Electron-Transfer Nucleophilic Substitution Reactions on Neopentyl- and Phenyl-Substituted Alkyl Chlorides. Effect of the Bridge Length on the Intramolecular Electron-Transfer Catalysis

Abstract

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.

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

“…While for iodides evidence for a radical single electron transfer process as the major pathway was found, the corresponding bromides and chlorides seemed to prefer an S N 2 mechanism. Rossi et al [ 21 ] showed that substitution products can be obtained in good yields from neopentyl chloride derivatives and sodium diphenylphosphide in liquid ammonia by an S NR 2 reaction induced by UV irradiation. Huttner and co-workers [ 22 ] on the other hand achieved high yields in nucleophilic substitutions of diarylphosphines with MeC(CH 2 Cl) 3 in DMSO using aqueous KOH as base at elevated temperature but without irradiation.…”

Reaction of 1-Substituted 2,2-Dimethyl-3-phenylpropane with t-BuOK in DMSO. An Unexpected Formation of a Cyclopropane Ring

“…Materials. 1-Iodo-2,2-dimethyl-3-phenylpropane 12 (1) and 1-chloro-2,2-dimethyl-3-phenylpropane 13 (11) were synthesized by reaction of the corresponding tosylate with KI or LiCl in DMF. The tosylate (12) and the benzenesulfonate (13) were prepared by standard procedures.…”

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

“…Chlorine derivatives such as, neopentyl [191], neophyl [192], and 2,2-dimethyl-3-phenyl-1-propyl [192], can also be substituted by Ph 2 P -ions. Reactions in which the substituted phosphine oxides (70%, 74% and 49% yields, respectively) are obtained upon oxidation.…”