Hao-Yong Qin,
Houying Gui,
Zai-Wei Zhang,
Tao Shu* and
Hua-Li Qin*
School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China. E-mail: tao.shu@whut.edu.cn; qinhuali@whut.edu.cn
First published on 4th July 2022
A highly efficient regio- and stereoselective Heck–Matsuda method was developed employing aryl diazoniums and allylsulfonyl fluorides for the construction of a class of novel γ-aryl allylsulfonyl fluorides in the presence of Pd(OAc)2 and PPh3. The method features excellent regio- and stereoselectivity (up to 100% E-selectivity), broad substrate scope and mild reaction conditions. Further application of γ-aryl allylsulfonyl fluoride in SuFEx reactions was achieved to provide their corresponding sulfonates and sulfonamides in excellent yields.
Considering the increasing importance of allyl sulfone moiety and sulfonyl fluoride functionality in various fields, the simultaneous introduction of these two moieties into one molecule is highly desirable. However, due to the lack of efficient methods, access to γ-substituted allyl sulfonyl fluoride derivatives still remains less explored. Hence, it is of great significance to design and synthesize various sulfonyl fluoride compounds for the further SuFEx reactions.
The Heck–Matsuda reaction has been recognized as one of the most versatile and powerful synthetic tools for the construction of C–C bond since its discovery by Matsuda.15 Palladium-catalyzed Heck–Matsuda reaction for the synthesis of β-arylethenesulfonyl fluorides from aryl diazonium tetrafluoroborates with exclusive regio- and stereoselectivity has been well studied (Scheme 1a).16 Inspired by this seminal work, we assumed that the Heck–Matsuda reaction would also offer a feasible approach to construct unprecedented γ-aryl allylsulfonyl fluoride molecules. However, controlling regioselectivity and stereoselectiveity of Heck–Matsuda reaction with allylsulfonyl fluoride is still challenging.17 The low selectivity mainly results from the uncontrollable migratory insertion into the olefins (branched vs. linear olefin products) and indiscriminate β-hydride elimination with either Ha or Hb (styrenyl vs. allylic linear olefin products) (Scheme 1b).18 Herein, we report our recent progress of palladium-catalyzed highly regio- and stereoselective Heck–Matsuda reaction for the construction of γ-aryl allylsulfonyl fluorides (3) (Scheme 1c).
Our initial investigation started with the reaction of 4-methylbenzenediazonium tetrafluoroborate (1a, 0.2 mmol) and allylsulfonyl fluoride (2a, 0.4 mmol) in the presence of a catalytic amount of Pd(OAc)2 and PPh3 ligand at 25 °C in DMF (Table 1, entry 1).
Entry | Ligand | 2a (x equiv.) | Solvent | Yield (%) |
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a Reaction conditions: aryldiazonium tetrafluoroborate (1a, 0.2 mmol), Pd(OAc)2 (5 mol%) and PPh3 (5 mol%) were dissolved in solvent (0.2 M, 2.0 mL) before the subsequent addition of allylsulfonyl fluoride (0.4 mmol, 2.0 eq.). Then the resulting mixture was stirred at room temperature for 4 h.b The yields were determined by HPLC using pure 3a as the external standard (tR = 6.1 min, λmax = 258.3 nm, acetonitrile/water = 80![]() ![]() |
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1 | PPh3 | 2.0 | DMF | 66 |
2 | Dppb | 2.0 | DMF | 36 |
3 | Dppf | 2.0 | DMF | Trace |
4 | PPh3 | 2.0 | DMA | 51 |
5 | PPh3 | 2.0 | MeOH | 71 |
6 | PPh3 | 2.0 | Acetone | 16 |
7c | PPh3 | 2.0 | MeOH | 61 |
8d | PPh3 | 2.0 | MeOH | 72 |
9d | PPh3 | 1.1 | MeOH | 78 |
10d | PPh3 | 1.2 | MeOH | 78 |
11d | PPh3 | 1.5 | MeOH | 76 |
To our delight, the 1H NMR of crude product indicated that the (E)-styrenyl product 3a was formed exclusively, while the possible isomeric products were not observed. Subsequently, a variety of ligands such as triphenylphosphine, 1,4-bis(diphenylphosphino) butane (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppf) were screened, and triphenylphosphine was found to be the optimal ligand for this process (Table 1, entry 1–3). The screening of the solvent indicated that methanol was the best choice (Table 1, entry 4–6). Subsequent examination on the loading of catalyst and ligand revealed that 3 mol% Pd(OAc)2 and 3 mol% PPh3 were essential (Table 1, entry 7–8). Reducing the amount of allylsulfonyl fluoride from 2.0 equivalents to 1.1 equivalents led to nearly identical yields of desired product 3a (Table 1, entry 9–11). Therefore, Pd(OAc)2 (3 mol%), PPh3 (3 mol%), allylsulfonyl fluoride (1.1 equiv.) in MeOH (0.1 M) was eventually selected as the optimized conditions for the process.
