
==== Front
Beilstein J Org Chem
Beilstein J Org Chem
Beilstein Journal of Organic Chemistry
1860-5397
Beilstein-Institut Trakehner Str. 7-9, 60487 Frankfurt am Main, Germany

10.3762/bjoc.20.197
Full Research Paper
Chemistry
Organic Chemistry
Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes
Thai Phong https://orcid.org/0000-0001-6283-9344
1
Patel Lauv 1
Manna Diyasha https://orcid.org/0009-0009-2647-0776
1
Powers David C https://orcid.org/0000-0003-3717-2001
powers@chem.tamu.edu
1
Gulder Tanja Guest Editor
1 Department of Chemistry, Texas A&M University, College Station TX, 77843, USA https://ror.org/01f5ytq51 https://www.isni.org/isni/0000000446872082
2024
11 9 2024
20 23052312
10.3762/bjoc.20.19723 5 2024
5 9 2024
Copyright © 2024, Thai et al.
2024
Thai et al.
https://creativecommons.org/licenses/by/4.0/ This is an open access article licensed under the terms of the Beilstein-Institut Open Access License Agreement (https://www.beilstein-journals.org/bjoc/terms/terms), which is identical to the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0). The reuse of material under this license requires that the author(s), source and license are credited. Third-party material in this article could be subject to other licenses (typically indicated in the credit line), and in this case, users are required to obtain permission from the license holder to reuse the material.
Iminoiodinanes comprise a class of hypervalent iodine reagents that is often encountered in nitrogen-group transfer (NGT) catalysis. In general, transition metal catalysts are required to effect efficient NGT to unactivated olefins because iminoiodinanes are insufficiently electrophilic to engage in direct aziridination chemistry. Here, we demonstrate that 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) activates N-arylsulfonamide-derived iminoiodinanes for the metal-free aziridination of unactivated olefins. 1H NMR and cyclic voltammetry (CV) studies indicate that hydrogen-bonding between HFIP and the iminoiodinane generates an oxidant capable of direct NGT to unactivated olefins. Stereochemical scrambling during aziridination of 1,2-disubstituted olefins is observed and interpreted as evidence that aziridination proceeds via a carbocation intermediate that subsequently cyclizes. These results demonstrate a simple method for activating iminoiodinane reagents, provide analysis of the extent of activation achieved by H-bonding, and indicate the potential for chemical non-innocence of fluorinated alcohol solvents in NGT catalysis.

aziridination
electrochemistry
H-bond activation
hypervalent iodine
nitrene transfer
Welch Foundation http://dx.doi.org/10.13039/100000928 A-1907 National Science Foundation http://dx.doi.org/10.13039/100000001 1848135 The authors acknowledge the Welch Foundation (A-1907) and the National Science Foundation (CAREER 1848135) for financial support.All costs related to the publication of this open access article were entirely funded by the Beilstein-Institut.

This article is part of the thematic issue "Hypervalent halogen chemistry".
==== Body
pmcIntroduction

Hypervalent iodine reagents find widespread application in selective oxidation chemistry due to the combination of synthetically tunable iodine-centered electrophilicity and the diversity of substrate functionalization mechanisms that can be accessed [1–2]. Large families of iodine(III)- and iodine(V)-based reagents have been developed – including iodobenzene diacetate (PhI(OAc)2, PIDA), Koser’s reagent (PhI(OH)OTs), Zhdankin’s reagent (C6H4(o-COO)IN3, ABX), and Dess–Martin periodinane (DMP) – and find application in an array of synthetically important transformations including olefin difunctionalization, carbonyl desaturation, alcohol oxidation, and C–H functionalization [3–4]. Iminoiodinanes (ArI=NR) are a subclass of hypervalent iodine reagents that function as nitrene equivalents in synthesis [5–6]. The direct reaction of iminoiodinanes with olefins, which could be envisioned to give rise to aziridines directly, is typically not observed and thus families of transition metal catalysts or photochemical procedures have been developed to enable this transformation [7–9].

