Abstract
In recent years, numerous 1,2-R shift (R = aliphatic or aryl) based on tetracoordinate boron species have been well investigated. In the contrary, the corresponding radical migrations, especially 1,2-boryl radical shift for the construction of organoborons is still in its infancy. Given the paucity and significance of such strategies in boron chemistry, it is urgent to develop other efficient and alternative synthetic protocols to enrich these underdeveloped radical 1,2-boron migrations, before their fundamental potential applications could be fully explored at will. Herein, we have demonstrated a visible-light-induced photoredox neutral decarboxylative radical cross-coupling reaction, which undergoes a radical 1,2-boron shift to give a translocated C-radical for further capture of versatile radical acceptors. The mild reaction conditions, good functional-group tolerance, and broad β-boryl NHPI esters scope as well as versatile radical acceptors make this protocol applicable in modification of bioactive molecules. It can be expected that this methodology will be a very useful tool and an alternative strategy for the construction of primary organoborons via a novel radical 1,2-boron shift mode.
Similar content being viewed by others
Introduction
Boron-containing compounds are important linchpins in organic synthesis1,2,3,4,5,6 and also play an important role in material science and pharmaceuticals7. As the key intermediates, organoborons have been extensively employed in various cross-coupling reactions8,9,10,11,12. Among them, 1,2-metallate migration reactions and transmetallations of tetracoordinate boron species are the most prevalent and well-recognized reaction modes11,13,14,15,16,17,18. In fact, stereospecific 1,2-migrations of alkenylboronate complexes have been known for many decades. In 1967, Zweifel and co-workers reported the first 1,2-alkyl/aryl migrations of vinylboron “ate” complexes (e.g. alkenyl tetracoordinate boron species) induced by electrophilic halogenation19. In 2016, Morken and co-workers disclosed an enantioselective palladium-induced 1,2-alkyl/aryl migration of the same substrates20,21,22,23,24. More recently, Studer25,26,27,28,29,30,31, Aggarwal32,33,34,35,36,37,38,39,40, and Renaud41 developed radical–polar crossover reactions, in which 1,2-alkyl/aryl migrations of alkenyl tetracoordinate boron species are induced by alkyl radical additions (Fig. 1A). In recent years, radical borylations under transition-metal-free conditions, especially alkyl radical-involved borylations dramatically promote the expansion of organoborons. Although numerous 1,2-R shift (R = aliphatic or aryl) based on tetracoordinate boron species have been well investigated, the corresponding radical migrations, especially 1,2-boryl radical shifts are underdeveloped and elusive. There are only very few cases describing such migrations42. For instance, in 1999, Batey and Smil disclosed that boron-tethered radical cyclizations could undergo a 1,2-boryl radical shift (Fig. 1B, eq. a)43, however, no significant progress has been achieved until 2019, in that year Aggarwal and coworkers reported a photoredox catalysis-promoted activation of 1,2-bis-boronic esters to lead to primary β-boryl radicals, which further undergo rapid 1,2-boron shift to form thermodynamically favored secondary radicals, finally affording significant functionalized boronic esters (Fig. 1B, eq. b)44,45,46. Later on, alkynyl triflones as CF3-radical precursors as well as the subsequent alkynylation reagents are employed for the trifunctionalization of allylic boronates, which represents a new 1,2-boryl radical migration strategy was disclosed by Studer and co-workers (Fig. 1B, eq. c)47,48. Despite these achievements, efficient 1,2-boryl radical migration for the construction of organoborons is still in its infancy. Given the paucity and significance of such strategies in boron chemistry, it is urgent to develop other efficient and alternative synthetic protocols to enrich these underexplored radical 1,2-boron migrations from readily accessible starting materials, before their fundamental potential applications can be fully explored at will.
N-Hydroxyphthalimide (NHPI) esters, which could be readily accessible from the corresponding carboxylic acids, have emerged as efficient alkyl radical precursors to be coupled with radical acceptors, nucleophiles (such as amines, alcohols, borons, etc) or electrophiles49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64. Therefore, we decided to use boron-containing NHPI esters named β-boryl NHPI esters as radical precursors, presumably, decarboxylation of such boron compounds under the action of light would produce β-boryl alkyl radicals, which could be used for further investigations of the elusive radical 1,2-boron migration reactions.
