Kinetics of Dialkylaminium Cation Radical Reactions: Radical Clocks, Solvent Effects, Acidity Constants, and Rate Constants for Reactions with Hydrogen Atom Donors

Horner, John H.; Martinez, Felix N.; Musa, Osama M.; Newcomb, Martin; Shahin, Haifa

doi:10.1021/ja00150a012

Cited by 84 publications

(64 citation statements)

References 8 publications

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“…The thiyl could accept an electron from the reduced state of the photocatalyst and the resulting thiolate could deprotonate the closed-shell ammonium adduct to provide the desired tertiary amine product and close the catalytic cycle. Aminiums are potent H-atom abstractors, and are known to react rapidly with aryl thiols containing much weaker S-H bonds (20). However, we recently demonstrated that aryl thiols can function effectively as H-atom donor catalysts in the presence of even more reactive amidyl and alkoxy radical abstractors (28, 29), likely due to mismatched polar effects that are well known to impact the rates of organic HATs (30).…”

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confidence: 99%

“…Specifically, the more electron-rich trisubstituted olefin in the terpene linalool could be aminated selectively in the presence of the terminal allylic alcohol (19). Similarly, geraniol derivatives bearing two sterically similar trisubstituted alkenes could be selectively aminated at the more electron-rich olefin distal to the allylic ester moiety (20). Cyclooctadiene was also a successful substrate for amination, providing 21 in 86% yield.…”

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confidence: 99%

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Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines

Musacchio

Lainhart

Zhang

et al. 2017

Science

311

209

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The intermolecular hydroamination of unactivated alkenes with simple dialkyl amines remains an unsolved problem in organic synthesis. Here we report a catalytic protocol for efficient additions of cyclic and acyclic secondary alkyl amines to a wide range of alkyl olefins with complete anti-Markovnikov regioselectivity. In this process, C–N bond formation proceeds through a key aminium radical cation intermediate that is generated via electron transfer between an excited state iridium photocatalyst and an amine substrate. These reactions are redox neutral, completely atom economical, exhibit broad functional group tolerance, and occur readily at room temperature under visible light irradiation. Certain tertiary amine products are formally endergonic relative to their constituent olefin and amine starting materials and thus are not accessible via direct coupling with conventional ground state catalysts.

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confidence: 99%

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confidence: 99%

Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines

Musacchio

Lainhart

Zhang

et al. 2017

Science

311

209

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“…[7] Ingold et al reported the rate constant for ring opening of the cyclobutyl-n-propylaminyl radical to be 1.2 10 5 s À1 at 25 8 8Cw hereas the rate constant was estimated to be greater than 10 7 s À1 at 25 8 8Cf or ring opening of the cyclopropyl-npropylaminyl radical (Scheme 1). [8] Thep roposed ring opening of the cyclobutylaniline radical cation was expected to be faster than the neutral aminyl radical, [9] which lent further credence to the proposed annulation reaction. Surprisingly,to the best of our knowledge,there have been no reports of using cyclobutylanilines in the tandem ring opening and annulation sequence to construct six-membered carbocycles.T his is in contrast to the increasing use of other types of cyclobutanes in the tandem sequence.…”

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confidence: 88%

The Cleavage of a CC Bond in Cyclobutylanilines by Visible‐Light Photoredox Catalysis: Development of a [4+2] Annulation Method

