Programmed Polyene Cyclization Enabled by Chromophore Disruption

Solans, Megan; Basistyi, Vitalii S; Law, James A.; Bartfield, Noah M; Frederich, James H.

doi:10.1021/jacs.2c02144

Cited by 11 publications

(6 citation statements)

References 75 publications

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“…We presume that C2À C8 bond during the isomerization (II-A) or after the formation of Z-1 may become highly strained due to the steric interactions between the substituents X and COR, which might facilitate a further photochemical rearrangement. [22] Eventually, IIA can generate the more stable resonance structure II-B to release such strain or it can be directly formed from the intermediary Z-1 under the same reaction conditions. Thus, II-B can undergo 5-exo-trig cyclization with the distal diene unit of the triene system to form further well-stabilized diradical intermediates (III-A/III-B).…”

Section: Chemistry-a European Journalmentioning

confidence: 99%

Integrating Regioselective E→Z Isomerization of Trienones with Cascade Sequences under Photosensitizer‐Free Direct Irradiation at 390 nm

Maity

Ghosh

Das

2023

Chemistry A European J

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The regioselective E!Z isomerization of a target olefin unit embedded in a conjugated polyene is challenging. Examples are limited to retinal and its derivatives only. The problem is further amplified when such an isomerization is integrated into cascade sequences, among which the regioselectivity and subsequent directionality are the major bottlenecks. Indeed, there are no reports till date for such a transformation. Herein, it is reported that such a controlled isomerization and subsequent cyclization cascade can be enabled by photosensitizer-free direct irradiation of linearly conjugated acyclic polyenes in dichloromethane solvent using a 390 nm LED. The directionality results from deconjugation of the extended π-system in the transient Z-isomer due to stabilizing n!π* interactions between 1,4-dicarbonyls (C=O!C=O) or 1,4-carbonyl/-aryl (C=O!aryl) groups. The involvement of such noncovalent interactions has been supported by X-ray crystallography and control experiments. Thus, conjugated trienones can be stereoselectively converted into oxabicyclo[3.2.1]octadienes in an atom-and stepeconomic manner, including the first example by regioselective isomerization of a tetrasubstituted alkene. The reaction conditions are very general (> 46 examples). The reaction can be conducted under open air atmosphere at ambient temperature. Such a cascade cyclization can also be realized in solid state.

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Section: Chemistry-a European Journalmentioning

confidence: 99%

Integrating Regioselective E→Z Isomerization of Trienones with Cascade Sequences under Photosensitizer‐Free Direct Irradiation at 390 nm

Maity

Ghosh

Das

2023

Chemistry A European J

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“…In this regard, it is worthwhile to mention efficient racemic polyene cyclization strategies for the total synthesis of (±)-taxodione [(±)- 1 ] independently developed by Johnson et al (in 1982) and Harring and Livingstone (in 1992) . Recently, Frederich et al (in 2022) developed a programmed polyene cyclization enabled by chromophore disruption for unified total syntheses of abietane diterpenoid, (±)-taxodione [(±)- 1 ] and icetaxane diterpenoid, (±)-salviasperanone . Further, Vanderwal et al (in 20 2 0) reported an elegant cobalt-catalyzed stereocontrolled radical bicyclization approach to oxidized abietane diterpenoids, in particular the total syntheses of (±)-plebedipene B and (+)-2-O-deacetyl plebedipene C (in 2021) .…”

Section: Introductionmentioning

confidence: 99%

Total Synthesis of Diterpenoid Quinone Methide Tumor Inhibitor, (+)-Taxodione

Gavit,

Kundu,

Niyogi

et al. 2024

J. Org. Chem.

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“…To date, a few synthetic approaches have given access to cyclopropanes with contiguous all-carbon quaternary centers via photochemical approaches (Scheme 1C). 58 The Gevorgyan group 59 disclosed that pyridotriazole, a diazo surrogate, could be converted to the corresponding pyridine carbene under UVlight irradiation, and this compound is capable of completing the cyclopropanation reaction. However, only one highly congested cyclopropane bearing contiguous all-carbon quaternary center was afforded.…”

Section: ■ Introductionmentioning

confidence: 99%

Visible-Light-Mediated Energy Transfer Enables Cyclopropanes Bearing Contiguous All-Carbon Quaternary Centers

Xia

Wang

et al. 2023

ACS Catal.

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Cyclopropanes bearing contiguous all-carbon quaternary centers continue to attract attention due to their bioactivities. However, methods to obtain cyclopropanes with contiguous all-carbon quaternary centers remain largely unexplored due to the high steric hindrance of these compounds. Herein, we report a visible-light-mediated energy-transfer (EnT) strategy to realize in situ donor/donor carbenes from readily available N-tosylhydrazones, facilitating the synthesis of highly congested EWG-free cyclopropanes. Through this approach, cyclopropanes are rapidly installed into complex bioactive molecules, fluorescent molecules, and other useful building blocks that are challenging to synthesize. Detailed mechanistic reactions and DFT studies clearly demonstrated the role of the photosensitizer, the formation of donor/donor carbenes, and the necessity of light and a base in the system.

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Programmed Polyene Cyclization Enabled by Chromophore Disruption

Cited by 11 publications

References 75 publications

Integrating Regioselective E→Z Isomerization of Trienones with Cascade Sequences under Photosensitizer‐Free Direct Irradiation at 390 nm

Integrating Regioselective E→Z Isomerization of Trienones with Cascade Sequences under Photosensitizer‐Free Direct Irradiation at 390 nm

Total Synthesis of Diterpenoid Quinone Methide Tumor Inhibitor, (+)-Taxodione

Visible-Light-Mediated Energy Transfer Enables Cyclopropanes Bearing Contiguous All-Carbon Quaternary Centers

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