Heteroatom directed photoarylation. Photochemistry of aryloxyenones

Schultz, Arthur G.; Lucci, Robert D.

doi:10.1021/jo00897a051

Cited by 25 publications

(4 citation statements)

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“…A similar trend is observed with groups in the 8‐position: pyridine 15 (76 % yield), and both electron withdrawing groups (aldehyde 16 , 75 % yield; ester 17 , 95 % yield; nitrile 18 , 86 % yield) and electron donating groups (methoxy 19 , 90 % yield; benzyloxy 20 , 95 % yield; amide 21 , 90 % yield; thioalkyl 22 , 88 % yield; alkyl 23 , 91 % yield) are tolerated without incident. Using an isophorone‐derived substrate bearing a gem ‐dialkyl substituent on the cyclohexane ring does not affect the reaction significantly, and the product 24 an be isolated in 95 % yield. Variation in the β‐position of the cyclohexenone is also possible: ethyl 25 (93 % yield) and isopropyl 26 (80 % yield; 15:1 d.r.)…”

Section: Methodsmentioning

confidence: 99%

Visible Light Photocatalysis of 6π Heterocyclization

et al. 2017

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Photo-mediated 6p cyclization is avaluable method for the formation of fused heterocyclic systems.H ere we demonstrate that irradiation of cyclic 2-aryloxyketones with blue LED light in the presence of an Ir III complex leads to efficient and high yielding arylation across ap anoply of substrates by energy transfer.2 -Arylthioketones and 2-arylaminoketones also cyclizee ffectively under these conditions. Quantum calculation demonstrates that the reaction proceeds via conrotatory ring closure in the triplet excited state. Subsequent suprafacial 1,4-hydrogen shift and epimerization leads to the observed cis-fused products.

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Section: Methodsmentioning

confidence: 99%

Visible Light Photocatalysis of 6π Heterocyclization

et al. 2017

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“…Prerequisite for this dual catalysis approach are the presence of a Lewis basic coordination site in the substrate and a decrease of the triplet energy upon coordination. The concept was applied to the [6π] photocyclization of 2-aryloxycyclohex-2-enones 86 , which, after a 1,4-hydrogen shift, leads to products 88 (Scheme ). Preliminary studies on this reaction relied on the preferential excitation of a Lewis acid-substrate complex due to a bathochromic absorption shift upon complexation of 86 with Cu(ClO 4 ) 2 ·6H 2 O.…”

Section: Othersmentioning

confidence: 99%

Enantioselective Photochemical Reactions Enabled by Triplet Energy Transfer

et al. 2021

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For molecules with a singlet ground state, the population of triplet states is mainly possible (a) by direct excitation and subsequent intersystem crossing or (b) by energy transfer from an appropriate sensitizer. The latter scenario enables a catalytic photochemical reaction in which the sensitizer adopts the role of a catalyst undergoing several cycles of photon absorption and subsequent energy transfer to the substrate. If the product molecule of a triplet-sensitized process is chiral, this process can proceed enantioselectively upon judicious choice of a chiral triplet sensitizer. An enantioselective reaction can also occur in a dual catalytic approach in which, apart from an achiral sensitizer, a second chiral catalyst activates the substrate toward sensitization. Although the idea of enantioselective photochemical reactions via triplet intermediates has been pursued for more than 50 years, notable selectivities exceeding 90% enantiomeric excess (ee) have only been realized in the past decade. This review attempts to provide a comprehensive survey on the various photochemical reactions which were rendered enantioselective by triplet sensitization.

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“…Photocyclization reactions constitute an important class of transformations with demonstrated application in complex molecule synthesis . Pioneering work by Schultz and Chapman developed the 6π photocyclization manifold from its origins in the excited state electrocyclization of stilbene into a useful class of reactions for the synthesis of aliphatic heterocycles . In spite of the synthetic potential of 6π photocyclization reactions, the necessity for high-energy UV irradiation to achieve excitation of typical chromophores has meant their broader application in synthesis remains limited.…”

Section: Introductionmentioning

confidence: 99%

“…Chromophore activation using chiral Lewis acid complexes has emerged as a viable strategy to induce enantioselectivity in photochemical reactions. In this approach, coordination of a Lewis acid to the reaction substrate results in a bathochromic shift in the UV/vis absorption, thereby facilitating selective excitation within the chiral environment and minimizing racemic background reactivity arising from direct excitation of the reaction substrate. , In the 6π arena, the Bach group applied a chromophore activation strategy to the enantioselective catalysis of Schultz’s α-aryloxyenone photocyclization (Figure a) . Yoon has demonstrated that highly enantioselective [2+2] cycloadditions are possible via a related strategy involving dual Lewis acid and photocatalysis to lower the triplet energy of a coordinated substrate (Figure b) .…”

Section: Introductionmentioning

confidence: 99%

Catalytic Enantioselective 6π Photocyclization of Acrylanilides

et al. 2022

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Controlling absolute stereochemistry in catalytic photochemical reactions is generally challenging owing to high rates of background reactivity. Successful strategies broadly rely on selective excitation of the reaction substrate when associated with a chiral catalyst. Recent studies have demonstrated that chiral Lewis acid complexes can enable selective energy transfer from a photosensitizer to facilitate enantioselective triplet state reactions. Here, we apply this approach to the enantioselective catalysis of a 6π photocyclization through the design of an iridium photosensitizer optimized to undergo energy transfer to a reaction substrate only in the presence of a chiral Lewis acid complex. Among a group of iridium(III) sensitizers, enantioselectivity and yield closely correlate with photocatalyst triplet energy within a narrow window enabled by a modest reduction in substrate triplet energy upon binding a scandium/ligand complex. These results demonstrate that photocatalyst tuning offers a means to suppress background reactivity and improve enantioselectivity in photochemical reactions.

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Heteroatom directed photoarylation. Photochemistry of aryloxyenones

Abstract: References and Notes(1) (a) Fellow of the Alfred P. Sloan Foundation; (b) University Fellow, Rutgers University.

Cited by 25 publications

References 0 publications

Visible Light Photocatalysis of 6π Heterocyclization

Visible Light Photocatalysis of 6π Heterocyclization

Enantioselective Photochemical Reactions Enabled by Triplet Energy Transfer

Catalytic Enantioselective 6π Photocyclization of Acrylanilides

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