6.19 Fragmentation Reactions

Hoang, Tung T.; Dudley, Gregory B.; Williams, Lawrence J.

doi:10.1016/b978-0-08-097742-3.00630-3

Cited by 10 publications

(8 citation statements)

References 87 publications

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“…This is the shortest and highest yielding synthesis of any illudalane sesquiterpene of which we are aware, which illustrates the utility of neopentyl-tethered 1,6-enynes as building blocks for synthesis of important goal structures that contain the gemdimethyl-cyclopentane structural motif. This relatively concise and efficient synthesis more broadly highlights the strategic pairing 23 of fragmentation 24 and cycloisomerization 7 processes for preparing challenging ring systems.…”

mentioning

confidence: 99%

Six-Step Synthesis of Alcyopterosin A, a Bioactive Illudalane Sesquiterpene with a gem-Dimethylcyclopentane Ring

et al. 2016

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Strategic pairing of ring openings and cycloisomerization provides rapid and efficient "open and shut" entry into sparsely functionalized illudalanes, as exemplified here in the context of a six-step synthesis of alcyopterosin A. Key steps include a tandem ring-opening fragmentation/olefination process for preparing a neopentyl-tethered 1,6-enyne, ring-opening olefination telescoped with alkyne homologation, and Rh-catalyzed oxidative cycloisomerization.

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confidence: 99%

Six-Step Synthesis of Alcyopterosin A, a Bioactive Illudalane Sesquiterpene with a gem-Dimethylcyclopentane Ring

et al. 2016

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“…Remarkably, despite the intriguing and appealing structural and potential reactivity features of 3-alkoxy-1-N-toluenesulfonyl azopropenes [3][4][5] and related species, almost nothing has been reported in the literature aside from the fragmentation reaction mentioned above. 6,7 A notable exception to this was a study reported by Fuchs in 1976, 8 in which he recognized a deeper synthetic potential for this intermediate. In that instance, Fuchs was able to trap the 3-alkoxy-1-N-toluenesulfonyl azopropene moiety with phenyl copper, which prevented fragmentation and led to a fundamentally new approach to the synthesis of b-hydroxy ketones ( Figure 1B).…”

Section: Introductionmentioning

confidence: 99%

Stereodivergent Synthesis of β,γ-Fused Bicyclic γ-Lactones via a Multicomponent Ring-Expansion Cascade

Rastelli

Bolinger

Coltart

2018

Chem

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The 3-alkoxy-1-N-toluenesulfonyl azopropene structural motif has been known in the context of the Eschenmoser-Tanabe fragmentation for over 50 years. It is derived from a-epoxy N-toluenesulfonyl hydrazones by deprotonation and epoxide ring opening. A very interesting yet unreported feature of these intermediates is their putative 1,3-dipolar nature and the potential to use them in reactions with complimentary dipoles to enable novel ring-expansion methods for the synthesis of saturated and partially saturated oxygen heterocycles. Herein, we describe such a transformation that requires the simple combination of an ester or acyl pyrrole, an a-epoxy 2-nitrophenyl hydrazone, and a commercially available base (KHMDS or LiHMDS) and leads to the highly (up to >25:1) diastereoselective synthesis of b,g-fused bicyclic g-lactones (an important class of chiral oxygen heterocycles), including those with quaternary centers. Conveniently, both synand anti-fused bicyclic systems can be generated stereoselectively through a simple modification of the reaction conditions.

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“…33,34 Heterolytic fragmentation reactions (e.g., 2 → 3) can be useful strategic tools in organic synthesis. [35][36][37][38][39][40][41] When applied successfully, fragmentation reactions can effect ringexpansion 42,43 -see, for example, the total synthesis of vinigrol. 44 Examples in which fragmentation reactions have been useful continue to emerge in the literature (e.g., in bioorthogonal self-immolative linkers) 45 and we suspect their utility will only continue to expand.…”

Section: Introductionmentioning

confidence: 99%

The Role of Through-Bond Stereoelectronic Effects in the Reactivity of 3-Azabicyclo[3.3.1]nonanes

Laconsay

Rho

Tantillo

2021

Preprint

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Hyperconjugation/conjugation through-bond stereoelectronic effects were studied with density functional theory (DFT) in the context of 3-azabicyclo[3.3.1]nonanes to unravel puzzling differences in reactivity between a vinylogous chloride (4) and a vinylogous ester (5). These compounds—whose structures differ only by one substituent—were found to display strikingly different reactivities in hydrochloric acid by Risch and co-workers (J. Am. Chem. Soc. 1991, 113, 9411–9412). Computational analyses of substituent effects, noncovalent interactions, natural bond orbitals, isodesmic reactions, and hydration propensities lead to a model for which the role of remote, through-bond stereoelectronic effects is key to explaining 4 and 5’s diverging reactivity.

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6.19 Fragmentation Reactions

Cited by 10 publications

References 87 publications

Six-Step Synthesis of Alcyopterosin A, a Bioactive Illudalane Sesquiterpene with a gem-Dimethylcyclopentane Ring

Six-Step Synthesis of Alcyopterosin A, a Bioactive Illudalane Sesquiterpene with a gem-Dimethylcyclopentane Ring

Stereodivergent Synthesis of β,γ-Fused Bicyclic γ-Lactones via a Multicomponent Ring-Expansion Cascade

The Role of Through-Bond Stereoelectronic Effects in the Reactivity of 3-Azabicyclo[3.3.1]nonanes

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