According to retrosynthetic analysis, β-boryl NHPI esters could be readily accessible from β-boryl esters, which are the result of Cu-catalyzed β-boration of various α,β-unsaturated carbonyl compounds65. After extensive efforts, we found that β-boryl NHPI ester 1a could be practically obtained on a 10-gram scale with a 66% overall yield. The structure of 1a is confirmed by X-ray crystal structure analysis (Fig. 1C, left). Furthermore, we were intrigued as to whether our approach could be extended to the selective functionalization of β-gem-diboryl NHPI esters. In this proposed strategy, a radical 1,2-boron migration would enable a thermodynamically favored boron-bearing tertiary alkyl radical, thus resulting in 1,2-diboron compounds. Remarkably, the β-boryl NHPI esters and β-gem-diboryl NHPI esters are white solids and are stable in air for months. Thus, the advantages of such compounds make them practical and accessible to synthetic and medicinal researchers. In the presence of photo-catalysis, these β-boryl NHPI esters could undergo facile single-electron transfer followed by rapid decarboxylative fragmentation to lead to a β-boryl alkyl radical, which then might engage in a radical 1,2-boron shift. The migration will be steered by thermodynamic effects with the increased stability of the rearranged C-radical. Trapping of the translocated rearranged radical via cross-coupling reactions could render versatile mono primary boronic esters with β-boryl NHPI esters (Fig. 1D). Of note, besides various secondary β-boryl NHPI esters, β-gem-diboryl NHPI esters are well tolerated under this transformation as well, thus rendering various aliphatic 1,2-diborons. The mild reaction conditions, good functional-group tolerance, and broad β-boryl and β-gem-diboryl NHPI esters scope as well as versatile radical acceptors make this protocol applicable in the modification of bioactive molecules.
Results
To validate our hypothesis, we initiated an optimization study of a model reaction between 1,3-dioxoisoindolin-2-yl 4,4-dimethyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pentanoate (1a) and ((phenylethynyl)sulfonyl)benzene (2a) in the presence of a photocatalyst and a base under a blue LED lamp (Table 1). The desired cross-coupling product 3a was obtained in 52% isolated yield when using Ir(ppy)3 as a photocatalyst, diisopropylethylamine (DIPEA)/Hantzsch ester (HE) as the reductants, DCM as a solvent, and under the irradiation of a 40 W blue LED lamp (entry 1, Table 1). A screening of photocatalysts, such as [Ir(dtbppy)(ppy)2]PF6, [Ir{dFCF3ppy}2(bpy)]PF6, 4CzIPN, and so on, demonstrated that Ir(ppy)3 was the most effective catalyst, yielding 3a in 52% yield (entries 2–7, Table 1. Also see Supplementary Information (SI) for details). Solvent examinations showed that DCE was the optimal one to deliver the target product 3a in 74% yield (entries 8–11, Table 1). Further assessment on the amount of reductants indicated that 1.5 equiv. HE and 2 equiv. DIPEA were the best combination (entries 12–15, Table 1). Finally, control experiments demonstrated that the visible light, photocatalyst and HE were all necessary for this transformation, as no desired product 3a was obtained in the absence of any of the above reaction promoters (entries 16–19, Table 1).
