The invention concerns an improved process for the preparation of macrocyclic products with 12 or more ring atoms containing one or more polar functional groups on the ring and/or one or more heteroatoms within the ring by ring closing metathesis (RCM) of suitably substituted diene precursors even if the substrates are devoid of any kind of conformational preorganization. Metal carbene complexes of Ru, Mo, W, Re, Os, which are tolerant towards the respective functional group and can either be isolated or prepared in situ are used as catalysts or catalyst precursors. Preferred catalysts or catalyst precursors are ruthenium complexes of the general type XX.sub.1 LL.sub.1 Ru.dbd.CRR.sub.1, wherein X, X.sub.1 =halogen, L, L.sub.1 =trialkylphosphine, R, R1=H, Ph, CH.dbd.CPh.sub.2 denote the most preferred embodiment. The process can be applied to the synthesis of olfactory compounds, perfumary ingredients, pheromones, crown ethers, antibiotics and pharmaceuticals for human and veterinary medicine.