Nuove metodologie sintetiche di green chemistry per l’ottenimento di prodotti
Author(s)
Barontini, Maurizio
Date Issued
April 22, 2008
Type
Doctoral Thesis
Abstract
The research activity of this PhD course has been based on the development of innovative and
environmentally friendly synthetic methodologies using natural compounds as starting materials
and applying some principles of green chemistry.
In particular, a first aim has been the applicability of the hydrogen peroxide
(H2O2)/methyltrioxorhenium (CH3ReO3, MTO) catalytic system in ecofriendly solvents such as
ionic liquid [bmim(BF4)] and dimethyl carbonate (DMC) to perform the oxidative modifications of
a wide number of organic compounds. The obtained results showed that the above-cited oxidant
system maintained its efficiency and versatility in both solvents. Nevertheless, the use of DMC
resulted more convenient than ionic liquid for the following factors: low toxicity, more availability,
low cost, more reactivity and versatility of the oxidant system, more easy manipulation. Between
oxidized compounds, some p-benzoquinones deriving from the catalytic oxidation of phenols
resulted interesting for their tested antifungal activity against a wide number of fungi widespread in
soil and food. In some cases, they resulted more active than a commercial antifungal agent
(ketoconazole).
Subsequently, in order to perform ecofriendly processes using phenolic components present in agroindustrial
wastes, a new decarboxylation-microwave assisted of cinnamic acids to get 4-vinyl
phenols have been developed. The experimental conditions have been optimized to obtain the target
molecule in satisfactory yield. Such methodology has been also extended to samples of ferulic acid
deriving from natural extract of flecks. This experiment demonstrated the applicability of this
methodology on vegetal matrix.
The research has been continued using cinnamic acids and tyrosol as starting materials for the
synthesis of 4-aryl-3,4-dihydrocumarins, high add value-molecules. The corresponding products
deriving from the hydrolytic opening of the lactonic ring have been tested as antioxidants and
showed an higher activity than tyrosol.
To achieve these syntheses, new methodologies of selective protection of alcoholic functions
present in phenolic compounds have been optimized:
1. carbomethoxylation, using the DMC as solvent as well as reagent;
2. trifluoroacetylation with trifluoroacetic acid;
3. acetylation, using acetonitrile/chloridric acid or acetyl chloride /DMC;
4. esterification with acyl chlorides having long saturated and unsaturated chains.
The obtained products were lipophilic antioxidants more bioavailable than natural antioxidants.
Two new synthetic procedures of bioactive hydroxytyrosol have been developed. Tyrosol and
homovanillyl alcohol have been used as starting materials and some hypervalent iodine reagents
(IBX, DMP) as reagents. Such procedures, for their originality, simplicity, economic validity,
efficiency and low environmental impact, have been object of two national patents and are
promising for industrial applications.
Additional information
Dottorato di ricerca in Scienze ambientali
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