The search for less expensive routes to synthetic macrocyclic ketones as replacements for natural musk odorants has been studied by various groups for some time. The 15-, 16-, and 17-membered cyclic ketones have desirable odor and fixative properties. The 18-member ketone has an attractive odor but is weaker than that of the 15-17 member rings and at the present time is not of commercial interest. It has good fixative properties which, in the case of toluene, were shown to be due to the formation of a surface-covering of crystalline ketone when the concentration of the ketone reached a critical level of approximately 82%.
Many of the routes to the 15- and 16-member rings are based on the expansion of the cyclododecanone ring. While tbe chemistry is often quite elegant, each of these procedures involves a number of steps and tend to be tedious and costly.
Another process is based on the acyloin condensation of long chain diesters. This route is made more attractive by the increased availability of the dicarboxylic acids through microbial oxidation of n-alkanes, metathesis of olefinic esters, and sources not identified.