The reactivity of hypervalent iodine reagents can be enhanced via Lewis acid catalysis [10]. For example, PIDA becomes a stronger oxidant upon coordination of BF3·OEt2, enabling chemistry that was not available in the absence of Lewis acid activation (Scheme 1a) [11–12]. A variety of Lewis acid activators have been reported [13–22] in an array of group-transfer reactions, including trifluoromethylation, cyanation, and fluorination. Brønsted acid activation has also been described in some group-transfer schemes [23–25], and in particular, fluorinated alcohol solvents, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), have been reported to enhance hypervalent iodine reactivity by providing a H-bonding solvent cluster that enhances the electrophilicity of the iodine center [26–27]. Despite the prevalence of acid-activation in promoting carbon [28], oxygen [29–30], sulfur [31], chlorine [32], and fluorine [33] transfer reactions of hypervalent iodine compounds, these strategies have not been applied to activation of iminoiodinanes for nitrene transfer chemistry.

Scheme 1 a) Lewis acid activation of hypervalent iodine reagents can enhance the reactivity of these reagents. b) Charge-tagged iminoiodinanes display enhanced reactivity in aziridination reactions with unactivated olefins (ref. [34]). c) Here, we demonstrate that H-bonding between fluorinated alcohol solvents and iminoiodinanes can enable direct metal-free aziridination of unactivated olefins with simple iminoiodinanes.

We recently developed a metal-free aziridination of unactivated olefins via the intermediacy of an N-pyridinium iminoiodinane (Scheme 1b) [34]. We rationalized the enhanced reactivity towards olefin aziridination as a result of charge-enhanced iodine-centered electrophilicity arising from the cationic N-pyridinium substituent. Based on those observations, we reasoned that similarly enhanced reactivity might be accessed by Lewis acid or H-bond activated iminoiodinanes. Here, we describe the HFIP-promoted aziridination of unactivated olefins with N-sulfonyl iminoiodinane reagents, which are among the most frequently encountered iminoiodinanes in NGT catalysis (Scheme 1c). This simple procedure afforded the formal transfer of various nitrogen groups, including those derived from complex amines, and is complementary to other metal-free aziridinations of unactivated olefins [35–39].

Results and Discussion

Treatment of cyclohexene (1a) with a stoichiometric amount of simple iminoiodinane such as PhINTs (2a) in CH2Cl2 resulted in <10% conversion to the corresponding N-sulfonylaziridine 3a, which is consistent with the previously reported need for transition metal catalysts to promote nitrene transfer catalysis (Table 1, entry 1) [40–41]. In contrast, combination of PhINTs (2.0 equiv) with 1a in HFIP afforded 3a in 67% NMR yield (Table 1, entry 2). Lowering the loading of iminoiodinane 2a to 1.5 or 1.0 equivalents decreased the reaction yield to 28% and 22%, respectively (Table 1, entries 3 and 4). Increasing the reaction temperature negatively affected the efficiency of aziridination: Reactions performed at 30 or 50 °C afforded 3a in 50% and 43% yield, respectively (Table 1, entries 5 and 6). Replacing HFIP with 2,2,2-trifluoroethanol (TFE), which is also a commonly encountered fluorinated alcohol solvent, resulted in a 16% yield of 3a (Table 1, entry 7). Performing aziridination with 10 equivalents of HFIP in CH2Cl2 resulted in a 38% yield (Table 1, entry 8). The aziridine product 3a was not observed when other Lewis or Brønsted acids, such as BF3·Et2O, TfOH, or Zn(OTf)2, were employed in CH2Cl2 (Table 1, entry 9). Attempts to generate 2a in situ using 1 equivalent of TsNH2 (4) in combination with 1 or 2 equivalents of PhIO (5) resulted in aziridination yields of 19% and 27%, respectively (Table 1, entries 10 and 11). Finally, exclusion of ambient light had no impact of the aziridination of 1a with PhINTs (Table 1, entry 12) [42–43].

