Boron trichloride (BCl3)–MeOH can be used for the methylation of cyclopropane FAs with satisfactory results, and it should be used in preference to BF3–MeOH, which reacts with di-substituted cyclopropanes to give methoxy derivatives and olefins [309]. BCl3 is usually milder than BF3 [310,311]. However, transesterification with BF3–MeOH from glycerides, phosphatides, and cholesterol esters to methyl esters was reported to be more successful than with BCl3–MeOH [312]. Artefacts produced during methylation with boron trihalides have been reported [313–319]. Six methylation methods were compared by Medina et al. [319] and support the fact of artifact production. The use of BF3–MeOH gave a lower content of 18:1 (n = 9) than the other methods and produced an artifact. Rotzsche [320] has found that fatty acid salts can be methylated directly without prior acidification. BF3–MeOH methylation is a popular method. Interesting remarks on methylation with boron trifluoride have been published by Ackman [321]. Boron tribromide is described as a catalyst in transesterification with alcohols other than methanol [322], but is not widely used.