Stereoselectivity in reactions of bicyclo[3.3.0]oct-1-enes

Bourgin, Daniel; Büchel, René; Gerber, P.; Keese, Reinhart

doi:10.1016/s0040-4039(00)76881-x

Cited by 7 publications

(4 citation statements)

References 16 publications

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“…20,30,31 Alkoxy substituted alkenes which do not have an additional a-substituent appear to favor an endoaddition although contradicting data are found in the literature. 29,[31][32][33] Preparatively useful selectivities were reported for the cycloaddition of 2-(trimethylsilyloxy)buta-1,3-diene (12) and related silyl enol ethers to various alkenones (Scheme 6). 34,35 The reaction of compound 12 with cyclopentenone 11 gave the corresponding adduct 13 which was further transformed into a potential pentalenolactone precursor.…”

Section: Methodsmentioning

confidence: 99%

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Bach

1998

Synthesis

300

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Stereoselective intermolecular [2+2]-photocycloaddition reactions of alkenes and Paternò-Büchi reactions are reviewed. For both reactions the regioselectivity and the simple diastereoselectivity which are relevant to the formation of a single product isomer are explained based on representative examples. In the subsequent sections the facial diastereoselectivity induced by the respective reaction partner is treated. Particular emphasis is given on synthetic applications of the cyclobutanes and oxetanes obtained by the photochemical key step. Consecutive reactions are discussed and the potential use of the four-membered ring intermediates is highlighted.

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Section: Methodsmentioning

confidence: 99%

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Bach

1998

Synthesis

300

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“…Such a facial selective addition of alkenes was usually found in the photoreaction with α,β-unsaturated bicyclic enones. Wiesner proposed the pyramidalization of the β-carbon of the excited state by which the initial addition of alkenes was restricted in one side of the cyclic enones 1 ORTEP drawings of (a) homobenzoquinone 1 , substrate; (b) exo - 3e and (c) exo - 3h , the main products of the photoreaction of 1 with 4-methoxystyrene 2e or 3,3-dimethyl-1-butene 2h , respectively.…”

Section: Resultsmentioning

confidence: 99%

Substituent Effects on the Stereochemistry in the [2 + 2] Photocycloaddition Reaction of Homobenzoquinone Derivative with Variously Substituted Alkenes and Alkynes

et al. 2002

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Irradiation of a homobenzoquinone derivative with variously substituted alkenes and alkynes gave the [2 + 2] photocycloadducts, tricyclic diones, almost quantitatively as a mixture of regio- and stereoisomers. The preferred regioisomer for all reactions is attributed to the more stable 1,4-biradical intermediate (major addition mode), and the minor isomer is attributed to the less stable biradical (minor addition mode). A radical trapping experiment using benzeneselenol proved the generation of these two regioisomeric biradicals, reflecting the regioselectivity in selenol-free photoreaction. Both biradicals tended to preferentially yield the endo-isomer for the alkenes with smaller substituents such as ethoxy, cyano, and acetoxy groups, but the exo-isomer for the alkenes with larger substituents such as phenyl, carbazolyl, and tert-butyl groups. The logarithmic exo/endo ratios were well correlated with a combination of Taft's steric factor E(s) and the energy gain (DeltaE') associated with the orbital interactions between the spin centers of 1,4-biradicals. These results were interpreted in terms of Griesbeck's SOC mechanism as well as the possible bond rotation around the armed radical chain. Therefore, it is concluded that a balance of repulsive steric hindrance and the attractive FMO interaction determines the stereochemical course of the [2 + 2] photoaddition of homobenzoquinone derivative with variously substituted alkenes.

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“…5). 61–63 Such molecules require higher temperature (220°C for 40 ) in organic solvent to ensure the desired rearrangement 62,63…”

Section: Claisen Rearrangement Promoted By Hydrophilic Groupsmentioning

confidence: 99%

The Use of Hydrophilic Groups in Aqueous Organic Reactions

Itami

Yoshida

2002

The Chemical Record

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The representative examples of beneficial effects of hydrophilic groups in aqueous organic reactions are described, including the Diels-Alder reactions, hetero Diels-Alder reactions, Claisen rearrangement, radical reactions, and transition metal-catalyzed reactions. Although the low solubility of organic molecules in water has been a bane in aqueous organic reactions, the incorporation of hydrophilic groups into the substrate structure can overcome the solubility problem and at the same time enhance the hydrophobic effect. In some cases, interesting micellar effects are observed because of the amphiphilic natures of such molecules. The emerging concept of "removable hydrophilic group," in which the solubility problems have been alleviated, yet the initial product can still be transformed into a variety of products with the removal of the hydrophilic groups, is also described.

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Stereoselectivity in reactions of bicyclo[3.3.0]oct-1-enes

Cited by 7 publications

References 16 publications

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Substituent Effects on the Stereochemistry in the [2 + 2] Photocycloaddition Reaction of Homobenzoquinone Derivative with Variously Substituted Alkenes and Alkynes

The Use of Hydrophilic Groups in Aqueous Organic Reactions

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