Photoinduced Electron-Transfer Degenerate Cope Rearrangement of 2,5-Diaryl-1,5-hexadienes:  A Cation-Radical Cyclization−Diradical Cleavage Mechanism

Ikeda, Hiroshi; Minegishi, T.; Abe, Hideyuki; Konno, Akinori; Goodman, Joshua L.; Miyashi, Tsutomu

doi:10.1021/ja971910s

Cited by 41 publications

(17 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Alkene oxidation by PET/redox mediation has also been leveraged for the rearrangement of polyunsaturated compounds such as aza-1,4-dienes , and 1,5-hexadienes, as well as tautomerization of styrenes, nucleophilic addition to 1,3-dienes, and the valence isomerization of norbornadiene . Among the most synthetically powerful transformations in this class are the radical cation cascades developed by Warzecha, Demuth, and Görner (Scheme ).…”

Section: Photoinduced Electron Transfermentioning

confidence: 99%

Dual Catalysis Strategies in Photochemical Synthesis

2016

View full text Add to dashboard Cite

The interaction between an electronically excited photocatalyst and an organic molecule can result in the genertion of a diverse array of reactive intermediates that can be manipulated in a variety of ways to result in synthetically useful bond constructions. This Review summarizes dual-catalyst strategies that have been applied to synthetic photochemistry. Mechanistically distinct modes of photocatalysis are discussed, including photoinduced electron transfer, hydrogen atom transfer, and energy transfer. We focus upon the cooperative interactions of photocatalysts with redox mediators, Lewis and Brønsted acids, organocatalysts, enzymes, and transition metal complexes.

show abstract

Section: Photoinduced Electron Transfermentioning

confidence: 99%

Dual Catalysis Strategies in Photochemical Synthesis

2016

View full text Add to dashboard Cite

show abstract

“…Thus, matrix isolated 1,5-hexadiene radical cation generated by pulse radiolysis spontaneously cyclizes to the cyclohexane-1,4-diyl radical cation. 25,26 Consequently, Ikeda et al 27 have used photoinduced electron transfer to afford the cyclization of a phenyl-substituted hexadiene derivative.Recently reported electronic structure calculations predict that, in select cases, single electron reduction can also catalyze the Cope rearrangement because the electron affinity of the openshell transition state is much greater than that of the closedshell hexadiene (Figure 1). 28 For example, cyclization of the radical anion of 2,5-dicyano-1,5-hexadiene (2a, eq 1) to form the corresponding cyclohexane-1,4-diyl radical anion 2b is calculated to be exothermic by 16.2 kcal/mol (B3LYP/6-31+G*).…”

mentioning

confidence: 99%

An Electron-Catalyzed Cope Cyclization. The Structure of the 2,5-Dicyano-1,5-hexadiene Radical Anion in the Gas Phase

Hammad

Wenthold

2003

J. Am. Chem. Soc.

View full text Add to dashboard Cite

The radical anion of 2,5-dicyano-1,5-hexadiene is shown to undergo Cope cyclization in a flowing afterglow-triple quadrupole apparatus. The cyclic structure of the 2,5-dicyano-1,5-hexadiene radical anion was established by using chemical reactivity. The ion reacts with CO2 and CS2 by addition, whereas the radical anions of closed-shell molecules such as fumaronitrile do not react with these reagents. The ion exhibits reactivity characteristic of a distonic ion in that it sequentially adds CO2 and NO or NO2. It reacts with NO by forming a product at m/z 135 corresponding to addition followed by loss of HCN. The reactivity and CID spectrum of the product ion at m/z 135 agrees with that of oximate ion, which requires a cyclic precursor ion. Attempts to generate radical anions of acrylonitrile and 2,6-dicyano-1,6-heptadiene were unsuccessful, providing additional evidence against a linear structure as a stable structure for 2,5-dicyano-1,5-hexadiene radical anion. The cyclization of the radical anion of the 2,5-dicyano-1,5-hexadiene is the first example of an electron-catalyzed Cope cyclization.

show abstract

“…In these systems, carbons at the reaction centers do not satisfy the octet rule. Importantly, the latter situation exists with ring‐opening reactions of radical cations 1 .+ (Figure ) and, thus, the rates of these processes should be entropy controlled …”

Section: Methodsmentioning

confidence: 99%

“…Importantly, the latter situation exists with ring-opening reactions of radical cations 1 * + (Figure 3) and, thus, the rates of these processes should be entropy controlled. [36][37][38][39][40][41] The calculated activation parameters ΔH � , ΔS � , and ΔG � at 298 and 130 K in the gas phase are listed in Table 1. The order of ΔS � is turned out to be the reverse of that of ΔH � (and of course, with that of E a ).…”

Section: Rates Of Ring Opening Of Radical Cation Intermediates Governmentioning

confidence: 99%

Rates of Ring Opening of Radical Cation Intermediates Govern Differences in Thermoluminescence between 1‐ and 2‐Naphthyl‐Substituted Methylenecyclopropanes

et al. 2019

Self Cite

View full text Add to dashboard Cite

In this study, we observed that methylenecyclopropane 1 c, possessing geminal phenyl and 1‐naphthyl groups at C‐2 of the three membered ring, emits green thermoluminescence (TL) in a low temperature matrix, associated with two sets of bands in the 480–600 and 600–700 nm regions. The bands are assigned to phosphorescence from 31 c* and triplet‐triplet (T−T) fluorescence (FL) from the corresponding trimethylenemethane biradical 32 c..*, respectively. In contrast, as previously reported, the analogous 2‐naphthyl derivative 1 b emits red TL associated with two bands in the 350–450 and 600–700 nm regions, which are assigned to FL from 11 b* and T−T FL from 32 b..*. The results of spectroscopic studies and density functional theory calculations show that the observed dissimilarity in the TL properties of 1 b and 1 c is a consequence of differences in the rate of methylenecyclopropane ring opening of 1 b.+ and 1 c.+ associated with stereoelectronic effects of the naphthyl groups.

show abstract

Photoinduced Electron-Transfer Degenerate Cope Rearrangement of 2,5-Diaryl-1,5-hexadienes: A Cation-Radical Cyclization−Diradical Cleavage Mechanism

Cited by 41 publications

References 54 publications

Dual Catalysis Strategies in Photochemical Synthesis

Dual Catalysis Strategies in Photochemical Synthesis

An Electron-Catalyzed Cope Cyclization. The Structure of the 2,5-Dicyano-1,5-hexadiene Radical Anion in the Gas Phase

Rates of Ring Opening of Radical Cation Intermediates Govern Differences in Thermoluminescence between 1‐ and 2‐Naphthyl‐Substituted Methylenecyclopropanes

Contact Info

Product

Resources

About