Photochemical generation and characterization of the 5-endo-10,11-dihydrodibenzoazepine nitrenium ion

Abstract

A photochemical precursor to the 5-endo-10,11-dihydroazepine nitrenium ion (1) was synthesized and used to characterize the intermediate by laser flash photolysis and stable product analysis. In addition, DFT calculations were carried out on the nitrenium ion. These results were compared with earlier studies on the diphenylnitrenium ion in order to ascertain the effect of the 2 carbon bridge on the reactions and properties of 1. It is shown that the geometric constraints provided by the bridging group (a) destabilize the triplet state of 1 relative to the singlet state (b) substantially increase the lifetime of 1 relative to Ph 2 N + by inhibiting the unimolecular cyclization pathway possible in the latter and (c) modestly increases the barrier for nucleophilic addition to the ring carbons.

Addition, Elimination, and Rearrangement Reactions of Cyclopropyl-Substituted Nitrenium Ions: A Computational and Experimental Investigation

“…The oil was then purified via column chromatography (30:1 Hexanes: Ethyl Acetate) to yield a yellow solid 34 (1.9189g, 81.7%). 1 30 The nitrosamine was synthesized following a known literature procedure. Amine 34 (1eq, 5.30 mmol, 1.11g), was added to a 100 mL round bottom flask equipped with a stir bar and dissolved in 25 mL of dimethylformamide.…”

“…kcal/mol higher in energy. [24][25][26][27][28][29][30] Conjugation with the aromatic ring results in significant positive charge delocalization onto the ring carbons. Indeed, nucleophiles tend to add to the aryl ring carbons in preference to the nitrogen.…”

Rearrangement, Elimination, and Ring-Opening Reactions of Cyclopropyl-Substituted Nitrenium Ions: A Computational and Experimental Investigation

“…1 N-([1,1′-Biphenyl]-4-yl)-N-cyclopropylnitrous Amide (35). 30 The nitrosamine was synthesized by following a literature procedure. Amine 34 (1 equiv, 5.30 mmol, 1.11 g) was added to a 100 mL round-bottom flask equipped with a stir bar and dissolved in 25 mL of dimethylformamide.…”

“…For example, arylnitrenium ions (i.e., PhNH + and its simple derivatives) are generally ground-state singlets having triplet states that are ca. 10–25 kcal/mol higher in energy. − Conjugation with the aromatic ring results in significant positive charge delocalization on the ring carbons. Indeed, nucleophiles tend to add to the aryl ring carbons in preference to the nitrogen.…”