Substrate scopes
With the optimum conditions in hand (entry 10, Table 1), the scope of this decarboxylative alkynylation of β-boryl NHPI esters was explored and the results were shown in Fig. 2. This protocol was applicable to a wide range of alkynyl arylsulfones with either electron‐donating or electron‐withdrawing substituents on the benzene rings, affording the corresponding products 3a–3g in moderate to good yields (61–76%). Next, various secondary β-boryl NHPI esters were prepared and subjected to the standard conditions, to our delight, they could react smoothly with alkynyl arylsulfone 2 and delivered the target products 3h–3s in decent yields. For instance, in terms of β-boryl NHPI esters bearing a secondary carbon on α-position, both cyclic (including five-membered and six-membered cyclic rings) and acyclic alkyl groups were compatible and converted into corresponding alkynylation products in moderate yields (3h–3k). For β-boryl NHPI esters bearing a primary carbon on α-position, phenylethyl (1l) and isopropyl ethyl (1o) were also suitable candidates for this transformation and the corresponding products 3l and 3o were obtained in 66% and 68% yields, respectively. To understand the impact of the stability of radicals on the reactivity and selectivity, substrates (1m, 1n) containing methylene tethers with different lengths were exposed to the reaction as well, it was found that the length of the chain does not affect the formation of the desired products. Moreover, for the tertiary alkyl group in β-boryl NHPI esters (1p), the corresponding target product 3p could also be obtained successfully albeit in a lower yield. To showcase the applicability and practicality of this method, we also employed the late-stage modifications of some bioactive compounds or drug molecules. For example, a series of natural products (dodecyl aldehyde, Cyclamen aldehyde, Lily aldehyde) were also successfully introduced into the β-boryl NHPI esters, and they all reacted well with alkynyl arylsulfones and produced the corresponding products (3q, 3r and 3s) without loss of efficiency. Moreover, we have examined β-boryl NHPI esters (using B2neop2 as the boron source for 1,2-boron shift). The substrate was also compatible with our reaction system to deliver the desired product 3t in decent yield. After establishing the approach for the construction of Csp3–Csp bonds, we were especially interested in forging Csp3–Csp2 bonds by using vinyl sulfones as coupling partners. As expected, these substrates were equipotent to afford the corresponding coupling products (3u–3z) with Csp2–Csp3 bond formation in moderate yields under the standard conditions just like with alkynyl arylsulfones as substrates.
Encouraged by the aforementioned results, we subsequently evaluated the scope of allyl sulfones (Fig. 3). It turned out that allyl sulfones were suitable radical acceptors as well, and these substrates demonstrated good reactivities, and the corresponding coupling products were rendered in moderate to excellent yields (5a–5ab) under reoptimized conditions as follows: using fluorescein as photocatalyst, HE and DIPEA as the reductants, DCE as solvent, and under the irradiation of a 40 W blue LED lamp base at rt for 12 h under argon atmosphere (see SI for details). The results were summarized in Fig. 3. We found that a broad range of allyl sulfones were compatible substrates for this decarboxylative allylation of β-boryl NHPI esters, and the corresponding desired products were procured with yields ranging from 50% to 83% (5a–5p). Both electron-donating and electron-withdrawing substituents on the para and meta positions of the benzene rings (5b–5h) worked well in our catalytic system to afford the corresponding allylation products in moderate to excellent yields. This catalytic system was also amenable to naphthalene and heterocycles, and the corresponding products 5i–5j were isolated in good yields. In addition to aryl-substituted substrates, other allyl sulfones, such as halogenated and ester-substituted allyl sulfones, have also been confirmed to participate in the reactions well to obtain the corresponding homoallylic boronates (5k–5p). Allyl sulfones derived from structurally complicated natural products such as nerol, dl-menthol and citronellol, all reacted well and produced the corresponding products in synthetically useful yields (5n–5p). It is indicated that various substituted β-boryl NHPI esters and ethyl 2-((phenylsulfonyl)methyl)acrylate were also well-suited for this transformation (5q–5ab). For boron sources containing other substituents (using B2neop2 as the boron source for 1,2-boron shift), it was also compatible with this reaction system to render the target product 5ac in good yield.
To further extend the scope of the present method, our interest subsequently shifted to investigation of other radical acceptors (Fig. 4). Radical conjugate addition to a range of electron-deficient alkenes afforded the desired products (7a–7m) in good to excellent yields. In addition to ethyl acrylates, a series of alkyls, such as tert-butyl, benzyl, phenyl acrylates and other substituent groups were viable substrates to give the corresponding products (7a–7d, 7k–7m) as well. Furthermore, this photoredox system could enable decarboxylative alkylation of the β-boryl NHPI esters with other electron-deficient alkenes such as acrylonitrile, vinyl phosphonates, vinyl amides, vinyl sulfones with good efficiency (7e–7j). For β-boryl NHPI esters, various substrates could furnish the desired products (7n–7x) smoothly.
Interestingly, with our current strategy, when β-gem-diboryl NHPI esters were employed as the substrates, the reaction worked perfectly to lead to the corresponding new 1,2-diboron products. As summarized in Fig. 5, allyl sulfones regardless of aromatic ring or chlorine atom substituents all proved to be suitable substrates, leading to the desired products in good yields (8a–8l). Of note, alkynyl phenylsulfones were well tolerated to afford the desired products in moderate yields (8m–8o).
