The invention relates to compounds of the general formula
in which R1 to R7 are, independently, H, methyl or ethyl, R8+R9 represent methylene (-CH2-) or a single bond, or R1+R2 represent -(CH2)n-, with n being 3 or 4, or R3+R5 or R5+R7 represent methylene or a single bond; and the presence of at least one cyclopropane ring in the molecule is compulsory and the side chain can be saturated or contains one double bond in position α,β or β,γ,
a process for the manufacture of these compounds, compounds used to perform the process and the use of these compounds as an odorant or as an ingredient of an odorant composition.
A process for the cyclopropanation of a substituted alkene, comprising the reaction of the alkene with a carbenoide, generated from dibromomethane and a tri-(C
2
-C
8
)-alkyl aluminium compound, in the presence of a catalytic amount of a metal compound selected from the group consisting of Lewis acids, metallocenes and metal carbonyl complexes. The process advantageously uses transition metal compounds as catalysts and the dibromomethane can be recovered.
The process is especially useful for the preparation of ingredients for the flavour and fragrance industry.