Table 1 Optimization of HFIP-promoted aziridination of cyclohexene (1a). Conditions: 0.20 mmol 1a, 0.40 mmol PhINTs 2a, 1.0 mL HFIP, N2 atmosphere, 20 °C, 16 h. Yield was determined via 1H NMR using triethyl 1,3,5-benzenetricarboxylate as internal standard.

	
	
Entry	Deviation from standard conditions	Yield (%)	
	
1	CH2Cl2	<10%	
2	none	67	
3	1.5 equiv PhINTs	28	
4	1.0 equiv PhINTs	22	
5	30 °C	50	
6	50 °C	43	
7	TFE	16	
8	10 equiv HFIP in CH2Cl2	38	
9	5 equiv BF3·Et2O, TfOH, or Zn(OTf)2 in CH2Cl2,	0	
10	1 equiv 4 and 1 equiv 5 instead of 2a	19	
11	1 equiv 4 and 2 equiv 5 instead of 2a	27	
12	no ambient light	64	

With metal-free aziridination conditions in hand, we explored the scope and limitations of the HFIP-promoted aziridination of unactivated olefins (Scheme 2). For cyclic substrates, aziridination of cyclopentene, cyclohexene, and cycloheptene afforded the corresponding aziridines in modest to high isolated yields: 3b (80%), 3a (46%), and 3c (36%), respectively. Acyclic olefin 1-hexene underwent aziridination to 3d in 79% yield (reaction performed at 50 °C); aziridination of vinylcyclohexane proceeded in 67% yield of 3e. Allylbenzene engaged in aziridination to deliver 3f in 53% yield, while homoallylbenzene and pent-4-en-1-ylbenzene underwent aziridination in yields of 54% (3g) and 26% (3h), respectively. The procedure was compatible with various commonly encountered functional groups, such as chloride (3i), bromide (3j), and benzoyl (3k). Noticeably, an unprotected alcohol is tolerated in our procedure, with product 3l delivered at 50% NMR yield; 3l is sensitive to column chromatography, and thus aziridine-opening to a cyclic ether was observed (31% isolated yield) during purification. Aziridination of cis- or trans-4-octene afforded aziridine 3m as a 1.3:1.0 trans/cis mixture in 72% and 64% yield, respectively. While many styrene derivatives polymerize in HFIP [44], 1,2-disubstituted styrene derivatives were sufficiently stable to engage in the developed aziridination reaction, with cis- or trans-β-methylstyrene 1n furnishing aziridine 3n as diastereomeric mixtures with comparable yields of 38% (1.0:2.0 trans/cis, from cis-1n) and 35% (1.7:1.0 trans/cis, from trans-1n). Olefins containing N-heteroaromatics such as phthalimide and pyridine underwent aziridination to give 3o (32% yield) and 3p (26% yield). Similarly, 1,4-cyclohexadiene was compatible in this procedure, giving product 3q in 21% yield (see Supporting Information File 1, Figure S1 for other challenging substrates). Finally, ibuprofen-derived olefin 1r underwent aziridination to afford 3r in 31% yield. Overall, these results highlight the efficacy of a simple activation protocol and the generality of H-bond activation of iminoiodinanes for direct aziridination, albeit with modest efficiency for some substrates.

Scheme 2 Scope and limitations of HFIP-promoted direct aziridination with iminoiodinane reagents. Conditions: 0.20 mmol 1, 0.40 mmol 2a, 1.0 mL HFIP, N2 atmosphere. a) 20 °C for 16 h, b) 50 °C for 16 h, c) 50 °C for 48 h, d) NMR yield, e) 1.2 equiv PhINTs was used, and f) 4.0 equiv of PhINTs at 20 °C for 48 h.