Downstream applications and transformations
To demonstrate the synthetic utility of this coupling protocol, several scale-ups and transformations were performed, shown in Fig. 6. First of all, the scalabilities were performed by gram-scale reactions on 3a, 5a, and 7a, without significant erosion of efficiency (Fig. 6A). In order to showcase practical values of this strategy, then a series of transformations on 3a were conducted. For example, firstly, the boron moiety could be oxidized into hydroxyl groups to lead to 9 in 85% yield (Fig. 6B, eq. a). Then, the boron moiety could also be retained through conversion to the corresponding potassium trifluoroborate salt 10, which can be conveniently isolated (Fig. 6B, eq. b). Next, carbon homologations were achieved through the incorporation of an alkene group 11 at the C-B terminus with Grignard reagents (Fig. 6B, eq. c). The 3a was smoothly converted to aryl groups via Suzuki–Miyaura couplings under the identified conditions, rendering the product 12 in 68% yield and the product 13 in 53% yield (Fig. 6B, eq. d). The introduction of (hetero)aryl motifs was within reach by treatment with organolithium reagents (14 and 15, Fig. 6B, eq. e and eq. f). And the alkyne 4a could undergo complete hydrogenation with Pd/C catalyst, providing 16 in 90% yield (Fig. 6B, eq. g), which features a saturated aliphatic chain.
Mechanism investigations
To gain more insights into this transformation, we carried out some control experiments and mechanistic studies. The reaction was completely suppressed in the presence of radical scavengers such as TEMPO, BHT, or 1,1-diphenylethylene, and the radical trapping products 17–19 could be detected by HRMS (Fig. 7a). The above results revealed that this process might proceed via a radical pathway. We subsequently turned our attention to the radical-clock experiments. Compound 20 undertook decarboxylation to produce a radical, which participated in our transformation through the way of intramolecular cyclization, thus confirming the radical process (Fig. 7b).
Based on the above control experiments, a possible reaction mechanism is proposed as outlined in Fig. 8. Photocatalyst Ir(ppy)3 is excited to photoexcited Ir(III)* via single-electron transfer under visible light, the latter is then reduced by Hantzsch ester to Ir(II). Single-electron transfer from visible light-excited photocatalyst Ir(III) to the N-hydroxyphthalimide 1 generates a radical anion A, which then undergoes homolytic cleavage of the N–O bond to deliver alkyl radical B by decarboxylation and the release of phthalimide anion. The alkyl radical B thus engages in a 1,2-boron shift to form C. After α-addition to the alkynyl sulfone 2 and the sulfonyl radical elimination, the alkyne product 3 is obtained. With the proton transfer from the Hantzsch ester radical cation, β-boryl alkyl radical then adds either to the allyl sulfone 4 to obtain the allylation adduct 5 after desulfonation or to the Michael acceptor to obtain the Michael addition adduct 7.
Discussion
In conclusion, we have demonstrated a visible-light-induced photoredox neutral radical decarboxylative cross-coupling reaction, which undergoes a radical 1,2-boron shift to give a translocated C-radical for further capture of versatile radical acceptors. The method features mild conditions and simple operations, avoids the use of highly active organometallic reagents, and enriches the diversity of substrates. Given the ready accessibility of the starting materials, the operational simplicity, and the valuable products, it can be expected that this methodology will be a very useful tool and an alternative strategy for the construction of organoborons via a novel radical 1,2-boron shift mode. Furthermore, β-gem-diboryl NHPI esters undergo a 1,2-boron shift to give 1,2-dibrons or 1,2-diols after oxidation.
Methods
General procedure for synthesis of primary boronates from alkynyl arylsulfones or vinyl sulfones
A mixture of 1 (0.2 mmol), 2 (0.3 mmol), Ir(ppy)3 (1% mmol), and HE (0.3 mmol) were charged into a Schleck tube, then the air was removed, argon was filled of Schleck tube and DIPEA (0.2 mmol), DCE (2 mL) is added the mixture. The mixture was stirred under irradiation from 40 W Blue LEDs. After the solvent was removed under reduced pressure, the residue was purified by silica gel chromatography using PE/EA (50:1) to afford the corresponding product.
