Reactions of dispiro[2.0.2.2]oct-7-ene. Electrophilic and free radical additions

Dispiro2.0.2.2]oct-7-ene 1 was synthesized by debrominatioa of cis- and trans-7,8-dibromodispiro2.0.2.2]octane 3a with LAH and by dechlorination of cis- and trans-7,8-dichlorodispiro2.0.2.2]octane 3b with magnesium. Stepwise electrophilic additions to 1 of HBr, HI, Br₂ and Cl₂ were studied. The major products (and yields) from these reactions were: 7-bromodispiro2.0.2.2]octane 2a (43%), 4-iodo-4,5-ethanospiro2,3]hexane 4b (ca. 50%); trans-3a (40%); and cis-3b (20%). Free-radical addition of hydrogen bromide to 1 gave an 80% yield of 7-bromodispiro2.0.2.2]octane 2a. At ?10°, hydroboration-oxidation of 1 was found to give mainly 7-hydroxydispiro2.0.2.2]octane 2a in ca. 90% yield; at 25°, near equal amounts of 2c and 4-(2-hydroxyethyl) spiro2.3]hex-4-ene 14 were obtained.