The article reviews various olefin metathesis reactions namely self-metathesis (SM), crossmetathesis (CM), acyclic diene metathesis (ADMET) polymerization, ring closing metathesis (RCM) and ring opening metathesis (ROM) reactions for the synthesis of a variety of platform chemicals with potential industrial applications from vegetable oils and fatty acids. Different fatty acids employed for various metathesis reactions were oleic, linoleic, linolenic, eicosenoic, erucic, petroselinic, sterculic, undecenoic and ricinoleic acids, while vegetable oils used were Helianthus (sunflower), Brassica napus (rapeseed), Glycine max (soybean), Hevea brasiliensis (rubber), Butea monosperma (palash), Nicotiana tabacum (tobacco) and Sterculia foetida (jangli badam). Even though Grubbs' catalysts were employed for most of the reactions, other catalysts such as rhenium, molybdenum and tungsten based have also been used for selective reactions of vegetable oils and fatty acids. The article reviews some of the mechanistic pathways involved in the generation of unusual intermediates from fatty acids and triglycerides.

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KEYWORDSThe study signifies the importance of olefin metathesis in developing industrially important platform chemicals from a non-edible renewable resource, palash oil using Grubb's second generation catalyst. The reaction conditions were optimized by varying the concentration of the catalyst, 0.03-0.05 mM and the temperature, 45-100 °C of the reaction. Maximum yield of the metathesized products, as analysed using GC/GC-MS were obtained employing lower concentration of the catalyst, 0.03 Mm and temperature, 45 °C for 36 h. The metathesized products showed the formation of hydrocarbons namely 9-octadecene (10.9%) and cyclodecacyclotetradecene (27%) as major. The formation of cyclodecacyclotetradecene was observed for the first time. The study also describes the possible routes and the molecules involved in the formation of the metathesized products. 9-Octadecene Non-edible oils Self-metathesis Synthetic intermediates Palash fatty acid methyl esters Grubb's second generation catalyst

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Self-metathesis of 9-octadecenoic acid methyl ester was carried out with varying the concentration of Grubbs' second generation catalyst from 0.03 mmol to 0.18 mmol at 40-45 °C for 36 h. Only two products (9-octadecene 30%, and dimethyl-9-octadecene-dienoate 23%) resulted when 0.06 mmol of catalyst was employed, while at other concentrations four metathesized products were observed. 9-Octadecene generated at 0.03, 0.06 and 0.12 mmol completely disappeared and dimethyl-9-octadecene-dienoate (64%) was observed in major amounts at 0.18 mmol concentration.

The present study involves the synthesis of macrocyclic lactones by the esterification of unsaturated fatty acids (oleic acid, undecenoic acid, and erucic acid) with unsaturated alcohols (allyl alcohol, prop-2-ene-1-ol, oleyl alcohol, and undecenol) followed by a ring closing metathesis reaction employing Grubbs' second generation catalyst (1.0-1.5 mmol). The structure of the compounds was confirmed by 1H NMR, 13C NMR, FT-IR, and ESI-Mass spectral studies. The antibacterial activity of the synthesised lactones was evaluated. The larger ring-sized lactone, namely, erucic acid lactone, exhibited excellent antibacterial activity against three bacterial cell lines, namely, Staphylococcus aureus, Staphylococcus epidermidis, and Bacillus subtilis. Undecenoic acid-based lactones exhibited excellent antibacterial activity selectively against only Staphylococcus epidermidis. The assay of macrolactones for their in vitro anticancer activity was carried out by MTT for different cancer cell lines, namely, human prostate epithelial cancer cells (ATCC HTB-81), HepG2 derived from hepatic cancer cells (ATCC HB-8065), SKOV3 derived from human ovarian cancer cells (ATCC HTB-77), MDAMB-231 derived from human breast cancer cells (ATCC HTB-26) and Chinese hamster ovarian (CHO-K1) cell lines. The molecules selectively exhibited anticancer activity against Chinese hamster ovarian (CHO-K1) cell lines. Among macrolactones, (E)-oxacyclotridec-11-en-2-one (MALUN) was more active and its activity was much higher compared to others and on par with the reference standard Mitomycin C. This was followed by (E)-oxacyclotricos-14-en-2-one (MOLER) and (E)-oxacyclononadec-10-en-2-one (MOLOH). The fatty acid-based cyclic lactones with selective antibacterial and anticancer activities can be further explored for a variety of pharmaceutical formulations.

Castor (Ricinus communis) oil containing ricinoleic acid 89% was self-metathesized in the presence of Grubbs' second generation catalyst (0.025 mmol), followed by epoxidation and insitu hydroxylation using Prilezhaev dihydroxylation method to obtain hydroxylated derivatives in 93% yields. MALDI study has shown that the metathesized products comprised of a mixture of monomer, dimer and trimer metathesized products. The hydroxylated derivatives were acylated using acetic, propionic, butyric and hexanoic anhydrides in 85-90% yields. The acylated base stocks being highly branched and of high molecular weights exhibited very low pour points (− 30 to − 40 °C) and broad viscosity ranges 45.5 cSt to 60.0 cSt at 40 °C, high viscosity indices , excellent anti-wear properties (0.52-0.69 mm), good thermal and oxidative stabilities along with high load carrying capacities (165-184 kg) suitable for multi-range industrial applications. These base stocks can be used with the addition of minimum additives during the formulation.

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