General procedure for synthesis of primary boronates from allyl sulfones
A mixture of 1 (0.2 mmol), fluorescein (1% mmol), and HE (0.4 mmol) was charged into a Schleck tube, then the air was removed, argon was filled in a Schleck tube and 4 (0.3 mmol), DIPEA (0.2 mmol), HCOOH (0.2 mmol), DCM (2 mL) is added the mixture. The mixture was stirred under irradiation from 40 W Blue LEDs. After the solvent was removed under reduced pressure, the residue was purified by silica gel chromatography using PE/EA (50:1) to afford the corresponding product.
General procedure for synthesis of primary boronates from electron-deficient alkenes
A mixture of 1 (0.2 mmol), Ru(bpy)3Cl2 (1% mmol), and HE (0.3 mmol) was charged into a Schleck tube, then the air was removed, argon was filled in a Schleck tube and 6 (0.3 mmol), THF (2 mL) is added the mixture. The mixture was stirred under irradiation from 40 W Blue LEDs. After the solvent was removed under reduced pressure, the residue was purified by silica gel chromatography using PE/EA (30:1) to afford the corresponding product.
Data availability
The data that support the findings of this study are available within the article and its Supplementary Information files. All other data are available from the corresponding author upon request. The X-ray crystallographic coordinates for structures 1a and 3e reported in this article have been deposited at the Cambridge Crystallographic Data Centre (CCDC), under deposition numbers CCDC 2247689 (1a) and 2242317 (3e). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
References
Miyaura, N. & Suzuki, A. Palladium-catalyzed cross-coupling reactions of organoboron compounds. Chem. Rev. 95, 2457–2483 (1995).
Suzuki, A. Cross-coupling reactions of organoboranes: an easy way to construct C–C bonds (Nobel lecture). Angew. Chem. Int. Ed. 50, 6722–6737 (2011).
Leonori, D. & Aggarwal, V. K. Stereospecific couplings of secondary and tertiary boronic esters. Angew. Chem. Int. Ed. 54, 1082–1096 (2015).
Fyfe, J. W. B. & Watson, A. J. B. Recent developments in organoboron chemistry: old dogs, new tricks. Chem 3, 31–55 (2017).
Sandford, C. & Aggarwal, V. K. Stereospecific functionalizations and transformations of secondary and tertiary boronic esters. Chem. Commun. 53, 5481–5494 (2017).
Jin, S., Liu, K., Wang, S. & Song, Q. Enantioselective cobalt-catalyzed cascade hydrosilylation and hydroboration of alkynes to access enantioenriched 1,1-silylboryl alkanes. J. Am. Chem. Soc. 143, 13124–13134 (2021).
Brooks, W. L. A. & Sumerlin, B. S. Synthesis and applications of boronic acid-containing polymers: from materials to medicine. Chem. Rev. 116, 1375–1397 (2016).
Ollivier, C. & Renaud, P. Organoboranes as a source of radicals. Chem. Rev. 101, 3415–3434 (2001).
Duret, G., Quinlan, R., Bisseret, P. & Blanchard, N. Boron chemistry in a new light. Chem. Sci. 6, 5366–5382 (2015).
Wang, L. et al. C–O Functionalization of α-oxyboronates: a deoxygenative gem-diborylation and gem-silylborylation of aldehydes and ketones. J. Am. Chem. Soc. 139, 5257–5264 (2017).
Zhao, B. et al. An olefinic 1,2-boryl-migration enabled by radical addition: construction of gem-Bis(boryl)alkanes. Angew. Chem. Int. Ed. 58, 9448–9452 (2019).
Yang, K. & Song, Q. Tetracoordinate boron intermediates enable unconventional transformations. Acc. Chem. Res. 54, 2298–2312 (2021).
Leonori, D. & Aggarwal, V. K. Lithiation-borylation methodology and its application in synthesis. Acc. Chem. Res. 47, 3174–3183 (2014).
Yang, K., Zhang, F., Fang, T., Zhang, G. & Song, Q. Stereospecific 1,4-metallate shift enables stereoconvergent synthesis of ketoximes. Angew. Chem. Int. Ed. 58, 13421–13426 (2019).
