In all cases, the double bond migration is easy to recognize as the signal for the two aldehydic protons separate well in the 1 H NMR of the mixtures of isomers. The aldehydic proton of the desired β,γ-unsaturated compounds appears at δ 9.64–9.67 as a broad triplet and the aldehydic proton of the α,β-unsaturated isomers appears as expected upfield at δ 9.52–9.55 as a doublet. The ratio of these two protons gives an accurate indication of the isomerization ...