Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

Scheidt, Felix; Thiehoff, Christian; Yılmaz, Gülay Can; Meyer, Stephanie; Daniliuc, Constantin G.; Kehr, Gerald; Gilmour, Ryan

doi:10.3762/bjoc.14.88

Cited by 42 publications

(21 citation statements)

References 37 publications

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“…The effects of the HF:amine ratio on Brønsted acid activation and in determining regioselectivity (geminal versus vicinal) is described in Table . The optimisation was initiated using previously reported conditions from this laboratory with commercially available Selectfluor as the terminal oxidant and a mixture of NEt 3 ⋅3 HF and Pyr⋅(HF) x as amine⋅HF sources. This system, which permits careful tuning of the acidity, proved to be instrumental in augmenting both conversion and selectivity.…”

Section: Figurementioning

confidence: 99%

Enantioselective, Catalytic Vicinal Difluorination of Alkenes

et al. 2018

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The enantioselective, catalytic vicinal difluorination of alkenes is reported by II/IIII catalysis using a novel, C2‐symmetric resorcinol derivative. Catalyst turnover via in situ generation of an ArIIIIF2 species is enabled by Selectfluor oxidation and addition of an inexpensive HF–amine complex. The HF:amine ratio employed in this process provides a handle for regioselective orthogonality as a function of Brønsted acidity. Selectivity reversal from the 1,1‐difluorination pathway (geminal) to the desired 1,2‐difluorination (vicinal) is disclosed (>20:1 in both directions). Validation with electron deficient styrenes facilitates generation of chiral bioisosteres of the venerable CF3 unit that is pervasive in drug discovery (20 examples, up to 94:06 e.r.). An achiral variant of the reaction is also presented using p‐TolI (up to >95 % yield).

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Section: Figurementioning

confidence: 99%

Enantioselective, Catalytic Vicinal Difluorination of Alkenes

et al. 2018

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“…Confidence in this approach stemmed from our recent vicinal and geminal difluorination of alkenes [ 26 – 30 ], and contemporaneous studies from the Jacobsen laboratory [ 31 – 34 ], under the auspices of I(I)/I(III) catalysis [ 35 – 37 ]. Moreover, elegant studies by Hara and co-workers have demonstrated that α-fluoroketones could be prepared by exposing silyl enol ethers to stoichiometric p -ToIIF 2 , in the presence of BF 3 ·OEt 2 and NEt 3 /HF 1:2 [ 38 ].…”

Section: Introductionmentioning

confidence: 99%

Fluorohydration of alkynes via I(I)/I(III) catalysis

Neufeld¹,

Daniliuc²,

Gilmour³

2020

Beilstein J. Org. Chem.

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Substrate specificity is ubiquitous in biological catalysis, but less pervasive in the realm of small-molecule catalysis. Herein, we disclose an intriguing example of substrate specificity that was observed whilst exploring catalysis-based routes to generate α-fluoroketones from terminal and internal alkynes under the auspices of I(I)/I(III) catalysis. Utilising p-TolI as an inexpensive organocatalyst with Selectfluor® and amine/HF mixtures, the formation of protected α-fluoroketones from simple alkynes was realised. Whilst the transient p-TolIF2 species generated in situ productively engaged with pentynyl benzoate scaffolds to generate the desired α-fluoroketone motif, augmentation or contraction of the linker suppressed catalysis. The prerequisite for this substructure was established by molecular editing and was complemented with a physical organic investigation of possible determinants.

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“…Later, a synthetic route to 5-fluoromethyl-2-oxazolines from the readily accessible N-allylcarboxamides was developed via iodine(I)/(III) catalysis employing p-iodotoluene (10 mol%) as an organocatalyst and selectfluor as an oxidant. [32] Amine • HF serves as both fluoride source and Brønsted acid activator. The optimal amine/HF ratio (1:4.5) was easily obtained by combining the commercially available triethylamine tris(hydrogenfluoride) (Et 3 N • 3HF) and Olah's reagent (pyridine • HF).…”

Section: Amino- Oxy-or Carbofluorination Of Alkenesmentioning

confidence: 99%

“…Given the importance of fluorine substitution in drug discovery, this strategy provided a rapid entry into an important bioisostere class of bioactive 2-oxazoline scaffolds. [32] Very recently, iodine(I)/(III)-catalyzed direct fluorocyclization of aryl allyl ethers (76) with a simple C2symmetric iodoresorcinol catalyst in combination with selectfluor and amine • HF mixtures was disclosed by Gilmour and coworkers, forming biologically relevant enantio-enriched 3-fluorochromanes (77) with up to 7:93 e.r. value (Scheme 15).…”

Section: Amino- Oxy-or Carbofluorination Of Alkenesmentioning

confidence: 99%

Fluorination and Fluoroalkylation Reactions Mediated by Hypervalent Iodine Reagents

Han

Zhang

2020

Adv Synth Catal

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This review summarizes the progress in the fluorination and fluoroalkylation of electron-rich systems with diverse fluorine (F) and fluoroalkyl (R fn) reagents employing hypervalent iodine compounds as initiators in the last few decades. Because of the strong electrophilicity, high oxidizing properties, low toxicity, air and moisture stability, ready availability, ease of handling, and mild reaction conditions, the hypervalent iodine reagents have been widely utilized in modern organic chemistry. In particular, the use of hypervalent iodine reagents to initiate the CÀ F and CÀ R fn (R fn =CF 2 H, CF 3 , perfluoroalkyl, OCH 2 CF 3 , SCF 3 , SeCF 3 and etc) bond formation has been increasingly developed. In these reactions, hypervalent iodine compounds behave as powerful oxidants or electrophiles and activate the fluorination/fluoroalkylation reagents, the transitionmetal catalysts, or the substrates to in situ form electrophilic or radical intermediates, which subsequently participate in fluorination, difluoromethylation, trifluoromethylation, perfluoroalkylation, trifluoroethoxylation, fluoroalkylthiolation, trifluoromethylselenolation and others under mild conditions. Although great achievements have been made in this area, they are just the initial phase and still require a wide scope for improvement. It is anticipated that this review will draw much attention from the organic chemistry community and inspire more contributions in the development of new hyper-valent-iodine-mediated fluorination and fluoroalkylation reactions.

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Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

Cited by 42 publications

References 37 publications

Enantioselective, Catalytic Vicinal Difluorination of Alkenes

Enantioselective, Catalytic Vicinal Difluorination of Alkenes

Fluorohydration of alkynes via I(I)/I(III) catalysis

Fluorination and Fluoroalkylation Reactions Mediated by Hypervalent Iodine Reagents

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