In the ethenolysis of the renewable raw material ricinoleic acid methyl ester the valuable oleochemical key substance methyl dec-9-enoate is produced. Detailed optimizations lead to a high conversion and yield of the desired product. Another interesting product, the dec-1-ene-4-ol, is built by this reaction as coproduct. The products are accessible under mild reaction conditions and with the use of only small amounts of a commercial available homogeneous ruthenium catalyst. The results obtained are also achievable in the ethenolysis of ricinoleic acid and castor oil, under the same mild reaction conditions.