Three-Electron S_N2 Reactions of Arylcyclopropane Cation Radicals. 1. Mechanism¹

Abstract

The mechanism of photosensitized nucleophilic substitution reactions on arylcyclopropanes was investigated. Stereochemical experiments with methanol, water, and cyanide as nucleophiles showed that the reactions occurred stereospecifically with complete inversion of configuration at the carbon atom undergoing substitution. Independent generation of the arylcyclopropane cation radicals by nanosecond transient methods showed that they reacted rapidly with nucleophiles with kinetics that were first-order in both the cation radical and the nucleophiles. Through a combination of transient kinetics and steady-state Stern−Volmer quenching experiments, the reaction of the phenylcyclopropane cation radical with methanol was kinetically correlated with the formation of the substitution product. The reaction of phenylcyclopropane cation radical with a series of alcohols as nucleophiles showed small steric effects.

The first calibration of an aminiumyl radical ion clock: why N-cyclopropylanilines may be poor mechanistic probes for single electron transfer

“…+ ) undergoes clean, first-order decay, consistent with a unimolecular rearrangement attributable to (1) cyclopropane ring opening (Scheme 1, path a). The fact that the decay is zero order in methanol effectively rules out the nucleophile-assisted pathway for ring opening, analogous to that documented for cyclopropylarene radical cations 20,21 (Scheme 1, path c), at least for methanol as a nucleophile.…”

Electrochemical mass spectrometric studies on 1‐cyclopropyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine

“…Alternatively, 3 .+ could undergo ring opening via nucleophilic attack by a solvent molecule to yield 16 . that would undergo a second one‐electron oxidation coupled with hydration to give 14 9…”

Arylcyclopropanes: Properties, Synthesis and Use in Medicinal Chemistry

“…[145][146][147][148][149][150][151] It is the combination of these features and the conjugative effects described above that have attracted medicinal chemists to this class of molecules. On one hand, the arylcyclopropane moiety can make van der Waal's contacts just as alkyl arenes similar in size and with similar electrostatic surface potentials do.…”