Photophysical and photochemical behavior of intramolecular styrene-amine exciplexes

Abstract

The photophysical and photochemical behavior of a series of secondary and tertiary w-(@tyryl)aminoalkanes with one to five methylenes separating the styryl and amino groups has been investigated and compared to the intermolecular reactions of 1 -phenylpropene with secondary and tertiary amines. The tertiary styrylamines form fluorescent intramolecular exciplexes, but fail to undergo intramolecular addition reactions. Both the rate constant for exciplex formation and the stability of the exciplex are dependent upon the length of the polymethylene chain connecting the chromophores. The failure of the tertiary amine exciplexes to undergo intramolecular addition is attributed to an unfavorable exciplex geometry for a-C-H transfer to the styrene double bond. While the secondary styrylamines do not form fluorescent exciplexes, the dependence of the styrene singlet lifetime upon the polymethylene chain length is similar to that for the tertiary styrylamines. Intramolecular N-H addition to the styrene double bond results in the formation of two regioisomeric (a-phenyl and a-benzyl) cyclic amines of different ring size. The regioisomer of larger ring size is favored except in the case in which four methylenes separate the chromophores. The effects of polymethylene chain length, solvent polarity, temperature, and the bulk of the N-alkyl group upon product yields and ratios are discussed in terms of a mechanism involving singlet exciplex and biradical intermediates.

On Thiol‐Ene Radical Coupling Reaction when Synthesis of ABCL2Type Heteroarm Star Copolymer Containing PDPA Arm

“…On the one hand, some amines could take in reaction in photoinitiated radical systems. [43,44] On the other hand, the tertiary amine moieties of the PDPA block creates alkaline environment, which led the thiol groups to produce thiolate anions. The formation of thiolates prevented thiol groups to be translated into thiyl radials.…”

Fluoxetine scaffold to design tandem molecular antioxidants and green catalysts

“…Such scaffold is found in many drugs like unarizine (calcium antagonist) and naine (antifungal). It must be noted that other strategies for the synthesis of allylamines were previously reported in the literature, such as the preparation from alcohols and amines through alkoxyphosphonium salts, 46 the reduction of secondary amides followed by N-methylation 47 or the reduction of propargylamines. 48 Nevertheless, the cited methods require hazardous and expensive reactants, harsh experimental conditions (temperature and pressure) and do not guarantee stereoselectivity.…”

A Multiphoton Single-Electron Reduction of Olefins via Tandem Photoredox Catalysis

“…Analysis of the crude reaction mixture revealed that yield was diminished by the formation of an a-amino adduct 3 (see SI, Table S1 for details), likely promoted by electrostatic interaction between the radical cation of DIPEA and the radical anion of the olefin 1. 18 Consequently, formic acid was added to the reaction mixture, to convert DIPEA into its formate salt and thus prevent formation of aamino radicals. 19 Pleasingly, addition of a slight excess of formic acid relative to DIPEA improved the yield to 82%, with no traces of the a-amino adducts detected in the 1 H NMR spectrum of the crude reaction mixture (Table 1, entry 6).…”