The free-radical phenylation of isoquinolinium cation

Free-radical phenylation of isoquinolinium cation has been effected by photolysis of phenylthalliurn(III)di(trifluoroacetate) in a trifluoroacetic acid solution of isoquinoline. Analysis (g.l.c. and h.p.l.c.) of the isomeric phenylisoquinoline mixture showed that the dominant product (81.1 %) was 1-phenylisoquinoline, in accordance with two published theoretical predictions.

The Relative Reactivities of the Seven Nuclear Positions of Isoquinoline to Free-Radical Phenylation

Free-radical phenylation of isoquinoline has been effected both by photolysis of phenylthallium(III) di(trifluoroacetate) and by the action of pentyl nitrite on aniline. Analysis of the isomeric phenyl isoquinoline mixture by g.l.c. and h.p.l.c. established the reactivity order in the isoquinoline nucleus to be 1 > 5 > 8 > 4 > 3,6,7. This experimental order is compared with the eight published theoretical predictions, none of which is correct.

REACTIONS OF PHENYL-SUBSTITUTED HETEROCYCLIC COMPOUNDS: III. FREE-RADICAL PHENYLATION OF 1-PHENYLPYRAZOLE

Phenyl radicals furnished by benzoyl peroxide attack both rings of 1-phenylpyrazole, and the orientation of substitution has been examined using gas–liquid partition chromatography.Substitution occurs at all positions of the phenyl ring, although predominantly at the ortho positions, while attack in the pyrazole ring is confined to the 3-position. The results are in agreement with the suggestion that the free valence at a given position is a major factor in determining the orientation of free-radical phenylation of 1-phenylpyrazole, but in conflict with predictions from resonance theory.