Substitution reactions which proceed via radical anion intermediates. 29. Electron-transfer substitution reactions: p-nitrocumyl system

Abstract

Fade substitution reactions at the tertiary carbon of p-nitrocumyl chloride and a,p-dinitrocumene are described. These reactions occur with a wide range of organic and inorganic nucleophiles and are noteworthy for providing novel and powerful means of synthesis; they occur readily under mild conditions, give excellent yields of pure products, and, in contrast to SN2 displacements, are rather insensitive to steric hindrance. They are, therefore, especially valuable for the preparation of highly branched compounds. The view that these are electron-transfer chain processes derives from inhibition studies and, also, from the fact that these reactions are induced by one-electron-transfer agents. (1) Substitution Reactions Which Proceed via Radical Anion Intermediates. 29. Part 2 8 Kornblum, N.; Kelly, W. J.; Kestner, M. M. J. Org. Chem. 1985,50, 4720. This paper is based on the doctoral dissertations of the 12 junior authors. Reference to these theses is made by employing the initials of the author and the date of the thesis. Preliminary communications have appeared in:

“Thermal” SRN1 Reactions: How Do They Work? Novel Evidence that the Driving Force Controls the Transition between Stepwise and Concerted Mechanisms in Dissociative Electron Transfers

“…Reaction of 4-Nitrocumyl Chloride with Other Nucleophiles. The reactions of the same substrate, 4-nitrocumyl chloride, with a few other nucleophiles have been previously investigated, and the half-reaction times can be estimated from reported data . Although all of the pertinent rate constants are not as precisely known as those with the 2-nitropropanate ion, we may attempt to see whether the same mechanistic conclusion is valid for these nucleophiles, too.…”

New Insights into an Old Problem. Fluorescence Quenching of Sterically-Graded Pyrenes by Tertiary Aliphatic Amines

“…Tertiary amines and trans -decalin used in quenching studies were distilled by fractional distillation using a low pressure (0.5–10 Torr) or house vacuum (250 Torr) prior to use, and the purity was ≥99% as indicated by gas chromatography. 1,4-Diazabicyclo[2.2.2]­octane was recrystallized twice from ethanol (mp 157–158 °C; Lit: 155–157 °C). trans -Decahydroquinoline hydrochloride salt was made in and precipitated from diethyl ether.…”

Aberrant SRN1 Reaction of 4-Aminophenol with α,p-Dinitrocumene: EPR Observation of Intermediates

“…Interest in the scope of electron transfer induced nucleophilic substitutions and in the factors controlling them has intensified recently due to imaginative exploitations of inter- and intramolecular versions of this reaction in new synthetic procedures. 1a-f The substitution of NO 2 in α, p -dinitrocumene [2-nitro-2-(4-nitrophenyl)propane 1 ] by sundry nucleophiles is regarded as a representative S RN 1 process. , Kornblum and co-workers studied the reaction of 1 with carbon-centered nucleophiles, thiolate, CN - , N 3 - , amines, and 1-methyl-2-naphtholate anion some time ago. , According to the orthodox S RN 1 mechanism the process is initiated by electron transfer to 1 , followed by rapid and irreversible decomposition of the resulting radical anion 2 to give the 4-nitrocumyl radical ( 3 ) and nitrite ion. The key step is coupling of a nucleophile (ArO - ) with 3 to produce the radical anion of the substitution product ( 4 ).…”

“…1,2 Kornblum and co-workers studied the reaction of 1 with carbon-centered nucleophiles, thiolate, CN -, N 3 -, amines, and 1-methyl-2-naphtholate anion some time ago. 3,4 According to the orthodox S RN 1 mechanism the process is initiated by electron transfer to 1, followed by rapid and irreversible decomposition of the resulting radical anion 2 to give the 4-nitrocumyl radical (3) and nitrite ion. The key step is coupling of a nucleophile (ArO -) with 3 to produce the radical anion of the substitution product (4).…”