Synthesis of 6H-Benzo[c]chromene Scaffolds from O-Benzylated Phenols through a C–H Sulfenylation/Radical Cyclization Sequence

Karreman, Steve; Karnbrock, Simon B. H.; Kolle, Sebastian; Golz, Christopher; Alcarazo, Manuel

doi:10.1021/acs.orglett.1c00087

Cited by 22 publications

(48 citation statements)

References 38 publications

(34 reference statements)

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“…To our delight, the proposed transformation took place smoothly and the expected phenanthrenes 14 and 16 were obtained, albeit with moderate yields (Scheme 5 ). [22] …”

Section: Resultsmentioning

confidence: 99%

“…To our delight, the proposed transformation took place smoothly and the expected phenanthrenes 14 and 16 were obtained, albeit with moderate yields (Scheme 5). [22] Synthesis of the 6 a,7-dihydroaporphine scaffold. Finally, we decided to explore whether the just described addition/ cyclisation protocol would be useful for the synthesis of the 6a,7-dihydroaporphine core A, a tetracyclic amine which constitutes the skeleton of dozens of alkaloids such as for example Artabotrine (17), [23] (À )-6a,7-dehydrofloripavidine (18), [24] or Telisatin B (19), [25] among others.…”

Section: Resultsmentioning

confidence: 99%

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Reactivity of 5‐(Alkynyl)dibenzothiophenium Salts: Synthesis of Diynes, Vinyl Sulfones, and Phenanthrenes

et al. 2021

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The reactivity of 5‐(alkynyl)dibenzothiophenium salts 1 is explored in the presence of different nucleophiles, dienes, and under photochemical conditions. Reaction with lithium acetylides affords diynes in moderate yields; while depending on the substitution pattern, the reaction with sulfinates delivers either the alkyne transfer products, alkynyl sulfones, or β‐(sulfonium) vinyl sulfones through addition to the C−C triple bond. Similar behavior is observed when tosylamines are used as nucleophiles. Salts of general formula 1 also react with dienes to render the corresponding Diels‐Alder cycloadducts. The vinyl sulfonium salts obtained by these routes further react with nucleophiles through a Michael addition, dibenzothiophene elimination sequence. Alternatively, they also engage in photoinduced radical cyclizations to produce substituted phenanthrenes. Attempts to use this specific addition/radical cyclization sequence for the construction of the 6a,7‐dehydroaporphine skeleton present in several families of alkaloids are also described.

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“…To our delight, the proposed transformation took place smoothly and the expected phenanthrenes 14 and 16 were obtained, albeit with moderate yields (Scheme 5 ). [22] …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Reactivity of 5‐(Alkynyl)dibenzothiophenium Salts: Synthesis of Diynes, Vinyl Sulfones, and Phenanthrenes

et al. 2021

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“…The latter is a direct result of the encapsulated metal ions having larger ion sizes than carbon. Comparing the pyramidalization among the ligands (238)(239)(240)(241)(242)(243), one finds a trend with the corresponding effective ionic radii [173,174] of the encapsulated metal ion. Thus, ligands encapsulating highly oxidized [Co 3+ (ls), 241] or low-spin 3d metal ions [Fe 2+ (ls), 239], with small effective ionic radii, have a higher pyramidalization(<295°) than the others [Mg 2+ 238, Co 2+ (hs) 240, Zn 2+ 242, Ru 2+ (ls) 243].…”

Section: Pyramidalizationmentioning

confidence: 97%

“…Apart from this, the released HOTf occasionally causes problems with acid labile functional groups, which can be addressed by the addition of base. [242] The use of cyclic scaffolds like 373 in which two aromatic substituents of the sulfur are bridged offers synthetic advantages in subsequent reactions, when chemoselective transfer of only one particular substituent is required. Therefore, arylthianthrenium or aryldibenzothiophenium salts like 373 are often used in the literature.…”

Section: S-(aryl) Sulfonium Salts -Synthesismentioning

confidence: 99%

“…Scheme 124: Two-step cyclization tool [242] Inspired by the research of Fensterbank, Goddard, Ollivier and co-workers and supported by the publication of Procter (Chapter 4.3.3), our goal was to develop a two-step cyclization tool that formally CꟷH/CꟷH couples two linked arenes. The methodology should therefore consist of a regioselective functionalization step in which an appropriately designed arene is sulfenylated, followed by a subsequent photocatalytic cyclization step, which leads selectively to one cyclized product.…”

