Green chemistry procedure for the synthesis of cyclic ketals from 2-adamantanone as potential cosmetic odourants.

Some cyclic ketals derived from 2-adamantanone were obtained in excellent yields by microwave activation under solvent-free conditions, as a 'green chemistry' procedure. A number of experiments were performed to evaluate the most efficient catalytic conditions. The best results were obtained using a simple heterogeneous mixture of reagents and p-toluenesulphonic acid as the catalyst, without any solvent or support. The data are reported and compared with those obtained by other microwave-mediated syntheses or by classical method. In order to check the possible intervention of non-thermal microwave effects, the best experiment in 'dry media' was carried out with considerable lower yield by conventional heating, in a thermostated oil bath, under the same conditions as under microwaves (time, temperature and vessel). All the synthesized compounds were tested for their olfactive character and for a potential cosmetic use. The odour evaluation is reported.