Journal of Synthetic Organic Chemistry, Japan

Hydrogenation of 3-(2-furyl)acrolein with nickel on kieselguhr catalyst or Raney nickel in water medium gives 1, 6-dioxaspiro [4, 4] nonane and 1, 4, 7-heptantriol as the by-products, by the partial cyclization of side chain and the opening of furan ring. Raney nickel catalyst at 60-80°c. under the pressure of 30-50kg/cm² caused hydrogenation of side chain easily but the hydrogenation of furan ring was difficult. In order to obtain 3-(2-tetrahydrofuryl)propanol with good yield, it was necessary to carry the reaction at 140-150°c under the initial pressure of hydrogen of 100-130 kg/cm2 in the presence of primary alcohols (nearly absolute) of above 3.5 times by volume. Raney nickel of powdered or granular form showedd a strong activity at the initial period but it was unsuitable from the results of its, life-tests. The molded nickel on celite catalyst was found to be most suitable.

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The reactions of 3-(2-tetrahydrofuryl) propanol (THFPA) and 3-(2-tetrahydrofuryl) propyl bromide (THFPB) with hydrogen bromide were investigated to obtain 1, 7-dibromoheptene-3 (1, 7-DBH) with good yield. The results indicated that thisring-opening reaction was an ionic reaction and the reaction products were varied depending on the reaction temperature, molar ratio of hydrogen bromide and gaseous state of hydrogen bromide or aqueous state. Reaction of THFPA with 1 mole aqueous solution (48%) of hydrogen bromide for 3 hrs at 30-40°c yielded 91% of THFPB. Reaction of 1 mole hydrogen bromide and THFPB at 30-40°c gave a mixture of 1, 7-dibromoheptan-4-ol (1, 7-DBH 4O) and 1, 4-dibromoheptan-7-ol (1, 4-DBH 7O). Heating of this mixture in a vacuum(25-30 mm Hg) at 100°c gave violent evolution of hydrogen bromide and gave original THFPB. On the other hand, heating of a mixture of 1, 7-DBH 4O and 1, 4-DBH 7O in 60% sulfuric acid at 115-120°c caused a thermal dehydration and yielded a mixture containing 46% THFPB, 38% 1, 7-DBH and 26% 1, 4, 7-tribromoheptane (1, 4, 7-TBH). The reaction of a mixture of THFPB and acetic anhydride with 1 mole hydrogen bromide at 30-35°c gave 88% dibromoacetoxyheptane; heating this at 230-240°c caused the liberation of acetic acid and yielded 66% 1, 7-DBH.v Passing of 2 mole hydrogen bromide into THFPB at 90-100°c gave 93%1, 4, 7-TBH, but heating of THFPB with aqueous solution of hydrogen bromide (48%) of 2.5-4 moles at 120-125°c yielded a mixture of 31-32% 1, 7-DBH and 58-60% 1, 4, 7-TBH. Although 1, 4, 7-TBH is stable at a temperature below 130°c, heating of 1, 4, 7-TBH at 150-200°c without catalyst caused a selective dehydrobromination of secondary bromine and gave above 97% of 1, 7-DBH. This formation reaction of 1, 7-DBH is proceeded according to the first-order reaction and its activation energy is 13.6 kcal/mol. However, dehydrobromination reaction of 1, 4, 7-TBH by alkali showed no selectivity between the primary and secondary bromine and yielded about 30% of 1, 7-DBH. In the case of using THFPA as a starting material, above 3 moles hydrogen bromide and above 2 moles in case of THFPB was heated at 120-125°c to obtain a mixture of 1, 7-DBH and 1, 4, 7-TBH and this produts was heasted in a vacuum (50-60 mm Hg) at 160-170°c to obtain from 92% to 97% 1, 7-DBH THFPB. The reaction mechanism of formation of 1, 7-DBH and 1, 4, 7-TBH has been discussed with these results. Furthermore of 1, 7-dicyanoheptene-3, 3-heptene-1, 7-dicarboxylic acid and azelaic acid were synthesised from 1, 7-DBH.

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