The impact of the iminoiodinane structure on the efficiency of HFIP-promoted direct aziridination was next investigated (Scheme 3). For this purpose, cyclopentene was selected as it underwent efficient aziridination with PhINTs. A family of iminoiodinanes 2 was synthesized from PIDA and the corresponding sulfonamide derivative. Reaction of phenylsulfonamide-derived iminoiodinane with cyclopentene afforded N-phenylsulfonylaziridine 6b in 45% yield, while N-(p-trifluoromethylsulfonyl)aziridine 6c was furnished in 47% yield. Similarly, 2,6-difluorosulfonyl-substituted iminoiodinane 2d afforded aziridine 6d in 52% yield. The aziridination procedure was tolerant of heterocyclic substituents on the iminoiodinane, N-(5-methylpyridin-2-ylsulfonyl)aziridine 6e could be obtained in 46% yield. The N-Tces group (Tces = trichloroethylsulfamate) could also be transferred to afford 6f in 39% yield. Finally, the iminoiodinane derived from celecoxib (2i) could be used to transfer this drug moiety to furnish aziridine 6i in 46% yield. In general, the efficiency of aziridination correlates with the stability of the relevant iminoiodinane reagent, with higher yields attributed to more electron-rich sulfonamide substitution such as 2a. Relatively electron-deficient iminoiodinanes are less efficient but are also more prone to decomposition (see Supporting Information File 1, Figure S2 for challenging iminoiodinanes). In situ preparation of the iminoiodinane intermediates is possible, and for those reagents that undergo facile decomposition, aziridination is more efficient using these conditions (yields for in situ-generated iminoiodinanes are in parentheses in Scheme 3, with N-o-methyl (6g) and N-p-methoxysulfonyl (6h) aziridines obtained each in 22% yield; the drug topiramate could also be transferred to furnish aziridine 6j in 11% yield).

Scheme 3 Scope of nitrogen group transfer in the aziridination of aliphatic olefins. Conditions using synthesized iminoiodinane: 0.20 mmol cyclopentene (1b), 0.40 mmol iminoiodinane 2, 1.0 mL HFIP, N2 atmosphere. Conditions using in situ-generated iminoiodinane: 0.20 mmol cyclopentene (1b), 0.20 mmol sulfonamide, 0.40 mmol iodosylbenzene (PhIO), 1.0 mL HFIP, N2 atmosphere. a) 20 °C for 16 h, b) 40 °C for 16 h.

We carried out a series of experiments to clarify the origin of the observed reactivity enhancement of N-arylsulfonyliminoiodinanes in the presence of HFIP (Scheme 4). First, 1H NMR was employed to examine the interaction between HFIP and iminoiodinane 2c in CD3CN (compound 2c was chosen over 2a due to its increased solubility in nonprotic solvents). In a sample of 2c with 4 equivalents of HFIP, a broad signal for O–H proton of HFIP was observed at 5.52 ppm with a FWHM = 56.6 Hz (Scheme 4a). This resonance was broader and more downfield than that of free HFIP in CD3CN (5.41 ppm with FWHM = 5.0 Hz), suggesting a hydrogen bonding interaction between HFIP and 2c, and similar observations were also reported for the hydrogen bonding between HFIP and PIDA [30,33]. During this experiment, a small amount of hydrolysis product 4-(trifluoromethyl)benzenesulfonamide was also observed (1.2 mM, signals at 8.0, 7.9, and 5.86 ppm), but this compound did not greatly contribute to the broadening of O–H proton signal of HFIP as a separate 4.0 mM sample of the sulfonamide resulted in O–H proton signal of HFIP being at 5.64 ppm with FWHM = 11.3 Hz. Second, to evaluate the impact of HFIP on the redox chemistry of PhINTs, we collected cyclic voltammograms (CVs) of iminoiodinane 2c in MeCN in the presence of varying HFIP increments (Scheme 4b). The CV of 25 µL HFIP in MeCN showed no electrochemical events between −2.0–0 V. The CV of 2c in the absence of HFIP showed a reductive current (ip = −0.80 mA) at peak potential (Epr) of –1.72 V vs Fc+/Fc. Upon addition of 5.0 µL of HFIP (1.2 equiv with respect to 2c), the current increased to −1.22 mA, signaling the binding of HFIP to 2c enhanced the electron transfer kinetics between the hypervalent iodine reagent and the electrode [45]. Further additions of HFIP further increased the current response and shifted the peak potential, with 10 µL and 15 µL of HFIP showing responses with Epr at −1.55 V and −1.52 V, respectively. The titration showed a saturation point at 25 µL of HFIP (6.0 equiv with respect to 2c), at which the CV of 2c showed an Epr = –1.47 V and –1.52 mA current. Overall, the addition of HFIP results in a 250 mV shift in the reduction of 2c. The increased facility of reduction is consistent with H-bonding between HFIP and 2c, which results in a more potent oxidant and gives rise to the observed HFIP-promoted olefin aziridination chemistry.

