Complex examples of the Dowd–Beckwith rearrangement: a free radical route to 2-oxabicyclo 〚3.3.0〛octan-3,6-diones

Hart, David J.; Havas, F.

doi:10.1016/s1387-1609(01)01274-9

Cited by 4 publications

(5 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In 2001, Hart and coworkers discovered a Dowd–Beckwith/allylation sequence to access 2‐oxabicyclo [3.3.0] octan‐3,6‐diones (Scheme 28). [40] The reaction of iodooxabicyclo [3,2,1] octanes with allyltributyltin and AIBN in refluxing benzene led to the formation of allylated fused bicyclic compounds 126 – 128 in moderate to good yields as single diastereomers. The proposed mechanism involves the intramolecular addition of secondary alkyl radical I to the ketone to give the cyclopropyloxy radical II .…”

Section: Promoted By Tributyltin Hydridementioning

confidence: 99%

The Dowd–Beckwith Reaction: History, Strategies, and Synthetic Potential

Singha

Mondal

Midya

et al. 2022

Chemistry A European J

View full text Add to dashboard Cite

Ring-expansion strategies are valuable synthetic tools that take benefit of existing ring structures and evade the unfavorable enthalpic-and entropic effects that arise with end-to-end cyclizations. One potentially important class of such reactions is the Dowd-Beckwith reaction, the ringexpansion of ketones via alkoxy radicals. The exciting advancement in this research area is starting to show its potential, as demonstrated by applying this methodology in strategy-level bond formation to synthesize complex natural products. This Review aims to provide the first comprehensive survey of the development of the Dowd-Beckwith reaction spanning three decades from the initial report to the present day, thus providing the readers with great detail about the contributions of this reaction to organic synthesis. We hope that this review will further disclose the salient features of the Dowd-Beckwith reaction for synthetic applications and encourage the development of new, more advanced applications.

show abstract

Section: Promoted By Tributyltin Hydridementioning

confidence: 99%

The Dowd–Beckwith Reaction: History, Strategies, and Synthetic Potential

Singha

Mondal

Midya

et al. 2022

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…The Dowd–Beckwith rearrangement is a radical-mediated skeletal rearrangement that has found synthetic applications in ketone ring expansions. − Typically, a primary alkyl radical is generated by halogen abstraction with a stannyl radical. This then adds to a carbonyl, forming a cyclopropyloxy radical which subsequently undergoes β-scission to give a more stable radical that is then quenched with tributyltin hydride (Scheme A).…”

mentioning

confidence: 99%

Iron-Catalyzed Photoinduced LMCT: A 1° C–H Abstraction Enables Skeletal Rearrangements and C(sp³)–H Alkylation

2021

View full text Add to dashboard Cite

Herein we disclose an iron-catalyzed method to access skeletal rearrangement reactions akin to the Dowd–Beckwith ring expansion from unactivated C(sp3)–H bonds. Photoinduced ligand-to-metal charge transfer at the iron center generates a chlorine radical, which abstracts electron-rich C(sp3)–H bonds. The resulting unstable alkyl radicals can undergo rearrangement in the presence of suitable functionality. Addition to an electron deficient olefin, recombination with a photoreduced iron complex, and subsequent protodemetalation allow for redox-neutral alkylation of the resulting radical. Simple adjustments to the reaction conditions enable the selective synthesis of the directly alkylated or the rearranged-alkylated products. As a radical clock, these rearrangements also enable the measurement of rate constants of addition into various electron deficient olefins in the Giese reaction.

show abstract

“…Iodide exchange of 1 catalyzed by substrates containing 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) allowed such access. Utilizing the procedure described by Boger, 1a was heated with TEMPO (5 equiv) and n -Bu 3 SnH (3 equiv) in benzene to give 18 and 19 in 21 and 61% yield, respectively . Predominant formation of 19 over 18 is a consequence of the preferential equatorial approach of TEMPO to the resulting secondary radical in a way that relieves 1,3-interaction with the axial hydrogen atom at C-5 .…”

Section: Resultsmentioning

confidence: 99%

Novel Fragmentation Reaction of 2-Alkyl- and 2,4-Dialkyl-3-iodo-1-oxocyclohexan-2,4-carbolactones

et al. 2004

View full text Add to dashboard Cite

2-Alkyl- and 2,4-dialkyl-3-iodo-1-oxocyclohexan-2,4-carbolactones undergo lithium hydroxide- and lithium alkoxide-induced fragmentation reactions to provide butenolides, gamma-hydroxycyclohexenones, and/or gamma-butyrolactones. In general, product distribution is governed by two factors: (1) the nature of nucleophiles and (2) the steric bulkiness of the substituents at C-2 and C-4 of the cyclohexanones. Lithium hydroxide-induced fragmentation provides butenolides and gamma-hydroxycyclohexenones. In contrast, lithium alkoxide-promoted fragmentation results in predominantly 5-substituted gamma-butyrolactones along with a small amount of butenolides in limited cases. Fragmentation products induced by lithium hydroxide are largely influenced by the steric bulkiness of the substituents at C-2 and C-4 of the cyclohexanone ring. The bulky substituents render the exclusive formation of butenolides.

show abstract

Complex examples of the Dowd–Beckwith rearrangement: a free radical route to 2-oxabicyclo 〚3.3.0〛octan-3,6-diones

Cited by 4 publications

References 19 publications

The Dowd–Beckwith Reaction: History, Strategies, and Synthetic Potential

The Dowd–Beckwith Reaction: History, Strategies, and Synthetic Potential

Iron-Catalyzed Photoinduced LMCT: A 1° C–H Abstraction Enables Skeletal Rearrangements and C(sp³)–H Alkylation

Novel Fragmentation Reaction of 2-Alkyl- and 2,4-Dialkyl-3-iodo-1-oxocyclohexan-2,4-carbolactones

Contact Info

Product

Resources

About

Complex examples of the Dowd–Beckwith rearrangement: a free radical route to 2-oxabicyclo 〚3.3.0〛octan-3,6-diones

Cited by 4 publications

References 19 publications

The Dowd–Beckwith Reaction: History, Strategies, and Synthetic Potential

The Dowd–Beckwith Reaction: History, Strategies, and Synthetic Potential

Iron-Catalyzed Photoinduced LMCT: A 1° C–H Abstraction Enables Skeletal Rearrangements and C(sp3)–H Alkylation

Novel Fragmentation Reaction of 2-Alkyl- and 2,4-Dialkyl-3-iodo-1-oxocyclohexan-2,4-carbolactones

Contact Info

Product

Resources

About

Iron-Catalyzed Photoinduced LMCT: A 1° C–H Abstraction Enables Skeletal Rearrangements and C(sp³)–H Alkylation