4H1-08 the 98th CSJ Annual Meeting Oxidation of Aromatic Alcohols Catalyzed by Non-Heme Iron Amido Complexes ○ Takafumi Shanoh, 1,2 Hikaru Takaya, 1,2 Masato Ito, 3 Masaharu Nakamura 1,2 1 ICR, Kyoto Univ., 2 Graduate School of Engineering, Kyoto Univ., 3 IMCE, Kyushu Univ.
Non-Heme Iron Amido Complexes in Nature Fe–bleomycin complex Isopenicillin N synthase oxidation of a tripeptide into isopenicillin N oxidative degradation of DNA Gln 330 NH 2 O H N NH 2 H 2 N O O His 214 N N H H 2 O N H 2 N N Fe II O Fe II N O H 2 O N sugar H 2 N N Asp 216 N O N O 2 O peptide His 270 McNeil, L. A.; Schofield, C. J. et al. Chem. Eur. J. 2017, 23, 12815. Takita, T.; Umezawa, H. et al. J. Antibiot. 1978, 31, 1073. 1
Non-Heme Iron Amido Complex-Catalyzed Oxidation 1. Iron–TAML (tetraamido macrocyclic ligand) complex-catalyzed oxidation 2Li + 2– O O Cl N N Fe III N N O O (5 mol %) O OH O O O OH Cl Cl Cl H 2 O 2 aq (100 eq) HO + + + CO + CO 2 HO OH O NaHCO 3 /Na 2 CO 3 aq Cl Cl O OH Cl Cl 25 ºC, 9 min OH Cl 23 % 6 % 17 % 45 % Sen Gupta, S.; Collins, T. J. et al. Science 2002, 296, 326. 2. Iron–dpaq complex-catalyzed oxidation OH 2 2+ 2ClO 4– N N Fe III N N N O (5 mol %) H 2 O 2 (1.2 eq) + CH 3 CN, rt, 30 min OH OH 23 % 16 % 2 Hitomi, Y. et al. Angew. Chem. Int. Ed. 2012 , 51, 3448.
Oxidation of Aromatic Alcohols with Iron Amido Complexes This work Fe[N(SO 2 CF 3 ) 2 ] 2 catalyst O OH H 2 O 2 aq R 2 R 2 R 1 R 1 rt Fe[N(SO 2 CF 3 ) 2 ] 2 (10 mol %) N 2 SiEt 3 Et 3 SiH (2 eq) O O CH 2 Cl 2 , 40 ℃ , 48 h O O 15 % Keipour, H.; Ollevier, T. Org. Lett. 2017, 19, 5736. 3
Optimization of Reaction Conditions catalyst (10 mol %) oxidant ( x eq) OH O Ph Ph solvent, rt, 2 h yield (%) a conv. (%) a entry catalyst oxidant x (eq) solvent 1 Fe[N(SO 2 CF 3 )] 2 35 wt % H 2 O 2 aq 6 EtOAc 61 92 2 FeCl 2 •4H 2 O 35 wt % H 2 O 2 aq 6 EtOAc 26 42 3 HN(SO 2 CF 3 ) 2 35 wt % H 2 O 2 aq 6 EtOAc 0 67 5 Fe[N(SO 2 CF 3 )] 2 35 wt % H 2 O 2 aq 1 EtOAc 24 42 6 Fe[N(SO 2 CF 3 )] 2 35 wt % H 2 O 2 aq 6 MeCN 29 91 7 Fe[N(SO 2 CF 3 )] 2 35 wt % H 2 O 2 aq 6 pyridine 58 64 t BuOOH aq 8 Fe[N(SO 2 CF 3 )] 2 6 EtOAc 49 99 10 b 88 b 9 Fe[N(SO 2 CF 3 )] 2 O 2 /CH 3 CHO 6 EtOAc 10 Fe[N(SO 2 CF 3 )] 2 m CPBA 1 EtOAc 19 96 11 Fe[N(SO 2 CF 3 )] 2 PhIO 1 EtOAc 25 57 a Determined by 1 H NMR analysis. b Reaction time: 20 h. 4
Substrate Scope for Phenyl Alcohols OH Fe[N(SO 2 CF 3 ) 2 ] 2 (10 mol %) O 35 wt % H 2 O 2 aq (6 eq) EtOAc, rt, 2 h R R R yield (%) conv. (%) 61 H 92 CF 3 42 69 60 72 Cl OR’ 28 OMe >99 Ar OH O R’ = Et, Me: 5 % Ac: 3 % conv. >99 % >99 % OH O OAc + conv. >99 % 14 % 84 % 5 Yields and conversions were determined by 1 H NMR analysis.
Substrate Scope of Benzyl Alcohols Fe[N(SO 2 CF 3 ) 2 ] 2 (10 mol %) O O 35 wt % H 2 O 2 aq (6 eq) OH OH H + EtOAc, rt, 2 h conv. 96 % 56 % 8 % O O OH OH H + R R R conv. R 52 % 1 % CF 3 54 % Cl 50 % 11 % 63 % O O R R R OH OH H + O O O conv. R 38 % 16 % 85 % H 85 % OMe 8 % 3 % 6 Yields and conversions were determined by 1 H NMR analysis.
Plausible Mechanisms O H 2 O H 2 O 2 Ar R L n Fe II H + H O OH O OH Fe III L n Ar R Fe II L n Hydrogen atom H + transfer OH OH Fe III R L n Ar O H 2 O Fe IV L n OH R H Ar 7
Summary Fe[N(SO 2 CF 3 ) 2 ] 2 (10 mol %) OH O H 2 O 2 aq (6 eq) R 2 R 2 R 1 R 1 EtOAc, rt, 2 h 1. High catalytic activity toward oxidation of aromatic alcohols in the presence of H 2 O 2 2. Electron-rich aromatic alcohols showed higher substrate conversion rate. 8
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