Green Chemistry and Technology

Olefi n metathesis is a powerful and versatile green method in synthetic organic and polymer chemistry. Th ese reactions in general are very selective and require mild reaction conditions as well as low catalyst loadings. Th e atom economy of these synthetic procedures is often 100% indicating that all the starting materials are incorporated into the end products. Cross metatheses of a non-edible vegetable oil, the tung oil or α–eleostearic acid (ESA) methyl ester (1) with cis-1,4-diacetoxy-2-butene (2) using Hoveyda-Grubbs (3-HG2), Grubbs second or third generation catalysts (3-G2 or 3-G3), followed by Pd/C catalysed hydrogenation, gives methyl (ω) 11-acetoxy-undecanoate (4) as a polyester raw material, 1,6-hexanediol diacetate (5), the precursor of 1,6-hexanediol polyurethane monomer and heptyl acetate as a fragrance (6) in 51-99% yields. The onepot

isomerisation of the isolated double bonds containing vegetable oils

such as α–linolenic acid (ALA) methyl ester (7) using RuHCl(CO)(PPh3)3 catalyst followed by in-situ cross-metathesis (CM) of the reaction mixtures with 2 using 3-G2 leads also to the formation of 5 and the homologs of 4 and 6. Th us, in the latter approach, the key step of the synthesis of 5 is the one-pot isomerization of the isolated double bonds of 7 into conjugated ones in combination with a subsequent cross-metathesis using crosscoupling agent 2.