Salicylates have been widely used for a long time in perfumery for both fine fragrance and functional applications, due to their exceptional quality.
However; they also have poor stability in basic media and they can cause allergies, leading Jean-Marc Gaudin and the Firmenich Aromatics team, based in China, to try to find a credible alternative for the perfumer's palette.
They studied a series of compounds including carba-analogues, cyclic β-keto esters and cyclic β-diketones.
Among these compounds, 1-(2-hydroxyphenyl)-3-phenyl-1-propanone (10), which can be found in nature, was identified as the most promising, due to its excellent olfactory profile and dual floral–animal note.
Gaudin and his team also mentioned that several other compounds, such as the carba-analogues 5 and 7 and the β-keto esters 27 and 28, are also worthy of interest.
“Applying the simple concept of three-dimensional structure similarity was very fruitful,” says Gaudin about the team’s tests.
The results show that the β-keto esters with a six-membered ring possess the salicylate character.
Compounds 27 and 28 were the most appreciated by the perfumers, as their odours were reminiscent of the corresponding cis-3-hexenyl salicylate and hexyl salicylate, validating their original assumption.
For the β-keto esters having a five-membered ring the results were not as good. The researchers noted that although compounds 32 and 33 have interesting odours, they do not have any salicylate character.
The olfactory evaluations of β-diketones show that these compounds are clearly not as good as the cyclic β-keto esters. Although they have the salicylate character, they also possess undesirable side notes.
The first example of salicylates in fine fragrance was probably isoamyl salicylate, discovered early on by Darzens and used in 1898 by Jacques Rouché (both at the Piver company) in the perfume ‘Trefle incarnat.’
Perfumers associate salicylates with three other very important characteristics: excellent blending properties, the great linearity of compositions in which they are present, and their blooming effect.
Interest in salicylates is not limited, however, to fine fragrance. Because of their very low prices they are particularly appreciated in functional perfumery, where their substantivities are also a great advantage.
They are commonly used in various products such as shampoo, deodorant, hair spray, soap, and sunscreen, sometimes at concentrations of up to 40 per cent.
Gaudin, J.-M. (2013), The quest for odorants having salicylate notes. Flavour Fragr. J.. doi: 10.1002/ffj.3182