Efficient Helicene Synthesis: Friedel–Crafts‐type Cyclization of 1,1‐Difluoro‐1‐alkenes

Ichikawa, Junji; Misaki, Yohji; Kudo, Takao; Umezaki, Satoshi

doi:10.1002/anie.200801396

Cited by 160 publications

(48 citation statements)

References 46 publications

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“…Subsequent alkaline saponification of (P,S)-11a and (M,S)-11a afforded enantiomerically pure (P)-1a (99 %) and (M)-1a (98 %). Furthermore, transformation of the tetrahydro-[6]helicene skeleton of 11a into the fully aromatic [6]helicene skeleton was achieved with triphenylmethylium tetrafluoroborate (Ph 3 CBF 4 ) [9,15] (17) -[6]helicenols 1a and 1b in nonracemic forms efficiently. The prepared compounds 1a and 1b were identified by NMR spectroscopy and mass spectrometry.…”

Section: Scheme 2 Synthesis Of Triynementioning

confidence: 99%

Nickel‐Catalyzed Construction of Chiral 1‐[6]Helicenols and Application in the Synthesis of [6]Helicene‐Based Phosphinite Ligands

et al. 2016

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Two 1‐[6]helicenol derivatives were synthesized by Ni‐catalyzed [2+2+2] cycloaddition on a multigram scale. Both enantiomers of the 1‐[6]helicenols could be efficiently prepared by simple optical resolution. As a synthetic application of helically chiral 1‐[6]helicenols, a novel class of [6]helicene‐based phosphinites was developed; these compounds represent the first examples of helically chiral phosphinite ligands. Up to 90 % ee was obtained for the Pd‐catalyzed asymmetric allylic alkylation reaction.

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Section: Scheme 2 Synthesis Of Triynementioning

confidence: 99%

Nickel‐Catalyzed Construction of Chiral 1‐[6]Helicenols and Application in the Synthesis of [6]Helicene‐Based Phosphinite Ligands

et al. 2016

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“…[4] In both biological and synthetic systems, this reactivity derives from the two sigma-withdrawing fluorine atoms that activate the alkene at the alpha position for attack by nucleophiles. This fundamental reactivity enables the gem-difluoroalkenes to serve as intermediates for a broad spectrum of synthetic transformations (e. g. coupling reaction, condensation, addition-elimination, polymerization, hydrodefluorination) that deliver diverse functional groups, including fluorinated alkene, indole, ester, carboxylic acid, [5] methylene, cyclopropane, and methyl groups. [6] gem-Difluoroalkenes also serve as synthetic precursors for the preparation of polymers.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Transition Metal‐Catalyzed Functionalization of gem‐Difluoroalkenes

