A New Sequential Intramolecular Cyclization Based on the Boekelheide Rearrangement

Massaro, Assunta; Mordini, Alessandro; Mingardi, Anna; Klein, Jens; Andreotti, Daniele

doi:10.1002/ejoc.201000936

Cited by 14 publications

(5 citation statements)

References 30 publications

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“…Acylation of heterocyclic N -oxides, namely, the Boekelheide rearrangement (see section ), is usually employed for functionalization of the carbon side chain. Silylation of pyridine N -oxide derivatives 57 proved useful in the intramolecular trapping of the pycolylic cation A (Scheme ) . For this purpose di- tert -butylsilyl bis(trifluoromethanesulfonate) was used.…”

Section: [1x]-rearrangements (X = 3 5 7) Of N-oxyenaminesmentioning

confidence: 99%

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Rearrangement of N-Oxyenamines and Related Reactions

2014

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Section: [1x]-rearrangements (X = 3 5 7) Of N-oxyenaminesmentioning

confidence: 99%

“…Silylation of pyridine N-oxide derivatives 57 proved useful in the intramolecular trapping of the pycolylic cation A (Scheme 19). 45 For this purpose di-tert-butylsilyl bis(trifluoromethanesulfonate) was used. Microwave irradiation raises the yields by 13−26%, compared to those achieved at room temperature.…”

Section: X-migrationsmentioning

confidence: 99%

Rearrangement of N-Oxyenamines and Related Reactions

2014

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“…Treatment of pyrimidine N -oxide PO13 with acetic anhydride at 90 °C furnished the expected pyrimidine derivative PM61 in 69% yield [32] showing that this transformation involves an internal redox reaction. However, the mechanism of this rearrangement is still under discussion [56–57] and side-products such as PM62 having a 4-ethyl group (3% yield) and other compounds evidence the participation of radicals [30]. After the efficient conversion of pyrimidine N -oxide PO14 into pyrimidine PM63 no products of this type were isolated.…”

Section: Reviewmentioning

confidence: 99%

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

Lechel

Kumar

Bera

et al. 2019

Beilstein J. Org. Chem.

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The LANCA three-component reaction of lithiated alkoxyallenes LA, nitriles N and carboxylic acids CA leads to β-ketoenamides KE in good to excellent yields. The scope of this reaction is very broad and almost all types of nitriles and carboxylic acids have successfully been used. The alkoxy group introduced via the allene component is also variable and hence the subsequent transformation of this substituent into a hydroxy group can be performed under different conditions. Enantiopure nitriles or carboxylic acids can also be employed leading to chiral KE with high enantiopurity and dinitriles or dicarboxylic acids also lead to the expected bis-β-ketoenamides. β-Ketoenamides incorporate a unique combination of functional groups and hence a manifold of subsequent reactions to highly substituted heterocyclic compounds is possible. An intramolecular aldol-type condensation reaction efficiently furnishes pyridin-4-ols PY that can be further modified by palladium-catalyzed reactions, e.g., to specifically substituted furopyridine derivatives. Condensations of β-ketoenamides with ammonium salts or with hydroxylamine hydrochloride afford pyrimidines PM or pyrimidine N-oxides PO with a highly flexible substitution pattern in good yields. The functional groups of these heterocycles also allow a variety of subsequent reactions to various pyrimidine derivatives. On the other hand, acid-labile alkoxy substituents such as a 2-(trimethylsilyl)ethoxy group are required for the conversion of β-ketoenamides into 5-acetyl-substituted oxazoles OX, again compounds with high potential for subsequent functional group transformations. For acid labile β-ketoenamides bearing bulky substituents the acid treatment leads to acylamido-substituted 1,2-diketones DK that could be converted into quinoxalines QU. All classes of heterocycles accessed through the key β-ketoenamides show a unique substitution pattern – not easily accomplishable by alternative methods – and therefore many subsequent reactions are possible.

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“…Compound 13 was obtained as yellow oil (21 mg, 14%) after purification by column chromatography on silica using ethyl acetate as the eluent. Spectroscopic data matched with those reported in the literature …”

Section: Experimental Sectionmentioning

confidence: 99%

“…Spectroscopic data matched with those reported in the literature. 21 1 H NMR (500 MHz, CDCl 3 , ppm): δ 8.49 (d, J = 4.6 Hz, 1H), 7.58 (td, J = 7.6, 1.5 Hz, 1H), 7.15 (d, J = 7.9 Hz, 1H), 7.10 (dd, J = 6.9, 5.3 Hz, 1H), 3.67 (t, J = 6.4 Hz, 2H), 2.83 (t, J = 7.6 Hz, 2H), 1.83 (p, J = 7.6 Hz, 2H), 1.60−1.67 (m, 2H).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Total Synthesis of Phenanthroquinolizidine Alkaloids Using a Building Block Strategy

Cheon

2019

J. Org. Chem.

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A concise and general strategy for the total synthesis of the phenanthroquinolizidine alkaloids has been developed. An iterative Suzuki−Miyaura coupling reaction between the requisite aryl boronic acid, 2-bromo-4,5dimethoxyphenyl N-methyliminodiacetate (MIDA) boronate derived from boronic acid, and a suitable bromopyridine substrate bearing a homopropargyl alcohol at the 2-position generated the desired ortho-aza-terphenyl compounds. Hydrogenation of the triple bond followed by treatment with methanesulfonyl chloride afforded their corresponding tetrahydroquinolizinium ion intermediates, which were subsequently reacted with NaBH 4 to provide the desired hexahydroquinolizine products. A final oxidative electrocyclization reaction gave the target phenanthroquinolizidine natural products. This synthetic approach only requires the use of three chromatographic separations throughout the entire synthesis.

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A New Sequential Intramolecular Cyclization Based on the Boekelheide Rearrangement

Abstract: Pyrrolidines and piperidines were synthesized from (aminoalkyl)pyridine N-oxides with a general and quite efficient method developed by using di-tert-butylsilyl bis(trifluoromethanesulfonate) as a new promoter for a Boekelheide-type

Cited by 14 publications

References 30 publications

Rearrangement of N-Oxyenamines and Related Reactions

Rearrangement of N-Oxyenamines and Related Reactions

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

Total Synthesis of Phenanthroquinolizidine Alkaloids Using a Building Block Strategy

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