Synthesis of hyacinth, vanilla, and blossom orange fragrances: the benefit of using zeolites and delaminated zeolites as catalysts

The synthesis of phenylacetaldehyde glycerol acetals, 2-benzyl-4-hydroxymethyl-1,3-dioxolane (1), 2-benzyl-5-hydroxy-1,3-dioxane (2), and vanillin propylene glycol acetal (2-(4-hydroxy-3-methoxyphenyl)-4-methyl-1,3-dioxolane) (3) which are flavoring compounds with hyacinth and vanilla scent fragrances, have been carried out successfully by acetalization of phenylacetaldehyde and vanillin with glycerol and propylene glycol, respectively, using toluene as solvent and zeolite catalysts whose adsorption properties have been optimized. However, in the case of a larger size acetal such as 2-acetonaphthone propylene glycol acetal (4) with blossom orange scent, geometrical constraints make the diffusion of reactants and products inside the micropores more difficult. In this case, a delaminated zeolite (ITQ-2) with very large and structured external surface is an active and selective catalyst. Furthermore, the delaminated zeolite allows the reaction to be carried out in a solvent-free system, opening the possibility for an environmentally friendly process for the synthesis of acetal fragrances.