Koley

Altman

2020

Israel Journal of Chemistry

113

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gem-Difluorinated alkenes are readily accessible building blocks that can undergo functionalization to provide a broad spectrum of fluorinated and non-fluorinated products. Herein, we review recent (since 2017) transition metalcatalyzed transformations of these specialized alkenes and summarize general reactivity patterns of these reactions. Many transition metal-catalyzed reactions undergo net CÀ F bond functionalization reactions to deliver monofluorinated products. These reactions typically proceed through β-fluoroalkylmetal intermediates that readily eliminate a βfluoride to deliver monofluoroalkene products. A second series of reactions exploit coinage metal fluorides to add F À to the gem-difluorinated alkene, and further functionalization delivers trifluoromethyl-containing products. In stark contrast, few transition metal-catalyzed reactions proceed in net "fluorine-retentive processes" to deliver difluoromethylenebased products. Reactions Proceeding via β-Fluoride Eliminationgem-Difluoroalkenes react with a variety of transition metalbased catalyst systems (e. g. Cu, Co, Mn, Pd, Ni, Ru, Rh) in net CÀ F functionalization reactions. These reactions typically proceed through a β-fluoroalkylmetal intermediate that readily undergoes β-fluoride elimination to form a new alkene based product (Scheme 1). At first, reaction of a substrate-ligated complex (1) to the gem-difluoroalkene 2, proceeds through a four-membered transition state 3 to generate the intermediate 4. This process involves the matching of the anionic ligand (Y) with the cationic α,α-difluorinated position of the alkene, which generates an intermediate metalalkyl bearnig two βfluoride atoms. Subsequent β-fluoride elimination generates [a] S.Scheme 3. Plausible mechanism for defluoroborylation of aliphatic gem-difluoroalkenes. Scheme 4. CÀ F Bond borylation of gem-difluoroalkenes. Scheme 5. Copper-catalyzed trans-selective monodefluoroborylation of various gem-difluoroalkenes. Scheme 6. CÀ F Bond borylation of gem-difluoroalkenes. Scheme 7. Copper-catalyzed tunable multi-borylation reactions of gem-difluoroalkenes. In parentheses the ratio of 22, 23 and 24 is reported. Scheme 8. Stereoselective defluorinative borylation and silylation of gem-difluoroalkenes. Scheme 9. a) Synthesis of fluorinated vinylsilanes from gem-difluoro/ polyfluoroalkenes. b) Cross-coupling reaction of 29 b and iodobenzene. Scheme 10. Nickel-catalyzed fluoroalkenylation of unactivated alkylbromides. rr = The regioisomeric ratio of the benzylic fluoroÀ alkenylation product to the other regioisomers. DMA = N,N-Dimethylacetamide. Scheme 14. Iron-catalyzed defluorinative cross-coupling of donor alkenes with gem-difluoroalkenes. Dibm = diisobutyrylmethane. Scheme 15. Nickel-catalyzed reductive aryl monofluoroalkenylation of alkenes. Scheme 16. Plausible mechanism for reductive aryl monofluoroalkenylation of gem-difluoroalkenes. Scheme 17. Nickel-catalyzed hydroalkenylation of alkynes through oxidative cyclization and β-fluoride elimination. Scheme 28. Ruthenium-catalyzed fluoroal...

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“…[1] For example, the unique gem-difluorostyrenes could be used as the precursors of esters/carboxylic acids, [2] monofluoroalkenes [3] and some other functional groups. [5] Meanwhile, organophosphorus compounds are also an important class of functional molecules which play a huge role in biological systems like protein activation, energy metabolism and signal transductions. [5] Meanwhile, organophosphorus compounds are also an important class of functional molecules which play a huge role in biological systems like protein activation, energy metabolism and signal transductions.…”

Section: Introductionmentioning

confidence: 99%

Metal‐Free Access to (E/Z)‐α‐Fluorovinyl Phosphorus Compounds from gem‐Difluorostyrenes

Peng

Zhang

et al. 2019

Eur J Org Chem

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A facile and efficient method for the synthesis of (E/Z)‐α‐fluorovinyl phosphorus compounds from gem‐difluorostyrenes with diphenylphosphine oxide/dialkyl phosphate and DBU at room temperature was developed. A series of 1‐fluorovinyl phosphine oxides/phosphonates were obtained with moderate to excellent yields in these reactions. Additionally, most isomers (E/Z type) of the target compounds could be easily separated and purified by column chromatography.

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Efficient Helicene Synthesis: Friedel–Crafts‐type Cyclization of 1,1‐Difluoro‐1‐alkenes

Cited by 160 publications

References 46 publications

Nickel‐Catalyzed Construction of Chiral 1‐[6]Helicenols and Application in the Synthesis of [6]Helicene‐Based Phosphinite Ligands

Nickel‐Catalyzed Construction of Chiral 1‐[6]Helicenols and Application in the Synthesis of [6]Helicene‐Based Phosphinite Ligands

Recent Advances in Transition Metal‐Catalyzed Functionalization of gem‐Difluoroalkenes

Metal‐Free Access to (E/Z)‐α‐Fluorovinyl Phosphorus Compounds from gem‐Difluorostyrenes

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