Scheme 4 a) The broadening of the hydroxide proton (denoted by asterisk *) of HFIP in the presence of iminoiodinane 2c suggesting hydrogen bonding observed in 1H NMR spectra (CD3CN) of: 8.0 mM 2c with no HFIP (blue line), 8.0 mM 2c with 32 mM HFIP (green line), 4.0 mM of 4-(trifluoromethyl)benzenesulfonamide with 32 mM HFIP (purple line), only 32 mM HFIP (red line). b) Cyclic voltammogram of iminoiodinane 2c (8.0 mM) with varying amounts of HFIP in 5.0 mL solution of MeCN (0.10 M TBABF4) under N2 atmosphere: 2c with no HFIP (black line); 2c with 5, 10, 15 µL HFIP (grey line); 2c with 25 µL HFIP (red line); only 25 µL (blue line). c) Diastereomeric mixtures of aziridines are obtained from aziridination reactions of cis- or trans-β-methylstyrene, suggesting aziridine formation likely to operate via a step-wise pathway. d) Aziridination is not impacted by the presence of potential radical traps. e) PhIO, potentially generated by PhINTs hydrolysis, can give rise to epoxidation products. Epoxides are not on-path to the observed aziridines. f) Proposed reaction mechanism.

A number of observations are relevant to the mechanism by which unactivated olefin aziridination is accomplished by the HFIP-activated iminoiodinanes: First, the reaction of PhINTs with either cis- or trans-β-methylstyrene (1n) in HFIP afforded aziridine 3n as a mixture of 2.0:1.0 cis/trans (from cis-1n) and 1.0:1.7 cis/trans (from trans-1n) (Scheme 4c). The formation of diastereomeric mixtures suggests that aziridination proceeds in a stepwise fashion. The dissimilarity of the diastereomeric ratios from cis- and trans- starting materials indicates that the potential intermediate is too short lived for complete ablation of the starting material stereochemistry. Second, the aziridination of cyclopentene by PhINTs in the presence of a radical trap N-tert-butyl-α-phenylnitrone (PBN) afforded the aziridine product 3b in 60% NMR yield (Scheme 4d), suggesting a radical pathway was unlikely to be operative.

An 1H NMR experiment was carried out to probe the speciation of 2a in HFIP, and we observed that 2a underwent reversible ligand exchange with alcohol solvent to afford ArI(OR)2 and TsNH2 (Supporting Information File 1, Figure S3); similar solvolysis of PhIO in HFIP has been reported [10]. Reaction between cyclohexene and PhIO (2 equiv) in HFIP delivered <10% of cyclohexene oxide; meanwhile, both cyclohexene and cyclohexene oxide were shown to be unreactive towards sulfonamide (Scheme 4e), suggesting that epoxidation is not on path to the observed aziridines. For discussion of side-products and reaction mass balance, see Figure S4 (Supporting Information File 1). Based on these observations, we favor a mechanism in which H-bond activated iminoiodinane reacts directly with the olefin to generate a short-lived alkyl-bound iodinane 7 or iodonium species 8 (Scheme 4f). Ligand coupling from 7 or extrusion of iodobenzene from 8 would furnish a carbocation intermediate 9 which could undergo C–C bond rotation prior to ring closure to form the aziridine product. Such a process would account for the simultaneous stereochemical scrambling observed and the lack of radical trapping noted.