Section: Project Iii: Two-step Cyclization Tool Based On Sulfenylatio...mentioning

confidence: 99%

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Tuning the donor properties of bipyridyl-substituted phosphines by metal ion encapsulation & Photocatalytic synthesis of 6H-benzo[c]chromenes from S-aryl sulfonium salts

Karreman¹

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Lewis acid catalysis vs. Brønsted acid catalysisWith the corresponding costs for ligands and noble metals, the question arises why one cannot simply use proton catalysis instead (Brønsted acid catalysis). A proton is after all isolobal to the LAu + and Hg 2+ fragments. An evident difference is the contrasting hardness according to the Pearson concept. [6] Protons are hard Lewis acids, while mentioned metal fragments are soft Lewis acids. This difference leads to the fact that protons often need harsh reaction conditions and are less selective. The softer metal fragments, however, have higher affinity to soft substrates and therefore require less harsh conditions and react in higher selectivity. Besides this evident difference, the use of metal fragments also allows the possibility of stabilizing carbene-like intermediates and to unlock their reactivity. In the case of gold(I), this topic is highly controversial, and resonances of gold carbenes or gold-stabilized carbocations are discussed (→"carbenoid" [6] or "carbene" [11] , Scheme 2). [11,12] Scheme 2: Gold carbene [11] Scheme 14:Chalk-Harrod mechanism [36] The latter mechanism is composed of oxidative addition (I) followed by ligand association (II), insertion (III) and reductive elimination (IV). As a side reaction, mainly β-hydride elimination is present. Because of its ability to activate inert bonds, platinum(II) is also used in the activation of methane, which represents a classic example of CꟷH activation (Shilov system). [37] Methanol and chloromethane can Scheme 20: Oxidation of phosphines to phosphine selenides [55] Since the J-coupling constant contains information about the electronic environment, bonding situation and hybridization of 31 P (I = ½) and 77 Se (I = ½) via the Fermi contact interaction, it is also strongly influenced by the polarization of the PꟷSe bond. If electron pushing substituents are chosen on the phosphorus, the coupling constant 1 JPSe decreases, while electron withdrawing substituents result in high coupling constants. In other words, the coupling constant decreases as the basicity of the corresponding unoxidized phosphine increases (Scheme 21).

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Hypervalent Iodine and Sulfur‐Mediated CH Functionalization

Cai

Zhao

2022

Handbook of CH-Functionalization

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Hypervalent main group nonmetallic elements, such as iodine and sulfur, have attracted increasing attention owing to their unique reactivities. The facilely interconvertible valencies sometimes render these nonmetallic elements chemical behaviors analogs to transition metals, allowing diverse CH functionalizations to proceed in a green manner. Since their discovery, hypervalent iodine reagents have played a pivotal role in synthetic organic chemistry. Besides their usage as selective oxidants, hypervalent iodine reagents readily participate in single‐electron transfer processes to produce radical cation intermediates, enabling a variety of oxidative carbon–carbon and carbon–heteroatom bond formations. Direct CH functionalization of arenes, alkenes, and alkynes gives rapid access to aryl iodonium salts, which are easily transformed into other functionalities. Similarly, site‐selective CH thianthrenation proceeds smoothly upon suitable activation of sulfoxide reagents. The superior leaving ability and redox properties make the thianthrene moiety an ideal synthetic handle for structural diversifications via transition‐metal and photoredox catalysis. In this article, we focus on the hypervalent iodine and sulfur‐mediated CH functionalizations and describe their applications in carbon–carbon and carbon–heteroatom bond‐forming reactions. The rearrangement‐based CH functionalization will be briefly introduced where possible.

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Synthesis of 6H-Benzo[c]chromene Scaffolds from O-Benzylated Phenols through a C–H Sulfenylation/Radical Cyclization Sequence

Cited by 22 publications

References 38 publications

Reactivity of 5‐(Alkynyl)dibenzothiophenium Salts: Synthesis of Diynes, Vinyl Sulfones, and Phenanthrenes

Reactivity of 5‐(Alkynyl)dibenzothiophenium Salts: Synthesis of Diynes, Vinyl Sulfones, and Phenanthrenes

Tuning the donor properties of bipyridyl-substituted phosphines by metal ion encapsulation & Photocatalytic synthesis of 6H-benzo[c]chromenes from S-aryl sulfonium salts

Hypervalent Iodine and Sulfur‐Mediated CH Functionalization

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