Sequential radical cyclization, alkoxy-radical fragmentation, and recyclization processes: a novel method for the synthesis of fused cycloheptanones and cyclooctenones from cyclohexanones

Nishida, Atsushi; Takahashi, Hirobumi; Takeda, Hiroko; Takada, Noriko; Yonemitsu, Osamu

doi:10.1021/ja00158a079

Cited by 76 publications

(18 citation statements)

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“…In the ' ' C spectrum the carbonyl carbon signal is hardly noticed due to rapid keto enol (Table 1 and Table 2). 2~2-3romo-l-cycloheptenylmethyl~cyclohexane-l,3-dione ( 2 ) . IR (KBr) cm-' : 3 1 0 0 , 2 9 0 0 , 1 5 9 0 , 1 4 7 0 , 1 3 0 0 , 1 2 6 5 , 1 2 0~, 1 0 0 …”

Section: Methodsmentioning

confidence: 99%

Alkylation of Cyclic 1,3-Diketones

Rajamannar

Palani

Balasubramanian

1993

Synthetic Communications

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Section: Methodsmentioning

confidence: 99%

Alkylation of Cyclic 1,3-Diketones

Rajamannar

Palani

Balasubramanian

1993

Synthetic Communications

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“…A remarkably intricate C 6x F 4i C 5x C 3x F 3i sequence, that contained two separate ring expansions, ended in the formation of bicyclic oxime ether 107 (Scheme ) 142. Other syntheses involving CF sequences have been reported 143, 144…”

Section: Three‐stage and Longer Unimolecular Cascadesmentioning

confidence: 99%

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

McCarroll

Walton

2001

Angew. Chem. Int. Ed.

233

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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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“…54 The vinyl radical 126 formed after radical addition to the terminal end of the alkyne bond in 124 cyclizes to the carbonyl group in a 6-exo fashion. The resulting alkoxyl radical 127 undergoes acleavage to produce the tertiary radical 128, which is donor stabilized by the aheteroatom (it should be noted that capto-stabilizing groups in a-position lead to significant reduction in the overall reaction rate).…”

Section: Scheme 222mentioning

confidence: 99%

Intermolecular Radical Additions to Alkynes: Cascade‐Type Radical Cyclizations

Wille

2009

Carbon‐Centered Free Radicals and Radical Cations

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Sequential radical cyclization, alkoxy-radical fragmentation, and recyclization processes: a novel method for the synthesis of fused cycloheptanones and cyclooctenones from cyclohexanones

Cited by 76 publications

References 0 publications

Alkylation of Cyclic 1,3-Diketones

Alkylation of Cyclic 1,3-Diketones

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

Intermolecular Radical Additions to Alkynes: Cascade‐Type Radical Cyclizations

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