An investigation has been made of die reaction of butadiene dimers - 1
,3.7-octatriene and 2-methyl-1,4,6-heptatriene - with formaldehyde und
er conditions of the Prins reaction. It is shown that, depending on th
e nature of the catalyst (H2SO4, BF3.O(C2H5)2), the reaction of butadi
ene dimers with formaldehyde leads to a mixture of 1,3-dioxanes and di
hydropyrans or only to the latter.