Behaviour of delta^2-dihydropyran over hot alumina
Manolopoulos, Triantaphyllos Philip
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Earlier work has shown that alumina at 350° acts on tetrahydrofurfuryl alcohol labeled at its external methylene group with carbon-14, as well as on dihydropyran ([delta^2]-dihydropyran) labeled at its 6 position with carbon-14 to produce an equimolecular mixture of dihydropyran2-C14 and dihydropyran-6-C14. The present work inquires into the possibility of oxygen and of hydrogen exchange in dihydropyran in contact with alumina under the same conditions. Dihydropyran-O18 was synthesized for use in oxygen exchange experiments. Tetrahydrofurfuryl chloride, prepared from the correspondingalcohol with thionyl chloride and pyridine, was treated with sodium to give 4-penten-1-ol. This alcohol was converted to 1-bromo-4-pentene with phosphorus tribromide in pyridine. Reaction of the Grignard derivative of the bromo compound with formaldehyde-O18 gave 5-hexen-1-o1-O18s · The labeled formaldehyde was obtained by pyrolyzing labeled paraformaldehyde, which in turn was prepared from ordinary paraformaldehyde by depolymerization to formaldehyde, exchange of oxygen with water-O18, and repolymerization. A mixture of 5-hexen-1-o1-O18 and 5-hexen-1-ol-1-C14 was ozonized and the product dehydrated to give dihydropyran labeled with oxygen-18 and (at position 6) with carbon-14 [TRUNCATED]
Thesis (Ph.D.)--Boston University.