The nucleophilic substitution reaction of the chlorides RMe(2)CCH(2)Cl (R = Me, 4; Ph, 5a; PhCH(2), 5b) and their relative reactivities toward diphenyl phosphide ions were studied under irradiation in liquid ammonia. The relative reactivities determined were k(5a)()/k(4)() congruent with 9 and k(5b)()/k(4)() congruent with 0.85. These reactions are proposed to occur through the S(RN)1 mechanism. The higher reactivity of 5a is explained on the basis of its higher electron affinity due to the phenyl substitution and the efficient intramolecular electron transfer from this group to the C-Cl sigma bond (intra-ET catalysis). Although 5b also has a phenyl ring, its lower reactivity is ascribed to a decrease in the rate of the intra-ET by elongation of the bridge in one methylene unit. The relative reactivity of 5a versus 5b (k(5a)()/k(5b)() congruent with 6.4) is proposed to indicate the ratio of the intra-ET rates of the radical anions of both compounds. AM1 calculations performed on the system are in agreement with the experimental results.

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The photoinitiated reaction of 2-(4-halophenyl)-2-methyl-1-chloropropane 2a,b (halogen=Br, I, respectively) with the anions of pinacolone (3a) and acetophenone (3b) either in DMSO or in liquid ammonia are reported. In DMSO, the main reaction is the SRN1 nucleophilic substitution at the aromatic (Csp2-halogen) center with substitution or reduction at the aliphatic (Csp3-Cl) one. In liquid ammonia, the main reaction is substitution at the aromatic C-halogen site. This difference in product distribution is ascribed to modifications in the rate constant of Csp3-Cl dissociation of the radical anions proposed as intermediates in going from DMSO (rt) to liquid NH3 (-33 degrees C).

Synthesis of 2-Phenyl-1-(2-thienyl)-and 2-Aryl-1-(2-furyl)ethanones by the S RN 1 Mechanism. Relative Reactivities of Enolate Ions of Ketones.-The reaction of the enolate ions of furan (I) and thiophene (VIII) with different aryl halides is studied to determine their reactivity, the initiation conditions that favor the substitution reaction (photoinitiation and initiation by ferrous ion), and the possibility of increasing their synthetic scope. The relative reactivities of these enolates with respect to the enolate ions of acetophenone and 2-acetylnaphthalene are determined. -(BAUMGARTNER, M. T.; GALLEGO, M. H.; PIERINI, A. B.; J.