Thermolysis of 1-homcadamantyl hypoicdite followed by intramolecular cyclization yields 74% of the hitherto unknown lo-homcprctoadamantan-4-one;
the hypoicdite thermolysis-cyclizatien sequence appears to be an excellent method for the preparation of adamantanoid ketones. ~3 -Scission of tertiary polycyclic hypohalites attracted our attention as a potentially general route to adamantanoid ketones. While thermolysis and photolysis of long chain aliphatic hypohalites yield mainly d-haloalcohols, ' short chain aliphatic and cyclic hypohalites give substantial amounts of /J-scission products -ketones and halides. 192 This has scarcely been used in synthetic chemistry. I,2 4-Protoadamantanone was obtained in 35% yield by thermolysis of I-adamantyl hypohalite followed by cyclization of the resulting haloketone. 3 In spite of the low and erratic yield, this reaction sequence has been the most convenient entry to the protoadamantane system.
Recently we found4 that the yield of 4-protoadamantanone (7 98% pure by GLC) could be increased to a steady 65-75% if the hypoiodite reaction of 1-adamantanol was carried out in a dilute benzene solution at 70' C. 5
We now report the thermolysis of 1-homoadamantyl hypoiodite (Ib) and the intramolecular cyclization of the resulting iodoketone. Contrary to 1-adamantyl hypoiodite, only two of the three /3-C, C-bonds in 1. are equivalent @ # b) and, consequently, two isomeric iodoketones, 2 and 3_, could be formed by /J-scission. Intramolecular base promoted C-alkylation of 2 and 2 could be expected 3,8 to produce homoprotoadamantane ketones 2 and 5, and 2, respectively.
1-Homoadamantyl hypoiodite (Ib) was prepared in situ from 1-homoadamantanol" Ila) by the modified hypoiodite reaction.