Reactions of 2-iodo- and 1,2-dihaloadamantanes with carbanions in DMSO by the S(RN)1 mechanism

The reaction of 2-iodoadamantane (1) with the potassium enolate of acetophe none (2) did not occur in the dark but succeeded under irradiation or in th e presence of FeBr2 to give the substitution product 3 in 62% and 88% yield s, respectively. The photostimulated reaction was inhibited by p-dinitroben zene (p-DNB). There was no reaction of 1 with the anion of nitromethane (4) in the dark or under irradiation. However, 4 reacted with 1 in the presenc e of acetone enolate ion (entrainment reaction) to yield 88% of the substit ution product 2-adamantylnitromethane (5). The photostimulated reaction of 1 with anthrone (6), 2-naphthyl methyl ketone (9), and N-acetylthiomorpholi ne (11) anions afforded the substitution compounds 7 (37%), 10 (32%), and 1 2 (20%), respectively. There was no reaction of 1-chloro-2-iodoadamantane ( 13) with 2 in the dark (2 h), but under irradiation (5 min) it yielded 52% of the monosubstitution product alpha-(1-chloro-2-adamantyl)acetophenone (1 4). Under longer irradiation time (3 h), the same yield of 14 (52%) was obt ained but the disubstitution product 15 was formed in 45% yield. Product 15 was also formed in the photostimulated reaction of 14 with 2. 2-Chloro-1-i odoadamantane (18) did not read with 2 in the dark (2 h), but the photostim ulated reaction yielded the monosubstitution product alpha-(2-chloro-1-lada mantyl)acetophenone (19) in 53% and 15 in 4% yield. Products 14 and 19 are intermediates in the formation of 15 in these reactions. There was a slow d ark reaction of 1,2-diiodoadamantane (20) with 4 in the presence of acetone enolate ion to afford the iodomonosubstitution compound 21 (40%) and the d isubstitution product 22 (13%). The photostimulated reaction (25 min) gave 21 (48%) and 22 (41%). On the other hand, after 3 h of irradiation, only tr aces of 21 could be detected (<5%) and the product distribution consisted m ainly of 22. The iodomonosubstitution product 21 is an intermediate in thes e reactions.