2 PDME] 3.5 19.4 89.6 1.4 88794

ClMn(III)[D(β-NO 2 )PDME] 4.0 15.1 91.3 1.2 69113

ClFe(III)[D(β-Br) 2 PDME] 4.0 16.60 91.8 1.6 75978

ClMn(III)[D(β-Br) 2 PDME] 3.5 23.57 87.6 1.3 107880

Co(II)[D(β-Br) 2 PDME] 4.0 21.24 88.5 2.7 97215

Co(II)[D(β-I) 2 PDME] 4.0 14.95 91.2 1.8 68426

Table 5. Results of the oxidation of cyclohexane catalyzed by M[D(β-X) 2 PDME].

5.4 Oxidation of cyclohexane catalyzed by 13,17-modified metallo-deuteroporphyrin
derivates
The oxidation of cyclohexane with air in the absence of additives and solvents was also used
as a probe to investigate the catalytic properties of the 13,17-modified M(DPD) complexes,
including metallo-deuteroporphyrin diethyl ester [M(DPDEE)], metallo-deuteroporphyrin
dipropyl ester [M(DPDPE)], [M(DPDOE)], metallo-13,17-dibromodeuteroporphyrin
[M(DBDP)] and metallo-13,17-dichlorodeuteroporphyrin [M(DCDP)]. Table 6 shows the
results of oxidations of cyclohexane in the presence of 13,17-modified M(DPD), where M =
Co. It may be seen that in the case of cobalt porphyrins, introduction of electron-
withdrawing substituents at the 13-/17-position have virtually no effect on the cyclohexane
oxide conversion, which is not in agreement with earlier observation for β-substituted
M(DPDME)-catalyzed hydrocarbon oxidations. Conversely, the ratio of cyclohexanol to
cyclohexanone is extremely sensitive to the influence of electron-withdrawing groups in the