| abstract |
Polyunsaturated cyclic compounds of formula having two double bonds conjugated in the endo- and exo positions of the pentagonal ring indicated by the dotted lines, and in which the symbols R¹ and R², taken separately, represent respectively a. a linear or branched alkyl radical from C₁ to C₄ and b. a hydrogen atom or a methyl radical, or, taken together with the carbon atoms to which they are bonded, form a polymethylenic ring as indicated by the dotted line containing from 5 to 12 carbon atoms, and the symbol R³ represents a hydrogen atom or a methyl radical, n being equal to 0 or 1, intermediate products useful for the preparation of odorous macrocyclic ketones, are prepared by vapor phase cyclization of ketones of formula in which the dotted line and the symbols n, R¹, R², R³ have the meaning indicated above, by means of a heat treatment in the presence of a cyclization catalyst consisting of an oxide of aluminum, silicon, titanium or zirconium. |