Conclusion

In conclusion, we describe the activation of simple iminoiodinane reagents by fluorinated alcohols, such as HFIP. While most iminoiodinane reagents do not engage aliphatic olefins in the absence of transition metal catalysts, the addition of HFIP enables direct aziridination to be observed. The enhanced reactivity is rationalized as resulting from H-bonding between HFIP and the nitrogen center of the iminoiodinane reagents. 1H NMR data are consistent with such an association and electrochemical data collected in the presence of increasing HFIP concentrations are consistent with H-bonding affording an increasingly strong oxidant. These results demonstrate a simple method for activating iminoiodinane reagents and indicate the potential for chemical non-innocence of fluorinated alcohol solvents in NGT catalysis.

Supporting Information

File 1 Experimental procedures and characterization data, original spectra of new compounds, and optimization details.

Data Availability

All data that supports the findings of this study is available in the published article and/or the supporting information to this article.
==== Refs
1 Wang X Studer A Acc Chem Res 2017 50 1712 1724 10.1021/acs.accounts.7b00148 28636313
2 Yoshimura A Zhdankin V V Chem Rev 2016 116 3328 3435 10.1021/acs.chemrev.5b00547 26861673
3 Akiba K Chemistry of hypervalent compounds 1998 Weinheim, Germany Wiley-VCH
4 Zhdankin V V Hypervalent iodine chemistry: preparation, structure, and synthetic applications of polyvalent iodine compounds 2013 Chichester, UK John Wiley & Sons 10.1002/9781118341155
5 Dauban P Dodd R H Synlett 2003 1571 1586 10.1055/s-2003-41010
6 Hui C Antonchick A P Org Chem Front 2022 9 3897 3907 10.1039/d2qo00739h
7 Ju M Schomaker J M Nat Rev Chem 2021 5 580 594 10.1038/s41570-021-00291-4 37117585
8 Degennaro L Trinchera P Luisi R Chem Rev 2014 114 7881 7929 10.1021/cr400553c 24823261
9 Guo Y Pei C Koenigs R M Nat Commun 2022 13 86 10.1038/s41467-021-27687-6 35013210
10 Cardenal A D Maity A Gao W-Y Ashirov R Hyun S-M Powers D C Inorg Chem 2019 58 10543 10553 10.1021/acs.inorgchem.9b01191 31241320
11 Izquierdo S Essafi S del Rosal I Vidossich P Pleixats R Vallribera A Ujaque G Lledós A Shafir A J Am Chem Soc 2016 138 12747 12750 10.1021/jacs.6b07999 27606591
12 Dasgupta A Thiehoff C Newman P D Wirth T Melen R L Org Biomol Chem 2021 19 4852 4865 10.1039/d1ob00740h 34019066
13 Koller R Stanek K Stolz D Aardoom R Niedermann K Togni A Angew Chem, Int Ed 2009 48 4332 4336 10.1002/anie.200900974
14 Yuan W Szabó K J Angew Chem, Int Ed 2015 54 8533 8537 10.1002/anie.201503373
15 Deng Q-H Wadepohl H Gade L H J Am Chem Soc 2012 134 10769 10772 10.1021/ja3039773 22693950
16 He Y-T Li L-H Yang Y-F Zhou Z-Z Hua H-L Liu X-Y Liang Y-M Org Lett 2014 16 270 273 10.1021/ol403263c 24328396
17 Zhou B Yan T Xue X-S Cheng J-P Org Lett 2016 18 6128 6131 10.1021/acs.orglett.6b03134 27934395
18 Ilchenko N O Tasch B O A Szabó K J Angew Chem 2014 126 47 13111 13115 10.1002/ange.201408812
