Asymmetric Photoreactions of Conjugated Enones and Esters

Pete, Jean‐Pierre

doi:10.1002/9780470133521.ch2

Cited by 82 publications

(9 citation statements)

References 308 publications

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“…Indeed, only recently have other natural products but punctaporonin C, that is, taedolidol and 6-epi-taedolidol, been reported, [3b] which incorporate this skeleton. While the cyclobutane ring of oxatetracyclo [6.3.2.0 1,4 .0 5,12 ]tridecane invites a [2 + 2]-photocycloaddition [8,9] it is evident from closer inspection that an intermolecular photocycloaddition, that is, by employing isobutene as a reaction partner, is difficult to achieve at a late stage of the synthesis. A dihydrofuran ring, which would serve as precursor for the central tetrahydrofuran, does not provide an adequate chromophore for irradiation at a reasonable wavelength.…”

Section: Introductionmentioning

confidence: 98%

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Fleck

Bach

2010

Chemistry A European J

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The unique sesquiterpene punctaporonin C was synthesized starting from commercially available 7-tert-butoxynorbornadiene in a linear sequence of 29 steps and with an overall yield of 0.65%. Key step of the synthesis was an intramolecular [2+2]-photocycloaddition, in which the two vinylic double bonds in a 1,3-divinyl-2-cyclopentyl tetronate were differentiated by reaction with the photoexcited tetronate. The reaction gave regio- and diastereoselective access to the tricyclic core skeleton of punctaporonin C in 63% yield. Additional studies related to the tetronate [2+2]-photocycloaddition revealed that even diastereotopic vinylic double bonds in a 1,3-divinyl-2-cyclopentyl tetronate can be differentiated (d.r. up to 78:22). In the further course of the total synthesis the complete tetracyclic oxatetracyclo[6.3.2.0(1, 4).0(5, 12)]tridecane skeleton of punctaporonin C was established by an intramolecular aldol reaction, closing a seven-membered oxepane ring. The nucleophilic methyl ketone employed in this step was generated by Wacker oxidation of the vinylic double bond, which was not involved in the [2+2]-photocycloaddition. Several reactions employed in the synthetic sequence required adaptation to the rigid skeleton of punctaporonin C, for example, the reduction of a mesylate, the alkylation of a cyclobutane carboxylate, or the methyl addition to a prostereogenic carbonyl group.

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Section: Introductionmentioning

confidence: 98%

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Fleck

Bach

2010

Chemistry A European J

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“…It is desirable for a successful intermolecular [2 + 2] photocycloaddition reaction to reach a relatively long-lived excited state, which is available for attack by another olefin. This prerequisite is ideally met by olefinic substrates, the double bond of which is conjugated to a carbonyl group. − Typically, α,β-unsaturated ketones (enones) or α,β-unsaturated carboxylic acid derivatives can be directly excited to the respective S 1 state ( II ) from which intersystem crossing (ISC) (i.e., a spin flip) to the respective triplet state is rapid (Scheme ). Photochemical reactions occur from the lowest-lying triplet state T 1 , which is frequently of ππ* character ( VI )…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

et al. 2016

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The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4, whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.

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“…The GPC result also agrees with this NMR result, and a peak for a polymer of high molecular weight ( M w ) over 10 5 was detected. Nevertheless, there is another possibility that two NBA molecules dimerize with the UV irradiation . However, such dimerized compounds ( M w 256.3) were not detected in the FAB‐MS measurement.…”

Section: Resultsmentioning

confidence: 97%

Initiator‐free photopolymerization of common acrylate monomers with 254 nm light

Furutani

Ide

Kinoshita

et al. 2018

Polymer International

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Using an available light source at a wavelength of 254 nm, common acrylate monomers were polymerized without any photoinitiators, which was confirmed using Fourier transform IR (FTIR) spectroscopy, 1H NMR, gel permeation chromatography and fast atom bombardment mass spectrometric measurements. It was found that phenyl acrylate shows higher conversion than n‐ and t‐butyl acrylates. A trifunctional acrylate was also used for UV curing. The cured films were fabricated successfully on different kinds of substrates by using a batch‐ or conveyor‐type irradiation apparatus. It is indicated from FTIR spectral measurements that ca 40%–50% of acryloyl groups are consumed by the photopolymerization. Oxygen concentration in the sample chamber influences the photopolymerization, indicating that the polymerization proceeds via a radical process. © 2018 Society of Chemical Industry

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Asymmetric Photoreactions of Conjugated Enones and Esters

Cited by 82 publications

References 308 publications

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

Initiator‐free photopolymerization of common acrylate monomers with 254 nm light

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Asymmetric Photoreactions of Conjugated Enones and Esters

Cited by 82 publications

References 308 publications

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Total Synthesis of Punctaporonin C by a Regio‐ and Stereoselective [2+2]‐Photocycloaddition

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

Initiator‐free photopolymerization of common acrylate monomers with 254 nm light

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Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions