Synthesis of 2-oxazolines proceeding from dehydroabietic and 12,14-dinitrodehydroabietic acids

The first three-step synthesis of 2-oxazolines was accomplished using dehydroabietic and 12,14-dinitrodehydroabietic acids. It was shown that the intermediate secondary amides containing fragments of ethanolamine, valinol, tryptophanol, phenylalaninol, and methyl l-serinate can be directly converted into 2-oxazolines by the reaction with toluene-sulfonyl chloride (TsCl) in pyridine or with SOCl₂ in chloroform with subsequent treatment with saturated aqueous NaHCO₃. The reaction of dehydroabietic acid amide containing a monoethanolamine fragment with TsCl in pyridine was found to give the corresponding chloride in 60% yield instead of 2-oxazoline.