Wang, H., Jing, C., Noble, A. & Aggarwal, V. K. Stereospecific 1,2-migrations of boronate complexes induced by electrophiles. Angew. Chem. Int. Ed. 59, 16859–16872 (2020).
Yang, K. et al. Transition-metal-free double-insertive coupling of isocyanides with arylboronic acids enabled diarylmethanamines. Cell Rep. Phys. Sci. 1, 100268 (2020).
Li, C. et al. Photo-induced trifunctionalization of bromostyrenes via remote radical migration reactions of tetracoordinate boron species. Nat. Commun. 13, 1784 (2022).
Zhang, F. et al. An olefinic 1,2-α-boryl migration enables 1,2-bis(boronic esters) via radical-polar crossover reaction. Chin. J. Chem. 40, 582–588 (2022).
Zweifel, G., Arzoumanian, H. & Whitney, C. C. A convenient stereoselective synthesis of substituted alkenes via hydroboration-iodination of alkynes. J. Am. Chem. Soc. 89, 3652–3653 (1967).
Zhang, L. et al. Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement. Science 351, 70–74 (2016).
Chierchia, M., Law, C. & Morken, J. P. Nickel-catalyzed enantioselective conjunctive cross-coupling of 9-BBN borates. Angew. Chem. Int. Ed. 56, 11870–11874 (2017).
Edelstein, E. K., Namirembe, S. & Morken, J. P. Enantioselective conjunctive cross-coupling of bis(alkenyl)borates: a general synthesis of chiral allylboron reagents. J. Am. Chem. Soc. 139, 5027–5030 (2017).
Lovinger, G. J., Aparece, M. D. & Morken, J. P. Pd-catalyzed conjunctive cross-coupling between Grignard-derived boron “ate” complexes and C(sp2) halides or triflates: NaOTf as a Grignard activator and Halide scavenger. J. Am. Chem. Soc. 139, 3153–3160 (2017).
Myhill, J. A., Zhang, L., Lovinger, G. J. & Morken, J. P. Enantioselective construction of tertiary boronic esters by conjunctive cross-coupling. Angew. Chem. Int. Ed. 57, 12799–12803 (2018).
Kischkewitz, M., Okamoto, K., Mück-Lichtenfeld, C. & Studer, A. Radical-polar crossover reactions of vinylboron ate complexes. Science 355, 936–938 (2017).
Gerleve, C., Kischkewitz, M. & Studer, A. Synthesis of α-chiral ketones and chiral alkanes using radical polar crossover reactions of vinyl boron ate complexes. Angew. Chem. Int. Ed. 57, 2441–2444 (2018).
Kischkewitz, M., Gerleve, C. & Studer, A. Radical-polar crossover reactions of dienylboronate complexes: synthesis of functionalized allylboronic esters. Org. Lett. 20, 3666–3669 (2018).
You, C. & Studer, A. Synthesis of 1,3-bis-(boryl)alkanes through boronic ester induced consecutive double 1,2-migration. Angew. Chem. Int. Ed. 59, 17245–17249 (2020).
Wang, D., Mück-Lichtenfeld, C., Daniliuc, C. G. & Studer, A. Radical aryl migration from boron to carbon. J. Am. Chem. Soc. 143, 9320–9326 (2021).
You, C. et al. Regio- and stereoselective 1,2-carboboration of ynamides with aryldichloroboranes. Angew. Chem. Int. Ed. 60, 21697–21701 (2021).
You, C. & Studer, A. Three-component 1,2-carboamination of vinyl boronic esters via amidyl radical induced 1,2-migration. Chem. Sci. 12, 15765–15769 (2021).
Ganesh, V., Odachowski, M. & Aggarwal, V. K. Alkynyl moiety for triggering 1,2-metallate shifts: enantiospecific sp2–sp3 coupling of boronic esters with p-arylacetylenes. Angew. Chem. Int. Ed. 56, 9752–9756 (2017).
Silvi, M., Sandford, C. & Aggarwal, V. K. Merging photoredox with 1,2-metallate rearrangements: the photochemical alkylation of vinyl boronate complexes. J. Am. Chem. Soc. 139, 5736–5739 (2017).
