Manganese complex catalyst for valencene oxidation: The first use of metalloporphyrins for the selective production of nootkatone

[Display omitted] •Oxidation of valencene by O2 catalyzed by manganese porphyrins in a green solvent.•A new methodology was developed for valencene oxidation by O2 with Mn-porphyrins.•Yields of nootkatone and valencene epoxide up to 48% in 4 h.•Imidazole improves product yield in the valencene oxida...

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Bibliographic Details
Published in:Inorganica Chimica Acta 2021-01, Vol.515, p.120031, Article 120031
Main Authors: de Melo, Carla Nunes, Moreira Meireles, Alexandre, da Silva, Vinicius Santos, Robles-Azocar, Patrícia, DeFreitas-Silva, Gilson
Format: Article
Language:English
Subjects:
Acetonitrile
Chemical reactions
Citrus fruits
Green solvent
Imidazole
Manganese
Mn-porphyrins
Molecular oxygen
Nootkatone
Oxidation
Oxidizing agents
Oxygen
Porphyrins
Valencene oxidation
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Summary:[Display omitted] •Oxidation of valencene by O2 catalyzed by manganese porphyrins in a green solvent.•A new methodology was developed for valencene oxidation by O2 with Mn-porphyrins.•Yields of nootkatone and valencene epoxide up to 48% in 4 h.•Imidazole improves product yield in the valencene oxidation by O2. This work describes the oxidation of valencene, a sesquiterpene easily obtained from citrus fruits, and responsible for the fresh odor of oranges. The reactions were catalyzed by manganese porphyrins derived from 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrin (H2T3,5DMPP): [MnIII(T3,5DMPP)Cl] (MnP1) and [MnIII(Br12T3,5DMPP)Cl] (MnP2), using iodosylbenzene (PhIO), iodobenzene diacetate [PhI(OAc)2], and molecular oxygen as oxidants. The systems MnP1/O2/acetonitrile and MnP1/O2/diethyl carbonate led to higher yields of valencene oxidation products (44% and 48%, respectively) as compared with MnP2 (9% and 7%, respectively), with nootkatone being the major product. The addition of a small amount of imidazole (molar MnP1: imidazole ratio of 1:5) to the MnP1/O2/diethyl carbonate led to superior yields (64%) as compared with systems without the additive. A mechanism for the formation of the two products obtained was also proposed.
ISSN:0020-1693
1873-3255
DOI:10.1016/j.ica.2020.120031