From 5-Hydroxynicotinic Acid to Nitrogenous (4+3)-Cycloadducts

Harmata, Alexander S.

doi:10.15227/orgsyn.097.0139

Cited by 4 publications

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“…In summary, we report that the intramolecular [2+2] photocycloadditions of 7-azabicyclo[4.3.1]deca-3,8-dien-10-ones, readily available products of the (4+3) cycloaddition of oxidopyridinium ions and dienes, , afford complex polycyclic structures containing the tropane ring system. The process promises to be applicable to many, but not all, such (4+3) cycloadducts, providing rapid access to rigid molecular scaffolds that could be of use in, inter alia, drug development.…”

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“…We have been investigating the intermolecular (4+3) cycloaddition reaction of selected oxidopyridinium ions with dienes and have reported that the process is generally quite effective in terms of yield . Complete control of regioselectivity and endo / exo selectivity remain to be fully optimized, though progress has been made on both fronts. , An example is shown in Scheme . As part of that program, the chemistry of the cycloadducts has become of interest.…”

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“…The precursors used in this study are the (4+3) cycloadducts resulting from the reaction of dienes with the oxidopyridinium ion obtained from 1 upon treatment with base. Their syntheses have been reported elsewhere. , …”

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Tropane Skeleta from the Intramolecular Photocycloaddition of (4+3) Cycloadducts of Oxidopyridinium Ions and Dienes

Sungnoi

et al. 2022

Org. Lett.

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Tropane Skeleta from the Intramolecular Photocycloaddition of (4+3) Cycloadducts of Oxidopyridinium Ions and Dienes

Sungnoi

et al. 2022

Org. Lett.

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(4+3) Cycloadditions of Allylic and Related Cations

Harmata,

Tu,

Clark

2024

Organic Reactions

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The reaction of allylic cations with 1,3‐dienes is formally equivalent to the Diels–Alder reaction but leads to seven‐membered rings. An allylic cation contains 2 pi electrons, and is thus precisely analogous to an alkene and, like the latter, can function as a dienophile. The substituent at the central carbon of the allylic cation serves to terminate the reaction. Most often, this substituent is an oxyanion or a silyl ether, but other groups have been used. These (4+3) cycloadditions can proceed via mechanisms that range from stepwise to concerted. Diastereoselectivity, regioselectivity, and enantioselectivity have all been achieved, though there are still opportunities for the development of new reactions in this area. Asymmetric catalysis and enzymatic catalysis of such reactions is in its infancy. More recent advances center on cations that are related to benzylic cations but involve electron rich heterocycles such as furans, indoles, thiophenes and related structures. This chapter covers advances in (4+3) cycloadditions of allylic and related cations from 1997 to 2017, with supplemental references added to bring the work up to date through 2023. It illustrates both the growth in technical progress and theoretical understanding of this reaction during that time.

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Intramolecular (4+3) Cycloadditions of Oxidopyridinium Ions: Towards Daphnicyclidin A

Ripa

Kelley

et al. 2022

Chemistry A European J

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N-alkylation of 5-hydroxynicotinic acid esters with electrophiles containing diene functionality produces salts that undergo intramolecular (4 + 3) cycloaddition reactions upon heating in the presence of base. Initial studies used a three-carbon tether to join the pyridinium ion and diene, revealing some aspects of the inherent selectivity of the reaction with such substrates. Much more challenging was the synthesis of related species possessing only a two-carbon tether. Nevertheless, the cycloaddition of such compounds was successful, leading directly to the ABC ring system of the alkaloid daphnicyclidin A.

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From 5-Hydroxynicotinic Acid to Nitrogenous (4+3)-Cycloadducts

Cited by 4 publications

References 0 publications

Tropane Skeleta from the Intramolecular Photocycloaddition of (4+3) Cycloadducts of Oxidopyridinium Ions and Dienes

Tropane Skeleta from the Intramolecular Photocycloaddition of (4+3) Cycloadducts of Oxidopyridinium Ions and Dienes

(4+3) Cycloadditions of Allylic and Related Cations

Intramolecular (4+3) Cycloadditions of Oxidopyridinium Ions: Towards Daphnicyclidin A

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