Fawcett, A., Biberger, T. & Aggarwal, V. K. Carbopalladation of C–C σ-bonds enabled by strained boronate complexes. Nat. Chem. 11, 117–122 (2019).
Fawcett, A., Murtaza, A., Gregson, C. H. U. & Aggarwal, V. K. Strain-release-driven homologation of boronic esters: application to the modular synthesis of azetidines. J. Am. Chem. Soc. 141, 4573–4578 (2019).
Bennett, S. H. et al. Difunctionalization of C–C σ-bonds enabled by the reaction of bicyclo[1.1.0]butyl boronate complexes with electrophiles: reaction development, scope, and stereochemical origins. J. Am. Chem. Soc. 142, 16766–16775 (2020).
Davenport, R. et al. Visible-light-driven strain-increase ring contraction allows the synthesis of cyclobutyl boronic esters. Angew. Chem. Int. Ed. 59, 6525–6528 (2020).
Hari, D. P., Abell, J. C., Fasano, V. & Aggarwal, V. K. Ring-expansion induced 1,2-metalate rearrangements: highly diastereoselective synthesis of cyclobutyl boronic esters. J. Am. Chem. Soc. 142, 5515–5520 (2020).
Yu, S., Jing, C., Noble, A. & Aggarwal, V. K. 1,3-Difunctionalizations of [1.1.1]propellane via 1,2-metallate rearrangements of boronate complexes. Angew. Chem. Int. Ed. 59, 3917–3921 (2020).
Hari, D. P., Madhavachary, R., Fasano, V., Haire, J. & Aggarwal, V. K. Highly diastereoselective strain-increase allylborations: rapid access to alkylidenecyclopropanes and alkylidenecyclobutanes. J. Am. Chem. Soc. 143, 7462–7470 (2021).
Fasano, V., Cid, J., Procter, R. J., Ross, E. & Ingleson, M. J. Selective boryl-anion migration in a vinyl sp2–sp3 diborane induced by soft borane Lewis acids. Angew. Chem. Int. Ed. 57, 13293–13297 (2018).
Jiang, X.-M. et al. 1,2-Boryl migration enables efficient access to versatile functionalized boronates. Eur. J. Org. Chem. 2022 e202101463 (2022).
Batey, R. A. & Smil, D. V. The first boron-tethered radical cyclizations and intramolecular homolytic substitutions at boron. Angew. Chem. Int. Ed. 38, 1798–1800 (1999).
Kaiser, D., Noble, A., Fasano, V. & Aggarwal, V. K. 1,2-Boron shifts of β-boryl radicals generated from bis-boronic esters using photoredox catalysis. J. Am. Chem. Soc. 141, 14104–14109 (2019).
Wang, H., Han, W., Noble, A. & Aggarwal, V. K. Dual nickel/photoredox-catalyzed site-selective cross-coupling of 1,2-bis-boronic esters enabled by 1,2-boron shifts. Angew. Chem. Int. Ed. 61, e202207988 (2022).
Wang, H., Wu, J., Noble, A. & Aggarwal, V. K. Selective coupling of 1,2-bis-boronic esters at the more substituted site through visible-light activation of electron donor–acceptor complexes. Angew. Chem. Int. Ed. 61, e202202061 (2022).
Jana, K., Bhunia, A. & Studer, A. Radical 1,3-difunctionalization of allylboronic esters with concomitant 1,2-boron shift. Chem 6, 512–522 (2020).
Jana, K. & Studer, A. Allylboronic esters as acceptors in radical addition, boron 1,2-migration, and trapping cascades. Org. Lett. 24, 1100–1104 (2022).
Xue, W. & Oestreich, M. Copper-catalyzed decarboxylative radical silylation of redox-active aliphatic carboxylic acid derivatives. Angew. Chem. Int. Ed. 56, 11649–11652 (2017).
Zhao, W., Wurz, R. P., Peters, J. C. & Fu, G. C. Photoinduced, copper-catalyzed decarboxylative C–N coupling to generate protected amines: an alternative to the Curtius rearrangement. J. Am. Chem. Soc. 139, 12153–12156 (2017).
