Free radical trapping of α-keto radicals derived from α,β-epoxy ketones via photoinduced single electron transfer process

Hasegawa, Eietsu; Ishiyama, Kenyuki; Horaguchi, Takaaki; Shimizu, Takahachi

doi:10.1016/s0040-4039(00)78899-x

Cited by 29 publications

(15 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The initiation step in the absence of AIBN presumably occurs by an electron transfer from allyltributylstannane to these ketones (eq 7). Photoinduced electron transfer reaction from allylstannanes to electron acceptors such as quinones, aromatic ketones, α,β-diketones, and α-epoxy ketones have recently been reported. On the basis of results obtained from studies of the reduction of α-halo ketones and α-(benzoyloxy)acetophenone with tin hydrides, an electron transfer promoted chain mechanism is proposed to account for the formation of addition product, see Scheme .…”

Section: Resultsmentioning

confidence: 99%

On the Mechanism of the Reaction of α-Substituted Ketones with Allyltributylstannane

Chen

Tanner

1996

J. Org. Chem.

View full text Add to dashboard Cite

The mechanisms for the reaction of allyltributylstannane with a number of fragmentation probes, alpha-substituted acetophenones, were studied. All reactions were shown to proceed through free radical chain sequences since they could be initiated by AIBN and inhibited by m-dinitrobenzene (DNB). alpha-Halo- and alpha-(benzoyloxy)acetophenones (I and II, PhCOCR(1)R(2)X; X = F, Cl, Br, OCOPh; R(1), R(2) = H, Me) yielded the allylation products, PhCOCR(1)R(2)CH(2)CH=CH(2)), through a chain sequence involving as the propagation step: an electron transfer from Bu(3)Sn(*) to I and II, fragmentation of the ketyl anion PhCOCR(1)R(2)X(*)(-), and addition of PhCOCR(1)R(2)(*) to allyltributylstannane. The reactions of alpha-(arylsulfonyl)acetophenones (IIIa-c, PhCOCR(1)R(2)Y, Y = SO(2)Tol-p), however, gave a nearly 1:1 mixture of allyl tosyl sulfone and the corresponding ketone, PhCOCHR(1)R(2). The (1)H and (13)C NMR of the reaction mixture between allyltributylstannane and alpha-(p-methylbenzenesulfonyl)isobutyrophenone substantiated the intermediacy of the tin enolate PhC(OSnBu(3))=CMe(2). These results suggested that a radical addition elimination mechanism was involved in the reactions of IIIa-c with allylstannane. The reaction of alpha-phenylthioacetophenone (IV, PhCOCH(2)SPh) gave both the electron transfer and the addition elimination products (PhCOCH(2)CH(2)CH=CH(2), PhCOCH(3)), indicating that both pathways were involved in the formation of the products.

show abstract

Section: Resultsmentioning

confidence: 99%

On the Mechanism of the Reaction of α-Substituted Ketones with Allyltributylstannane

Chen

Tanner

1996

J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…This follows notable earlier reports of α-epoxy-ketone fragmentation upon UV irradiation in the presence of tertiary amine donors. 780 − 782 …”

Section: Reductive Transformations Of Carbonyls Imines and Other X=y Functional Groups Through Photochemical And Electrochemical Pcet Promentioning

confidence: 99%

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

et al. 2021

View full text Add to dashboard Cite

We present here a review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms in which both an electron and a proton are exchanged together, often in a concerted elementary step. As such, MS-PCET can function as a non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from a wide variety of common organic functional groups. We present an introduction to MS-PCET and a practitioner’s guide to reaction design, with an emphasis on the unique energetic and selectivity features that are characteristic of this reaction class. We then present chapters on oxidative N–H, O–H, S–H, and C–H bond homolysis methods, for the generation of the corresponding neutral radical species. Then, chapters for reductive PCET activations involving carbonyl, imine, other X=Y π-systems, and heteroarenes, where neutral ketyl, α-amino, and heteroarene-derived radicals can be generated. Finally, we present chapters on the applications of MS-PCET in asymmetric catalysis and in materials and device applications. Within each chapter, we subdivide by the functional group undergoing homolysis, and thereafter by the type of transformation being promoted. Methods published prior to the end of December 2020 are presented.

show abstract

“…Epoxide 1b has greater quantum yield of the intersystem crossing and a longer triplet lifetime than 1a . In addition to this, the oxidizing ability of the excited 1b should be stronger than that of 1a in light of their reduction potentials . Therefore, the excited triplet state of 1b is expected to oxidize all of the electron donors shown in Chart …”

Section: Resultsmentioning

confidence: 99%

Electron-Transfer Reactions of Aromatic α,β-Epoxy Ketones: Factors That Govern Selective Conversion to β-Diketones and β-Hydroxy Ketones

et al. 1997

Self Cite

View full text Add to dashboard Cite

Photoreaction of trans-1-(4-cyanophenyl)-3-phenyl-2,3-epoxy-1-propanone (trans-4'-cyanochalcone epoxide) with various electron donors was studied. Irradiation of this epoxy ketone with amines produced 1-(4-cyanophenyl)-3-phenyl-1,3-propanedione and 1-(4-cyanophenyl)-3-hydroxy-3-phenyl-1-propanone in various ratios depending on the kinds of amine and solvent used. A reaction mechanism involving an amine cation radical-assisted rearrangement of the epoxy ketone anion radical was proposed to be most consistent with the marked change in the yield of beta-diketone. On the other hand, the timing of proton transfer to the anionic intermediates is considered to be a key factor to yield the beta-hydroxy ketone. Information obtained from the photochemical study was useful to find the reaction conditions for the conversion of several aromatic epoxy ketones to hydroxy ketones by the use of samarium diiodide. Addition of methanol significantly changed the product distribution. Proper choice of water or methanol as a proton source produced hydroxy ketones in moderate to good yields.

show abstract

Free radical trapping of α-keto radicals derived from α,β-epoxy ketones via photoinduced single electron transfer process

Cited by 29 publications

References 10 publications

On the Mechanism of the Reaction of α-Substituted Ketones with Allyltributylstannane

On the Mechanism of the Reaction of α-Substituted Ketones with Allyltributylstannane

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Electron-Transfer Reactions of Aromatic α,β-Epoxy Ketones: Factors That Govern Selective Conversion to β-Diketones and β-Hydroxy Ketones

Contact Info

Product

Resources

About