Wang

Zheng

2015

Angewandte Chemie

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Abstract:We report the first example of an intermolecular [4+ +2] annulation of cyclobutylanilines with alkynes enabled by visible-light photocatalysis.M onocyclic and bicyclic cyclobutylanilines successfully undergo the annulation with terminal and internal alkynes to generate aw ide variety of aminesubstituted cyclohexenes including new hydrindan and decalin derivatives with good to excellent diastereoselectivity.T he reaction is overall redox neutral with perfect atom economy.The release of ring strain has often been exploited as adriving force to promote the cleavage of typically unreactive bonds such as carbon-carbon bonds.[1] This strategy has been successfully applied to the ring opening of cyclopropanes, which leads to the wide use of cyclopropanes in organic synthesis.[2] We recently reported visible-light-promoted [3+ +2] annulation reactions of cyclopropylanilines with various p bonds.[3] In these reactions,t he cleavage of the cyclopropyl rings is promoted by photooxidation of the parent amine to the corresponding amine radical cation. Since the oxidation potentials of cyclopropylaniline and cyclobutylaniline were found to be similar, [4] we were intrigued by the possibility of using cyclobutylanilines in asimilar manner in the annulation reactions.W ewere further encouraged by the fact that cyclobutanes strain energy is almost identical to that of cyclopropane. [5,6] Still, the ring opening of cyclopropanes is generally much faster than that of cyclobutanes.Newcomb et al. reported that the rate constant for ring opening of ac yclobutylcarbinyl radical was 1.5 10 3 s À1 at 20 8 8Cc ompared to 710 7 s À1 at 20 8 8Cf or ring opening of ac yclopropylcarbinyl radical. [7] Ingold et al. reported the rate constant for ring opening of the cyclobutyl-n-propylaminyl radical to be 1.2 10 5 s À1 at 25 8 8Cw hereas the rate constant was estimated to be greater than 10 7 s À1 at 25 8 8Cf or ring opening of the cyclopropyl-npropylaminyl radical (Scheme 1). [8] Thep roposed ring opening of the cyclobutylaniline radical cation was expected to be faster than the neutral aminyl radical, [9] which lent further credence to the proposed annulation reaction. Surprisingly,to the best of our knowledge,there have been no reports of using cyclobutylanilines in the tandem ring opening and annulation sequence to construct six-membered carbocycles.T his is in contrast to the increasing use of other types of cyclobutanes in the tandem sequence.[10] Successful ring opening of these cyclobutanes usually relies on the decoration of the cyclobutyl ring with donor-acceptor [11] or ketone/hydroxy functionalities.[12] Herein we describe the successful development of the [4+ +2] annulation of cyclobutylanilines with alkynes by visiblelight photoredox catalysis,w hich greatly broadens the use of cyclobutanes as af our-carbon synthon in organic synthesis. We hope that this method will add to the growing pool of synthetic methods based on photocatalysis. [13] We chose 4-tert-butyl-N-cyclobutylaniline 1a and phenylacetylene 2a as the standard...

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“…Die Tr iebkraft ist wiederum ein SET vom Photokatalysator zum Amino-Metallkomplex, der letztlich einen Ni III -Komplex erzeugt, der durch reduktive Eliminierung 104 liefert (Schema 26 b). [92] Protonengekoppelter Elektronentransfer (PCET) ermçglicht die Aktivierung von N-H-Bindungen. Neben Anilinderivaten werden auch 3-Aminopyridin und Sulfonamide umgesetzt.…”

Section: C-n-bindungsbildungunclassified

Photokatalyse mit sichtbarem Licht: Welche Bedeutung hat sie für die organische Synthese?

et al. 2018

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Die Photokatalyse mit sichtbarem Licht hat sich im letzten Jahrzehnt zu einer breit angewandten Methode in der organischen Synthese entwickelt. Für viele wichtige Reaktionen, wie Kreuzkupplungen, α‐Amino‐Funktionalisierungen, Cycloadditionen, ATRA‐Reaktionen oder Fluorierungen, wurden photokatalytische Varianten berichtet. Um Chemiker bei der Auswahl photokatalytischer Methoden für ihre Synthesen zu unterstützen, vergleichen wir in diesem Aufsatz klassische und photokatalytische Verfahren für ausgewählte Reaktionsklassen und zeigen deren Vorteile und Grenzen auf. In vielen Fällen verlaufen die photokatalytischen Reaktionen unter milderen Reaktionsbedingungen, typischerweise bei Raumtemperatur, und stöchiometrische Reagenzien werden durch einfache Oxidanzien oder Reduktionsmittel wie Luft, Sauerstoff oder Amine ersetzt. Beeinflusst die Photokatalyse mit sichtbarem Licht die organische Synthese? Die Aussicht, Elektronen zu Substraten und Zwischenprodukten hin‐ und herzuschieben oder Energie selektiv durch einen sichtbares Licht absorbierenden Photokatalysatoren zu übertragen, verspricht die aktuellen Verfahren in der Radikalchemie zu verbessern und neue Wege durch den Zugang zu reaktiven, bisher unbekannten Spezies zu erschließen, insbesondere durch das Zusammenspiel von Photokatalyse mit der Organo‐ oder Metallkatalyse.

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Kinetics of Dialkylaminium Cation Radical Reactions: Radical Clocks, Solvent Effects, Acidity Constants, and Rate Constants for Reactions with Hydrogen Atom Donors

Cited by 84 publications

References 8 publications

Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines

Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines

The Cleavage of a CC Bond in Cyclobutylanilines by Visible‐Light Photoredox Catalysis: Development of a [4+2] Annulation Method

Photokatalyse mit sichtbarem Licht: Welche Bedeutung hat sie für die organische Synthese?

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