Homogenous catalytic conjugation of polyunsaturated fats by chromium carbonyls

Various arene‐Cr (CO) 3 complexes and Cr(CO) 6 are effective soluble catalysts for the conjugation of polyunsaturated fats. Methyl benzoate‐Cr(CO) 3 is one of the most active catalysts. The following conjugation levels were obtained: methyl linoleate, 65%; methyl linolenate, 45%; the polyunsaturates in soybean and safflower oils, 73%; and in linseed oil 48%. Conjugated dienes from linoleate were predominantly cis,trans in configuration. Their double bonds were distributed between C 5 and C 16 of the fatty acid chain. Hydrogenation and dehydrogenation are side reactions, which seem to limit the yield of conjugated dienes from methyl linoleate. A conjugation mechanism is proposed that involves allyl‐HCr(CO) 3 complexes as intermediates undergoing 1,3‐ and 1,5‐hydrogen shifts.