Minozzi, C., Caron, A., Grenier-Petel, J.-C., Santandrea, J. & Collins, S. K. Heteroleptic copper(I)-based complexes for photocatalysis: combinatorial assembly, discovery, and optimization. Angew. Chem. Int. Ed. 57, 5477–5481 (2018).
Wang, C. et al. Visible-light-driven, copper-catalyzed decarboxylative C(sp3)–H alkylation of glycine and peptides. Angew. Chem. Int. Ed. 57, 15841–15846 (2018).
Crespi, S. & Fagnoni, M. Generation of alkyl radicals: from the tyranny of tin to the photon democracy. Chem. Rev. 120, 9790–9833 (2020).
Xia, H.-D. et al. Photoinduced copper-catalyzed asymmetric decarboxylative alkynylation with terminal alkynes. Angew. Chem. Int. Ed. 59, 16926–16932 (2020).
Cheung, K. P. S., Sarkar, S. & Gevorgyan, V. Visible Light-Induced Transition Metal Catalysis. Chem. Rev. 122, 1543–1625 (2022).
Wang, D., Zhu, N., Chen, P., Lin, Z. & Liu, G. Enantioselective decarboxylative cyanation employing cooperative photoredox catalysis and copper catalysis. J. Am. Chem. Soc. 139, 15632–15635 (2017).
Dong, X.-Y. et al. A general asymmetric copper-catalysed Sonogashira C(sp3)–C(sp) coupling. Nat. Chem. 11, 1158–1166 (2019).
Chandrachud, P. P., Wojtas, L. & Lopchuk, J. M. Decarboxylative amination: diazirines as single and double electrophilic nitrogen transfer reagents. J. Am. Chem. Soc. 142, 21743–21750 (2020).
Huang, H.-M. et al. Catalytic radical generation of π-allylpalladium complexes. Nat. Chem. 3, 393–400 (2020).
Guo, Y., Luo, Y., Mu, S., Xu, J. & Song, Q. Photoinduced decarboxylative phosphorothiolation of N-hydroxyphthalimide esters. Org. Lett. 23, 6729–6734 (2021).
Li, R.-H. et al. Photocatalytic C(sp3)–O/N cross-couplings by NaI-PPh3/CuBr cooperative catalysis: computational design and experimental verification. ACS Catal. 11, 6633–6642 (2021).
Planas, F., Costantini, M., Montesinos-Magraner, M., Himo, F. & Mendoza, A. Combined experimental and computational study of ruthenium N-hydroxyphthalimidoyl carbenes in alkene cyclopropanation reactions. ACS Catal. 11, 10950–10963 (2021).
Guo, Y. et al. Design, synthesis, and applications of ortho-sulfur substituted arylphosphanes. CCS Chem. 5, 1353–1364 (2022).
Ai, H., Ma, X., Song, Q. & Wu, X. C–F bond activation under transition-metal-free conditions. Sci. China Chem. 64, 1630–1659 (2021).
Mun, S., Lee, J.-E. & Yun, J. Copper-catalyzed β-boration of α,β-unsaturated carbonyl compounds: rate acceleration by alcohol additives. Org. Lett. 8, 4887–4889 (2006).
Acknowledgements
Financial support from National Natural Science Foundation of China (21602065 to J.X., 21931013 and 22271105 to Q.S.), the Natural Science Foundation of Fujian Province (2022J02009 to Q.S.), Promotion Program for Young and Middle-aged Teacher in Science and Technology Research of Huaqiao University (ZQN-705 to J.X.) and Open Research Fund of School of Chemistry and Chemical Engineering, Henan Normal University (to Q.S.) is gratefully acknowledged. We also thank the Instrumental Analysis Center of Huaqiao University for its analysis support.
Author information
Authors and Affiliations
Contributions
Q.S. and J.X. conceived and directed the project. Y.G., X.W., C.L., and J.S. performed experiments. J.X. and Y.G. prepared the Supplementary Information. Q.S. and Y.G. prepared the manuscript. All authors discussed the results and commented on the manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Guo, Y., Wang, X., Li, C. et al. Decarboxylation of β-boryl NHPI esters enables radical 1,2-boron shift for the assembly of versatile organoborons. Nat Commun 14, 5693 (2023). https://doi.org/10.1038/s41467-023-41254-1
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41467-023-41254-1
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.