1,3‐Benzyl Migration in Iminium Ions: Evidence for a Fast Free‐Radical Chain Reaction

Blank, Nancy; Straub, Bernd F.; Opatz, Till

doi:10.1002/ejoc.201101183

Cited by 9 publications

(7 citation statements)

References 42 publications

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“…A related rearrangement has been observed in 1-benzyl-2-methylene-1,2,3,4-tetrahydroisoquinolin-2-ium salts by Blank et al (Scheme 18) [49]. A free radical mechanism was supported by the observation of reaction inhibition by iodine, cuprous chloride or TEMPO and rate acceleration by radical initiators like dibenzoyl peroxide.…”

Section: Addition To Aliphatic Iminium Ionsmentioning

confidence: 62%

Radical Addition to Iminium Ions and Cationic Heterocycles

2014

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Carbon-centered radicals represent highly useful reactive intermediates in organic synthesis. Their nucleophilic character is reflected by fast additions to electron deficient C=X double bonds as present in iminium ions or cationic heterocycles. This review covers diverse reactions of preformed or in situ-generated cationic substrates with various types of C-radicals, including alkyl, alkoxyalkyl, trifluoromethyl, aryl, acyl, carbamoyl, and alkoxycarbonyl species. Despite its high reactivity, the strong interaction of the radical's SOMO with the LUMO of the cation frequently results in a high regioselectivity. Intra-and intermolecular processes such as the Minisci reaction, the Porta reaction, and the Knabe rearrangement will be discussed along with transition metal and photoredox catalysis or electrochemical methods to generate the odd-electron species.

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Section: Addition To Aliphatic Iminium Ionsmentioning

confidence: 62%

Radical Addition to Iminium Ions and Cationic Heterocycles

2014

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“…6 We have found a related 1,3benzyl migration in 1-benzyl-1,2,3,4-tetrahydroisoquinolines (Scheme 1b) and, together with the Straub group, presented evidence for a free radical chain mechanism under kinetic entropy control. 7 Again, a homolytic cleavage of an unstrained C(sp 3 )−C(sp 3 )-σ-bond is involved.…”

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confidence: 99%

Light-Induced Alkylation of (Hetero)aromatic Nitriles in a Transition-Metal-Free C–C-Bond Metathesis

Lipp

Detert

et al. 2017

Org. Lett.

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A light-induced C-C-σ-bond metathesis was achieved through transition-metal-free activation of an unstrained C(sp)-C(sp)-σ-bond in 1-benzyl-1,2,3,4-tetrahydroisoquinolines. A photoredox-mediated single-electron oxidation of these precursor amines yield radical cations which undergo a homolytic cleavage of a C(sp)-C(sp)-σ-bond rather than the well-known α-C-H-scission. The resulting carbon-centered radicals are used in the ipso-substitution of (hetero)aromatic nitriles proceeding through another single-electron transfer-mediated C-C-bond cleavage and formation.

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“…Compound 4 was prepared by C-alkylation of the potassium salt of α-aminonitrile 1 with benzyl bromide 2 utilizing methodology established by our group for the syntheses of various isoquinoline alkaloids [ 5 – 7 ]. Spontaneous dehydrocyanation afforded the 1-benzylated 3,4-dihydroisoquinoline which was subsequently reduced in situ to tetrahydroisoquinoline 3 in a one-pot procedure with sodium borohydride in 63% yield.…”

Section: Resultsmentioning

confidence: 99%

Chromatographically separable rotamers of an unhindered amide

Geffe¹,

Andernach²,

Trapp³

et al. 2014

Beilstein J. Org. Chem.

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SummarySurprisingly stable formamide rotamers were encountered in the tetrahydroisoquinoline and morphinan series of alkaloids. We investigated the hindered rotation around the amide bond by dynamic high-performance liquid chromatography (DHPLC) and kinetic measurements of the interconversion of the rotamers which can readily be separated by HPLC as well as TLC. The experimental results of the different methods were compared to each other as well as to results obtained by DFT calculations.

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1,3‐Benzyl Migration in Iminium Ions: Evidence for a Fast Free‐Radical Chain Reaction

Cited by 9 publications

References 42 publications

Radical Addition to Iminium Ions and Cationic Heterocycles

Radical Addition to Iminium Ions and Cationic Heterocycles

Light-Induced Alkylation of (Hetero)aromatic Nitriles in a Transition-Metal-Free C–C-Bond Metathesis

Chromatographically separable rotamers of an unhindered amide

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