ABSTRACT
2-Substituted indoles (5a,b and 7) and fused indoles (9a-c, 11a,b, and 12) have been obtained by the S(RN)1 mechanism from photostimulated reactions of o-iodoaniline (1) and 1-halo-2-naphthalen-2-ylamines (3a,b) with enolate ions of acyclic (acetophenone (6), 2- (4a) and 4-acetylpyridine (4b)) and cyclic ketones (1- (8a) and 2-indanone (10a), 1- (8b) and 2-tetralone (10b) and 1-benzosuberone (8c)) in DMSO and liquid ammonia as solvents. The carbanions derived from 4a,b, 8a, and 10b are novel nucleophiles that form new C-C bonds by the S(RN)1 mechanism.
ABSTRACT
The reactions of 1,3-dihaloadamantanes with various carbanionic nucleophiles were studied. Potassium enolates of acetophenone (2) and pinacolone (10b) and the anion of nitromethane (10a) reacted with 1,3-diiodoadamantane (1a) in DMSO under photostimulation by a free radical chain process to form a 1-iodo monosubstitution product as an intermediate, which undergoes concerted fragmentation to form derivatives of 7-methylidenebicyclo[3.3.1]nonene (3 and 11). This reaction does not occur in the dark at 25 degrees C, and the photostimulated reaction is partially inhibited by p-dinitrobenzene. 1,3-Dibromoadamantane (1b) and 1-bromo-3-chloroadamantane (1c) also reacted under irradiation with 2, although more sluggish than 1a, also giving the 7-methylidenebicyclo[3.3.1]nonene derivative 3. When a nucleophile was used without acidic hydrogens in the alpha-position, such as the enolate ion of isobutyrophenone (16), in order to inhibit the ring opening of adamantane, it reacted under irradiation with 1a to give the products adamantane, 1-iodoadamantane, monosubstituted 17, 1-iodo-monosubstituted 19, and disubstituted 20. Their distribution depended on the experimental conditions. In these reactions, 1-iodoadamantane and 19 were intermediates. For reactions involving the radical anion intermediate of the 1-iodo monosubstitution product, the intermolecular ET to the substrate was observed to be much faster than intramolecular ET to the C-I bond.
