Alkynic fatty acids: ω-Arylation, methoxycarbonylation to α,β-unsaturated esters, cyclotrimerization to pyridines and 2-pyridones

Dehydrogenation of double to triple bonds by bromination/dehydrobromination and triple bond isomerization by the alkyne zipper reaction provide a short and facile access to internal and terminal alkynic fatty acids. Thereby methyl 10-undecynoate, methyl 9-octadecynoate, methyl 17-octadecynoate and derivatives have been prepared from the corresponding alkenic fatty acids. Their conversions are reported: The hydrogen in the terminal alkynic fatty compounds is substituted in a omega-carboxylation and a palladium(0)-catalysed omega-arylation. With carbon monoxide/methanol internal alpha,beta-unsaturated monoesters and terminal unsaturated diesters are obtained under mild conditions by palladium(II)-catalysis. Furthermore dimer fatty acids with a pyridine and a 2-pyridone core are prepared by cyclotrimerizations of alkynic fatty compounds with alkylnitriles and N-phenylisocyanate.