Photochemical [2+2]-cycloaddition of cyclic α,β-enones to monosubstitüted acetylenes

Serebryakov, É. P.; Margaryan, A. Kh.

doi:10.1016/0040-4020(79)85011-5

Cited by 15 publications

(3 citation statements)

References 24 publications

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“…Initially, this cycloaddition was assumed to occur through the interaction of a ( n ,π*) excited state of the enone, pressumably a triplet, with the alkene to produce a π-complex or exciplex. The dipole interactions between the polarized enone excited state and the olefin would govern the reaction regiochemistry according to the Corey−de Mayo exciplex mechanism, 5a,7a, thus favoring the formation of some 1,4-biradical intermediates over others. This hypothesis relied on the observation that head-to-tail (HT) adducts were predominant in the cycloadditions of electron-donating olefins to cyclohexenone or cyclopentenone, while head-to-head (HH) adducts were major regioisomers in the reactions with electron-deficient olefins.…”

Section: Introductionmentioning

confidence: 99%

[2 + 2]-Photocycloaddition of 1,1-Diethoxyethylene to Chiral Polyfunctional 2-Cyclohexenones. Regioselectivity and π-Facial Discrimination

et al. 2004

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The photochemical [2 + 2]-cycloadditions of 1,1-diethoxyethylene to chiral polyfunctional 2-cyclohexenones have been carried out leading to the production of highly constrained unusual alpha-amino acids with excellent regioselectivity and satisfactory yields. Theoretical calculations have been done to rationalize the observed regio- and diastereoselectivity and show that regiochemistry is determined by the relative rate of formation of the 1,4-biradical intermediates and not by the stability of these species.

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Section: Introductionmentioning

confidence: 99%

[2 + 2]-Photocycloaddition of 1,1-Diethoxyethylene to Chiral Polyfunctional 2-Cyclohexenones. Regioselectivity and π-Facial Discrimination

et al. 2004

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“…We also engaged more complex cyclobutene substrates that are readily formed by the cascade 6πelectrocyclization/Diels−Alder cycloaddition of cyclooctate- a Conditions: substrate (0.185 mmol), benzaldehyde (5.0 equiv), trifluoroacetic acid (2.0 equiv), and catalyst 3 (1.0 equiv. or 20 mol %) were heated to 80 °C in a sealed vial for 15 h. In the cases where solid substrates were used (17)(18)(19), 0.1 mL chloroform was added. Yields were determined on purified products.…”

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confidence: 99%

“…Meanwhile, 1-alkylcyclopentenes have been subject to ROCOM via Lewis acid catalysis to generate δ,ε-unsaturated ketones, albeit in modest yields. Another ring system for which the development of a ROCOM procedure would be highly desirable includes cyclobutenes 1 (Figure C), which can be assembled in short order via several synthetic strategies. − Notably, the γ,δ-unsaturated aldehyde products 4 resulting from cyclobutene ROCOM are formal Claisen rearrangement products, the value of which has been extensively validated, particularly through numerous total synthesis campaigns. − Despite more than a century of work on this venerable reaction, many Claisen rearrangements remain challenging to execute due to the difficulty of preparing the allyl-vinyl ether substrate . In this regard, cyclobutene ROCOM would offer a potentially valuable alternative entry to these products.…”

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confidence: 99%

Ring-Opening Carbonyl-Olefin Metathesis of Cyclobutenes

Holl

Lambert

2022

ACS Catal.

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The ring-opening carbonyl-olefin metathesis of cyclobutenes to furnish γ,δ-unsaturated aldehydesformal Claisen rearrangement productsis reported. The bistrifluoroacetic acid salt of 2,3-diazabicyclo[2.2.2]octane promotes these reactions efficiently with a variety of cyclobutenes and aldehydes, including aliphatic, α,β-unsaturated, aryl, and heteroaryl aldehydes. Catalytic reactions are also demonstrated.

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Enone Olefin [2 + 2] Photochemical Cycloadditions

Crimmins

Reinhold

1993

Organic Reactions

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The photochemical [2 + 2] cycloaddition reaction of alkenes to enones, the light‐induced cycloaddition of an excited state enone to a ground state alkene to produce a cyclobutane, is a highly useful reaction in organic synthesis since two new carbon–carbon bonds are formed and a maximum of four new stereogenic centers are introduced into the molecule in the process. The first [2 + 2] photocycloaddition reaction was reported by Ciamician in 1908 when he observed the formation of carvone camphor on exposure of carvone to sunlight for one year. After confirmation of this finding in the late 1950s numerous investigators immediately recognized the value of the reaction for the rapid construction of complex molecular frameworks. The photocycloaddition of a series of Diels–Alder adducts of various dienes and benzoquinones to efficiently produce complex caged structures was subsequently carried out. This included the cycloaddition of a diketone to form a diketone. Meanwhile, a similar photochemical cycloaddition of an enone was utilized in a synthesis of the platonic solid cubane. Shortly thereafter investigations of the intermolecular reaction were initiated through a study of the dimerization of cyclopentenone and the photocycloaddition of cyclopentenone to cyclopentene. Further investigation of the various synthetic and mechanistic aspects of the photocycloaddition resulted in several total syntheses, including caryophyllene and bourbonene, as well as a proposed mechanistic rationale for the reaction. As a result of this pioneering work, largely by Eaton, Corey, and De Mayo, numerous natural and nonnatural products have been prepared by synthetic routes which have a [2 + 2] photocycloaddition as a crucial step in their synthesis. Through further refining over the last 15–20 years, the photocycloaddition reaction has become recognized as an important transformation in the repertoire of the synthetic organic chemist. Both the intermolecular and intramolecular versions of the reaction have been extensively studied. The intramolecular photocycloaddition, like the intramolecular variation of many reactions, has been the subject of much recent work. It is generally thought to be more predictable with regard to regiochemical and stereochemical control, but as will be seen from many of the examples in this chapter, the intermolecular reaction can be highly selective and predictable if the proper reaction participants and conditions are chosen. This chapter reviews the literature on the enone olefin [2 + 2] photocycloaddition since its discovery. Because of the volume of work in the field, there will undoubtedly be some omissions. Examples of all the major types of enone alkene photocycloadditions have been included so that the reader can get a sense of the historical evolution and the current state of the art. Both the inter molecular and the intra molecular variants of this reaction are treated in this chapter. The reader is also referred to a number of excellent reviews on the inter molecular reaction, the intra molecular reaction, and complete treatments which have appeared.

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Photochemical [2+2]-cycloaddition of cyclic α,β-enones to monosubstitüted acetylenes

Cited by 15 publications

References 24 publications

[2 + 2]-Photocycloaddition of 1,1-Diethoxyethylene to Chiral Polyfunctional 2-Cyclohexenones. Regioselectivity and π-Facial Discrimination

[2 + 2]-Photocycloaddition of 1,1-Diethoxyethylene to Chiral Polyfunctional 2-Cyclohexenones. Regioselectivity and π-Facial Discrimination

Ring-Opening Carbonyl-Olefin Metathesis of Cyclobutenes

Enone Olefin [2 + 2] Photochemical Cycloadditions

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