title: Eco-friendly methodologies for the synthesis of some aromatic esters, well-known cosmetic ingredients.
abstract: Solid-liquid solvent-free phase transfer catalysis (PTC) and acidic catalysis in dry media were applied, with noticeable improvement and simplification over classical procedures in a Green Chemistry context, to the synthesis of some aromatic esters useful as cosmetic ingredients: 3-methylbutyl 4-methoxycinnamate, 2-ethylhexyl 4-methoxycinnamate, 2-ethylhexyl 4-(dimethylamino)benzoate and 2-ethylhexyl salicylate, well-known ultraviolet B sunscreen filters; 4-isopropylbenzyl salicylate, UV absorber and cutaneous antilipoperoxidant; propyl 4-hydroxybenzoate and butyl 4-hydroxybenzoate (parabens), antimicrobial agents. The reactions were performed under microwave (MW) activation and conventional heating. The best results for the synthesis of cinnamic, salicylic and 4-(dimethylamino)benzoic esters were achieved by in situ preformed carboxylates alkylation with alkyl bromides using PTC. The 4-hydroxybenzoates were obtained in good yields by classical esterification of the acid with alcohols using a simple heterogeneous mixture of reagents with catalytic amounts of p-toluenesulfonic acid (PTSA). The comparisons of yields and thermal profiles under either MW or conventional heating were studied and reported.
authors.affiliation: Dipartimento di Scienze Farmaceutiche dell'Università, Viale Benedetto XV, Genova, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Villa
authors.forename: S
authors.initials: S
authors.lastname: Baldassari
authors.forename: R
authors.initials: R
authors.lastname: Gambaro
authors.forename: E
authors.initials: E
authors.lastname: Mariani
authors.forename: A
authors.initials: A
authors.lastname: Loupy