19 Nagata T Matsubara H Kiyokawa K Minakata S Org Lett 2017 19 4672 4675 10.1021/acs.orglett.7b02313 28829149
20 Zhao Z Racicot L Murphy G K Angew Chem, Int Ed 2017 56 11620 11623 10.1002/anie.201706798
21 Narobe R Murugesan K Schmid S König B ACS Catal 2022 12 1 809 817 10.1021/acscatal.1c05077
22 Matoušek V Pietrasiak E Sigrist L Czarniecki B Togni A Eur J Org Chem 2014 3087 3092 10.1002/ejoc.201402225
23 Shu S Li Y Jiang J Ke Z Liu Y J Org Chem 2019 84 1 458 462 10.1021/acs.joc.8b02741 30499297
24 Thai P Frey B L Figgins M T Thompson R R Carmieli R Powers D C Chem Commun 2023 59 4308 4311 10.1039/d3cc00549f
25 Brantley J N Samant A V Toste F D ACS Cent Sci 2016 2 341 350 10.1021/acscentsci.6b00119 27280169
26 Colomer I Chamberlain A E R Haughey M B Donohoe T J Nat Rev Chem 2017 1 11 0088 10.1038/s41570-017-0088
27 Motiwala H F Armaly A M Cacioppo J G Coombs T C Koehn K R K Norwood V M IV Aubé J Chem Rev 2022 122 15 12544 12747 10.1021/acs.chemrev.1c00749 35848353
28 Koller R Huchet Q Battaglia P Welch J M Togni A Chem Commun 2009 40 5993 5995 10.1039/b913962a
29 Choudhuri K Maiti S Mal P Adv Synth Catal 2019 361 1092 1101 10.1002/adsc.201801510
30 Colomer I Batchelor-McAuley C Odell B Donohoe T J Compton R G J Am Chem Soc 2016 138 8855 8861 10.1021/jacs.6b04057 27380523
31 Yang X-G Zheng K Zhang C Org Lett 2020 22 2026 2031 10.1021/acs.orglett.0c00405 32105085
32 Sarie J C Neufeld J Daniliuc C G Gilmour R ACS Catal 2019 9 7232 7237 10.1021/acscatal.9b02313
33 Minhas H K Riley W Stuart A M Urbonaite M Org Biomol Chem 2018 16 7170 7173 10.1039/c8ob02236d 30246855
34 Tan H Thai P Sengupta U Deavenport I R Kucifer C M Powers D C ChemRxiv 2024 10.26434/chemrxiv-2024-s8gcj
35 Cheng Q-Q Zhou Z Jiang H Siitonen J H Ess D H Zhang X Kürti L Nat Catal 2020 3 386 392 10.1038/s41929-020-0430-4
36 Farndon J J Young T A Bower J F J Am Chem Soc 2018 140 17846 17850 10.1021/jacs.8b10485 30543287
37 Holst D E Wang D J Kim M J Guzei I A Wickens Z K Nature 2021 596 74 79 10.1038/s41586-021-03717-7 34157720
38 Huang Y Zhu S-Y He G Chen G Wang H J Org Chem 2024 89 6263 6273 10.1021/acs.joc.4c00253 38652889
39 Jat J L Chandra D Kumar P Singh V Tiwari B Synthesis 2022 54 4513 4520 10.1055/a-1879-7974
40 Satheesh V Alahakoon I Shrestha K K Iheme L C Marszewski M Young M C Eur J Org Chem 2024 e202301114 10.1002/ejoc.202301114
41 He L Chan P W H Tsui W-M Yu W-Y Che C-M Org Lett 2004 6 2405 2408 10.1021/ol049232j 15228290
42 Li F Zhu W F Empel C Datsenko O Kumar A Xu Y Ehrler J H M Atodiresei I Knapp S Mykhailiuk P K Science 2024 383 6682 498 503 10.1126/science.adm8095 38301027
43 Jurberg I D Nome R A Crespi S Atvars T D Z König B Adv Synth Catal 2022 364 4061 4068 10.1002/adsc.202201095
44 Kuznetsov D M Tumanov V V Smit W A J Polym Res 2013 20 6 128 10.1007/s10965-013-0128-2
45 Noel M Vasu K Cyclic Voltammetry and the Frontiers of Electrochemistry 1990 New Dehli, India Oxford & IBH Publishing
