Transition-metal trifluoromethane-sulphonatesrecyclable catalysts for the synthesis of branched fatty derivatives by Diels-Alder reactions at unsaturated fatty esters Diels-Alder reactions of conjugated linoleic acid ethyl ester (1) with different quinones and with a variety of α/β-unsaturated aldehydes and ketones are described in this paper. Using Sc(OTf) 3 or Cu(OTf) 2 as catalysts the reactions can be carried out at 25-40°C with good yields. For the first time in oleochemistry it is possible to prepare Diels-Alder cycloadditions with catalyst concentrations of 10 mol-% instead of stoichiometric amounts of Lewis acids. Furthermore, the reaction time was partly shortened drastically. The catalyst Sc(OTf) 3 can be removed by a simple extraction of the organic layer with water. After evaporation of the aqueous phase to dryness the catalyst can be reused without loss of yield.

During the irradiation of phenol (1) with 15N‐enriched tetranitromethane in acetonitrile, and during the reaction of 1 with 15N‐enriched nitric acid and nitrous acid, emission due to the nitration products o‐ and p‐nitrophenol (2a, 2b) is observed in the 15N‐NMR spectra. The CIDNP effects are built up by radical pairs formed by the encounters of the radicals NO2· and 1+· or PhO·. During the reaction of 1 with nitrous acid, 2b is formed, in part due to a non‐radical reaction, via oxidation of p‐nitrosophenol (3).

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Diels‐Alder reactions of conjugated linoleic acid ethyl ester (1) with different quinones and with a variety of α/βunsaturated aldehydes and ketones are described in this paper. Using Sc(OTf)3 or Cu(OTf)2 as catalysts the reactions can be carried out at 25—40 °C with good yields. For the first time in oleochemistry it is possible to prepare Diels‐Alder cycloadditions with catalyst concentrations of 10 mol‐% instead of stoichiometric amounts of Lewis acids. Furthermore, the reaction time was partly shortened drastically. The catalyst Sc(OTf)3 can be removed by a simple extraction of the organic layer with water. After evaporation of the aqueous phase to dryness the catalyst can be reused without loss of yield.

During the photochemical nitration of phenol, 3,5-dimethylphenol and 1,2-dimethoxybenzene (8) with ' 5 N-enriched tetranitromethane, the ' 5 N nuclear magnetic resonance (NMR) signals of the nitro products 2-nitrophenol, 4-nitrophenol, 2-nitro-3,5-dimethylphenol, 4-nitro-3,5-dimethylphenol and 1,2-dimethoxy-4-nitrobenzene (9) appear in emission. The nuclear polarizations are built up in radical pairs formed by radical cations or in case of the phenols by phenoxyl radicals and 'NO 2 . They are generated by photoreactions from excited triplet states of the reactants or by free radical encounters. With 8, I,2-dimethoxy-4-trinitromethylbenzene is also formed which slowly converts to 9. In contrast to this, the ' sN NMR signals of the nitration products of anisole (11) and 3,5-dimethylanisole (12), 2-nitroanisole, 4-nitroanisole, 3,5-dimethyl-2-nitroanisole and 3,5-dimethyl-4-nitroanisole appear in enhanced absorption indicating the appearance of singlet radical pairs [11 , 'NO 2 1s and [12,'NO2] s in which the nuclear polarizations are built up. The singlet radical pairs are formed by decomposition of an unstable intermediate, most probably a nitro-trinitromethyl adduct.