Cycloaddition Reactions

Szpilman, Alex M.; Carreira, Erick M.

doi:10.1002/9780470597521.ch2

Cited by 11 publications

(2 citation statements)

References 95 publications

(62 reference statements)

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“…The observed stereoselectivity from the opening of the prochiral oxetane was attributed to the preference for at ransition structure involving bidentate chelation between the central ring oxygen and that of the oxetane to the Ag I center.N otably,b identate chelation of Ag I salts has previously been exploitedi na ldol reactions [24] and [3+ +2] cycloadditions. [25] The pro-S transition structure 49 does not simultaneously allow for ab identate chelation with Ag I and required orbital alignment. The formation of the tricyclic spiroacetals 46 and 47 as a3:2 diastereomeric mixture is consistent with previouss yntheses of 5,5-spiroacetals as anomeric mixtures.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis and Configurational Assignment of Ascospiroketal A

Chang

Hur

Britton

2015

Chemistry A European J

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The total synthesis of the marine fungus-derived natural product ascospiroketal is described. This concise synthesis relies on a unique Ag(I) -promoted tandem cascade cyclization that provides direct access to the correctly configured tricyclic core of the natural product from a linear precursor. The synthesis of candidate stereostructures of ascospiroketal A allowed for the confident assignment of both the relative and absolute stereochemistry of this unusual octaketide.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis and Configurational Assignment of Ascospiroketal A

Chang

Hur

Britton

2015

Chemistry A European J

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“…4) 44 . The entire scaffold was assembled in a single synthetic step through the [3 þ 2] cycloaddition of commercially available naphthoquinone 18 with imines 19 (R ¼ mesityl (mes) or naphthyl (naph)) 45,46 . It was found that the initial bisnaphthol product 21a,b is rapidly oxidized to the quinone 22a,b when exposed to air during workup.…”

Section: Resultsmentioning

confidence: 99%

Design concept for α-hydrogen-substituted nitroxides

et al. 2015

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Stable nitroxides (nitroxyl radicals) have many essential and unique applications in chemistry, biology and medicine. However, the factors influencing their stability are still under investigation, and this hinders the design and development of new nitroxides. Nitroxides with tertiary alkyl groups are generally stable but obviously highly encumbered. In contrast, a-hydrogen-substituted nitroxides are generally inherently unstable and rapidly decompose. Herein, a novel, concept for the design of stable cyclic a-hydrogen nitroxides is described, and a proof-of-concept in the form of the facile synthesis and characterization of two diverse series of stable a-hydrogen nitroxides is presented. The stability of these unique a-hydrogen nitroxides is attributed to a combination of steric and stereoelectronic effects by which disproportionation is kinetically precluded. These stabilizing effects are achieved by the use of a nitroxide co-planar substituent in the g-position of the backbone of the nitroxide. This premise is supported by a computational study, which provides insight into the disproportionation pathways of a-hydrogen nitroxides.

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Silver‐Promoted [3+1+1] Annulation of Isocyanoacetates with Nitrosoarenes

et al. 2018

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3+ +1+ +1] annulation of isocyanoacetates with nitrosoarenes for the preparation of 1,4,5-trisubstituted imidazoles or 4,5-dihydro-1H-imidazoles has been disclosed. Isocyanoacetates serve as both at hree-atom component and ao ne-carbonu nit in the reaction. Specially, with catalytic amounts of Ag 2 CO 3 and ar educed temperature this [3+ +1+ +1] annulation of isocyanoacetates enablest he formation of trans-imidazolines in good yield and with high diastereoselectivity.S ilver plays ac ritical dual role:i )ast he catalyst for the efficiency to activate the isocyanides and ii)the oxidantina romatization process.

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Cycloaddition Reactions

Cited by 11 publications

References 95 publications

Total Synthesis and Configurational Assignment of Ascospiroketal A

Total Synthesis and Configurational Assignment of Ascospiroketal A

Design concept for α-hydrogen-substituted nitroxides

Silver‐Promoted [3+1+1] Annulation of Isocyanoacetates with Nitrosoarenes

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