With the optimized reaction conditions in hand, we next evaluated the substrate scope and functional group tolerance of this protocol using various aryldiazonium tetrafluoroborates (1) and allylsulfonyl fluorides (2). It turned out to be that our protocol was compatible with a broad range of substrates, delivering the desired products with excellent selectivity in most cases. Besides, the substrates bearing whether electron-donating groups (1a, 1c, 1k, 1n, 1o, and 1r) or electron-withdrawing groups (1d–1j, 1l, 1m, 1q, and 1v) all worked well. In addition, ortho-, meta-, or para-mono-substituted and multi-substituted diazonium (1r–1v) salts all afforded their corresponding products in moderate to good yields. It is worth noting that the halogen atom on the aromatic rings of aryldiazonium tetrafluoroborates (1d–1f, 1l, 1m, 1p, and 1v) tolerated well and delivered their corresponding products in acceptable yields, while the C (sp2)–X bond remained untouched during the transformations. Nitro-substituted (1g) diazonium salt was also successfully converted into the corresponding allyl sulfonyl fluoride with moderate yield (3g, 56% yield) (Table 2). Furthermore, the allylsulfonyl fluoride with a methyl substituent on the vinyl skeleton (2b) was also compatible with the reaction system, albeit a moderate yield of the product (3w) was achieved. And the E configuration of compound 3w was confirmed by NOE analysis (see the ESI† for details).
a Reaction conditions: aryldiazonium tetrafluoroborate (1, 1.0 mmol), Pd(OAc)2 (3 mol%) and PPh3 (3 mol%) were dissolved in MeOH (0.1 M), before the subsequent addition of allylsulfonyl fluoride (1.1 mmol, 1.1 eq.). The resulting mixture was stirred at room temperature under air. The selectivity for (E)-styrene was >20![]() ![]() ![]() ![]() ![]() ![]() |
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To demonstrate the practicality of this method, a series of gram-scale reactions were performed under the optimal reaction conditions (Scheme 2). And the research results revealed that these reactions worked well to transform the corresponding aryldiazonium tetrafluoroborates (1b, 1d, 1k, 1q, and 1t) into their corresponding products (3b, 3d, 3k, 3q, and 3t) in moderate to excellent yields (50–96%).
Some extended work focusing on the chemical transformations of this class of novel sulfonyl fluoride molecules was carried out as described in the Scheme 3. (E)-3-Phenylprop-2-ene-1-sulfonyl fluoride (3b) was successfully converted into sulfonamide (4) in nearly quantitative yield (99%) when coupled with morpholine in the presence of Et3N. Furthermore, the SuFEx reactions of (E)-3-phenylprop-2-ene-1-sulfonyl fluoride (3b) with phenol or alcohols also proceeded smoothly, delivering the sulfonates (5, 6a, and 6b) in good to excellent yields (67–97%).
Footnote |
† Electronic supplementary information (ESI) available. See https://doi.org/10.1039/d2ra03733e |
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