Photoinduced molecular transformations. Part 138. A new route to dibenzo[a,d]cycloalkanes and their naphtho analogues via the ring expansion of benzocyclobutenols involving a selective β-scission of cyclobutenoxyl radicals generated by photolysis of their hypoiodites

Kobayashi, Kazuhiro; Konishi, Atsushi; Itoh, Mitsuomi; Suginome, Hiroshi

doi:10.1039/p19930000825

Cited by 10 publications

(3 citation statements)

References 35 publications

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“…Suginome et al have observed fragmentation in tetracyclic alcohol 517 upon irradiation in the presence of I 2 O−I 2 to give two carbon ring expanded dibenzocyclooctanes 518 and 519 in preparatively useful yields, Scheme 106 …”

Section: B Radical-mediated Ring Expansionsmentioning

confidence: 99%

“…[217][218][219][220][221] These ring expansions An elegant radical-induced fragmentation cyclization sequence in 508 to deliver an annulated eightmembered ring through the intermediacy of an oxycyclopropyl radical 509, ring expansion to 510, and interception of this radical by pendant alkynyl chain to give the annulated cyclooctanone 511 has been reported by Boger and Mathvink, Scheme 104. 222 One carbon expansion route to annulated cyclooctanoids via cyclopropyl systems has also been explored by Iwasawa et al 224 Galatsis et al have observed 225 a two carbon ring expansion in epoxy iodide 520 to furnish cyclooctanone 521, Scheme 107. 225 Several related examples involving the epoxy decalins 522 and 523 and leading to fused 524, 525 and bridged cyclooctanes 526 have been reported, Scheme 107.…”

Section: B Radical-mediated Ring Expansionsmentioning

confidence: 99%

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Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

1999

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Section: B Radical-mediated Ring Expansionsmentioning

confidence: 99%

Section: B Radical-mediated Ring Expansionsmentioning

confidence: 99%

Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

1999

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“…In general, two-carbon ring expansion reactions are observed as indicated (Eq. 2) [30]. One-carbon ring-expanded unsaturated ketones can be obtained by treatment of 1-[(trimethylsilyl)oxy] bicyclo[n.l.0]alkanes, where n can take values 1, 2, 3 or 8 with iron trichloride.…”

Section: Fragmentation Of Alcoholsmentioning

confidence: 99%

β‐Fragmentation of Alkoxyl Radicals: Synthetic Applications

Suárez¹,

Rodríguez²

2001

Radicals in Organic Synthesis

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The /?-fragmentation reaction is the reversible homolytic cleavage of a C-C bond a,P to an alkoxyl radical (I) which gives rise to a carbon radical and a C-0 double bond (11) (Scheme 1) [ 11. The equilibrium is strongly displaced to the fragmented Cradical (11). This is especially more pronounced in cyclopentane or smaller ring systems, or in a-substituted systems (R = alkyl, allyl, aryl) where the radical could be stabilized. For the cyclopentyloxyl radical, the equilibrium constant k,-/k, is approximately 2000, while it is only 10 for the cyclohexanyloxyl radical [2]. The formation of the final products 111 and IV is strongly influenced not only by the equilibrium constant but also by kl and k2, and the reaction can be best interpreted by using the Curtin-Hammett kinetic principle (31. In some cases when the reagent used reacts much faster with alkoxyl radicals than with carbon radicals (kl >> kz), the reverse cyclization reaction is possible and alkyl radicals can add intramolecularly to aldehydes or ketones generating alkoxyl radicals despite the unfavorable equilibrium [4].The regioselectivity of the fragmentation is not always apparent. In most cases the more stable radical is formed, but the different constants of equilibrium must be taken into account. A study of the fragmentation of 9-decalinoxyl radicals realized by Beckwith et al. is a good example of this [5]. Rearrangement at 0°C of 9-decalinyl hypobromite gives 6-bromocyclodecanone, whereas 2-(4-bromobutyl)-cyclohexanone is obtained at 8 1 "C. The increase in temperature displaces the equilibrium to the formation of an a priori less stable primary radical. The effect of alkyl substituents and ring size on the regioselectivity of the alkoxyl radical fragmentation has recently been evaluated by computational methods [6]. The importance of the activation energy and the energy of the reaction has been examined for a variety of cyclic and acyclic alkoxyl radicals. Radicals in Organic Synthesis Edited

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The Application of Cyclobutane Derivatives in Organic Synthesis

Chan

2009

Patai's Chemistry of Functional Groups

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Photoinduced molecular transformations. Part 138. A new route to dibenzo[a,d]cycloalkanes and their naphtho analogues via the ring expansion of benzocyclobutenols involving a selective β-scission of cyclobutenoxyl radicals generated by photolysis of their hypoiodites

Cited by 10 publications

References 35 publications

Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

β‐Fragmentation of Alkoxyl Radicals: Synthetic Applications

The Application of Cyclobutane Derivatives in Organic Synthesis

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