.beta.-Scission of 8-hydrindanoxyl and related free radicals

O'Dell, Dale E.; Loper, John T.; Macdonald, Timothy L.

doi:10.1021/jo00257a006

Cited by 29 publications

(5 citation statements)

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“…Subsequent endo cyclization back onto the oxygen atom of the newly generated carbonyl group yielded unsaturated lactone 81 by an F 4 C 5n sequence the overall effect of which was ring expansion. A similar sequence was also reported by O'Dell et al for a reaction in which an alkoxyl radical was generated using mercuric oxide/iodine 116…”

Section: Two‐stage Unimolecular Free‐radical Cascadesmentioning

confidence: 99%

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

McCarroll

Walton

2001

Angew. Chem. Int. Ed.

236

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Cascade, domino, or tandem processes, that link together two or more transformations in one pot, are increasing in popularity because they lead to improvements in synthetic efficiency and decreases in environmental impact. Not only do these cascades contain choice mechanistic gems but they also deliver compact and elegant syntheses of complex natural products. Longer cascades require more functional groups precisely configured within carefully designed initial molecular architectures. Such “purposeful” molecules can be thought of as chemical algorithms.This article surveys the phenomenal range of unimolecular free‐radical cascades. A convenient system for classifying free‐radical cascades is described that is useful for evaluating and comparing cascades and aids the design of synthetic routes to polycyclic structures.Double cyclization cascades lead to cyclopentylcyclopentane or bicyclo[3.3.0]octane derivatives. Precursors that contain a ring as a template have been used to control stereochemistry in syntheses of triquinanes and many related compounds. Of the cascades containing ring‐cleavage steps, the most useful are the ring expansions which have opened up new synthetic routes to medium ring polycycles.The key design features of three‐stage unimolecular free‐radical cascades that yielded steroid structures, are linear arrays of radical acceptor units associated with methyl groups distributed every fifth C‐atom in the precursor polyenes. Ring cleavage is the reverse of cyclization. In special, symmetrical structures, therefore, this led to sequences that were reversible, thus launching endlessly repeating cascades supported by delightfully fluxional structures. The science of “programming” organic molecules to achieve particular target structures is maturing rapidly. Coordination and classification of the welter of information in this area is intended to facilitate design and hence to extend the range and complexity of attainable structures.

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Section: Two‐stage Unimolecular Free‐radical Cascadesmentioning

confidence: 99%

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

McCarroll

Walton

2001

Angew. Chem. Int. Ed.

236

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“…Model studies were conducted with alkynylcyclopentanone 18a , which was prepared in 47% yield by Eschenmoser fragmentation of epoxy ketone 17 with TsNHNH 2 and HOAc in CH 2 Cl 2 . Silylation of the terminal alkyne by treatment of 18a with 2.3 equiv of LDA and 2.5 equiv of TMSCl and hydrolysis of the silyl enol ether gives 18b in 95% yield.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of (±)-Gymnomitrol. Mn(OAc)₃-Initiated Free-Radical Cyclization of Alkynyl Ketones

1997

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Mn(OAc)(3)-initiated cyclization of alkynyl ketones in 9-19:1 EtOH/HOAc at 90 degrees C is a useful cyclization procedure in favorable cases. Cyclization of (trimethylsilyl)alkynyl ketone 4e provides 62% of silylalkenes 26 and 27 in the key reaction of a seven-step (16% overall yield) synthesis of gymnomitrol (1) from readily available ketone 23. 9alpha-Hydroxygymnomitryl acetate (2) and 9-oxogymnomitryl acetate (3) have been prepared from gymnomitrol. Cyclization of propargyl cyclohexanones 39a-c provides bicyclic compounds 40-42 in 40-60% yield.

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“…Later, Macdonald and co-workers concluded that a similar interplay of kinetic and thermodynamic factors also determines the alkoxy radical β-scission of several structurally related hydrindan-8-ol (977a,b and 981) and hydrinden-8ol systems (983, 986; Scheme 256). 382 However, a priori considerations concerning the mode of β-scission in these cyclic systems remained tenuous.…”

Section: Ring-openingmentioning

confidence: 99%

Synthesis of β-, γ-, δ-, ..., ω-Halogenated Ketones and Aldehydes

2010

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.beta.-Scission of 8-hydrindanoxyl and related free radicals

Cited by 29 publications

References 1 publication

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Synthesis of (±)-Gymnomitrol. Mn(OAc)₃-Initiated Free-Radical Cyclization of Alkynyl Ketones

Synthesis of β-, γ-, δ-, ..., ω-Halogenated Ketones and Aldehydes

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.beta.-Scission of 8-hydrindanoxyl and related free radicals

Cited by 29 publications

References 1 publication

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Synthesis of (±)-Gymnomitrol. Mn(OAc)3-Initiated Free-Radical Cyclization of Alkynyl Ketones

Synthesis of β-, γ-, δ-, ..., ω-Halogenated Ketones and Aldehydes

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Synthesis of (±)-Gymnomitrol. Mn(OAc)₃-Initiated Free-Radical Cyclization of Alkynyl Ketones