Reactions of 2-Iodo- and 1,2-Dihaloadamantanes with Carbanions in DMSO by the S_RN1 Mechanism

Abstract

The reaction of 2-iodoadamantane (1) with the potassium enolate of acetophenone (2) did not occur in the dark but succeeded under irradiation or in the presence of FeBr2 to give the substitution product 3 in 62% and 88% yields, respectively. The photostimulated reaction was inhibited by p-dinitrobenzene (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 presence of acetone enolate ion (entrainment reaction) to yield 88% of the substitution product 2-adamantylnitromethane (5). The photostimulated reaction of 1 with anthrone (6), 2-naphthyl methyl ketone (9), and N-acetylthiomorpholine (11) anions afforded the substitution compounds 7 (37%), 10 (32%), and 12 (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 α-(1-chloro-2-adamantyl)acetophenone (14). Under longer irradiation time (3 h), the same yield of 14 (52%) was obtained 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-iodoadamantane (18) did not react with 2 in the dark (2 h), but the photostimulated reaction yielded the monosubstitution product α-(2-chloro-1-adamantyl)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 dark reaction of 1,2-diiodoadamantane (20) with 4 in the presence of acetone enolate ion to afford the iodomonosubstitution compound 21 (40%) and the disubstitution product 22 (13%). The photostimulated reaction (25 min) gave 21 (48%) and 22 (41%). On the other hand, after 3 h of irradiation, only traces of 21 could be detected (<5%) and the product distribution consisted mainly of 22. The iodomonosubstitution product 21 is an intermediate in these reactions.

Strategies in Synthetic Radical Organic Chemistry. Recent Advances on Cyclization and SRN1 Reactions

“…88). After 5 minirradiation, only 107 is formed, but in 3 hr-irradiation, 107 and 108 are formed in 52% and 45% yields, respectively [177].…”

“…The photostimulated reaction of 2-iodoadamantane (2-AdI) with carbanions derived from acetophenone, 2-naphthyl methyl ketone, N-acetylmorpholine, and anthrone afford substitution products in moderate yields (62%, 32%, 32%, and 37%, respectively) [177]. The reaction with -CH 2 COPh anion induced by FeBr 2 , renders 88% yield of substitution.…”

“…The reaction with -CH 2 COPh anion induced by FeBr 2 , renders 88% yield of substitution. Nitromethane anion is unreactive under irradiation, but in the presence of -CH 2 COMe anion, as entrainment reagent, 88% yield of substitution is furnished [177].…”

“…The photostimulated reaction of 1,2-diiodoadamantane with -CH 2 NO 2 anions (induced by -CH 2 COMe anions) affords the disubstituted product in 68% yield [177].…”

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

“…[30] 2) Quenching of the reaction by trace amounts of oxidising agents (e.g., p-dinitrobenzene, CuCl 2 ) or radical traps (e.g., di-tert-butyl nitroxide). [26,[31][32][33][34] 3) Entrainment of the reaction: [25,[35][36][37] for example, the anion of MeNO 2 does not react with 1-iodoadamantane under irradiation, but excellent yields of 1-adamantylnitromethane are obtained in the photostimulated reaction in Scheme 1. Extending this scheme to the formation of a Grignard reagent, the role of donor would be played by the active sites of the magnesium metallic surface (see text).…”