# Chemo- and Regioselective Palladium-Catalyzed Internal Hydrosilylation of gem-Difluoroallenes to Access *β*-Fluorinated Vinylsilanes

Xin-Long Yu, An-Jiu Wen, Zheng Xu, Samuel Couve-Bonnaire, Li-Wen Xu, Jean-Philippe Bouillon

► To cite this version:

Xin-Long Yu, An-Jiu Wen, Zheng Xu, Samuel Couve-Bonnaire, Li-Wen Xu, et al.. Chemo- and Regios- elective Palladium-Catalyzed Internal Hydrosilylation of gem-Difluoroallenes to Access *β*-Fluorinated Vinylsilanes. ACS Catalysis, 2025, 15 (16), pp.13747-13756. 10.1021/acscatal.5c03553 . hal- 05505541

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Distributed under a Creative Commons CC BY 4.0 - Attribution - International License
Chemo- and Regio-selective Palladium-Catalyzed Internal
Hydrosilylation of gem-Difluoroallenes to Access β-
Fluorinated Vinylsilanes

Xin-Long Yu,[a] An-Jiu Wen,[b] Zheng Xu,[b] Samuel Couve-Bonnaire*,[a] Li-Wen Xu*,[b] Jean-Philippe Bouillon*[a]

[a] Univ Rouen Normandie, INSA Rouen Normandie, Univ Caen Normandie, ENSICAEN, CNRS, Institut CARMEN UMR 6064, F-76000 Rouen, France

[b] Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, and Zhejiang Key Laboratory of Organosilicon Material Technology, College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, P. R. China.

KEYWORDS: gem-difluoroallene; vinylsilane; palladium; catalysis; hydrosilylation

**ABSTRACT:** Hydrosilylation represents one of the most important transformations in organosilicon chemistry and homogeneous catalysis. While terminal alkene hydrosilylation has been extensively studied, catalytic hydrosilylation of internal alkenes remains significantly underdeveloped. In this work, we report a highly efficient palladium-catalyzed internal hydrosilylation of *gem*-difluoroallenes, providing straightforward access to valuable *gem*-difluorovinylsilanes. The reaction proceeds with excellent regio- and chemoselectivity under mild conditions, demonstrating remarkable potential for late-stage functionalization applications. Through comprehensive Density Functional Theory (DFT) studies, we have elucidated the critical role of DPEphos ligand in facilitating the internal hydrosilylation of *gem*-difluoroallenes, offering mechanistic insights into the control of reaction selectivity. This novel approach to selective *gem*-difluoroallene transformation enables the synthesis of previously inaccessible *gem*-difluorovinylsilanes, which serve as versatile building blocks for diverse chemical transformations.

INTRODUCTION

The fluorine atom is considered to significantly alter the physicochemical properties of drug molecules due to its high electronegativity and small size.¹ Additionally, the introduction of fluorine-containing groups could enhance the lipophilicity, metabolic stability, and membrane permeability of the molecules, thereby improving their efficacy and pharmacokinetic properties.² In recent years, gem-difluoroalkenes have attracted much attention in the field of medicinal chemistry³ as a bioisostere of carbonyl group, which could effectively improve the metabolic stability of molecules and optimize the biological activity by modulating the electronic properties of the target binding sites.⁴ For instance, the replacement of the carbonyl group in the artemisinin molecule by a gem-difluoroalkene moiety significantly enhanced the antimalarial activity, suggested that its structure showed effects on the interaction of the molecule with the biological targets based on the adjustment of the electronic distribution and spatial conformation. Furthermore, the gem-difluoroalkene moiety exhibited unique electronic properties, and could be employed in the regulation of the lipophilicity and metabolic stability of molecules, alongside the design of more selective targeted drugs making it a versatile module in drug design (Scheme 1A).⁵

Different from the typical allenes, gem-difluoroallenes possessed the unique backbone of 1,2-propadiene with two fluorine atoms at the terminal position. The electron-withdrawing effect of fluorine atoms showed significant effects on the reactivity of gem-difluoroallenes.⁶ Moreover, due to its high electronegativity and strong C-F bond, the electrophilic α-carbon is more favorable to react with nucleophilic reagents. Although fluorine is not generally considered as a good leaving group, it can often be easily dissociated from gem-difluorinated olefins or activated alkyl fluoride groups under strongly nucleophilic or alkaline conditions.⁷ Compared with the α- and γ-selective addition to gem-difluoroallene, β-addition reactions are relatively
rare. In 2022, Shi's group reported the selective β-addition of thiols to gem-difluoroallenes by a rhodium catalyst, in which the β-adducts were obtained in fair to good yields (58-77%) with high chemo- and regioselectivity (up to 20:1 *rr*) leading to thioenolether with difluoromethyl group in allylic position.⁸ It was revealed by mechanistic studies that the reaction proceeded through a stable Z-rhodacyclic transition state, which enabled the precise control over β-selectivity. However, to our knowledge, this is the only example reported achieving β-additions on gem-difluoroallenes and no example leading to gem-difluorovinyl products has been reported so far.⁹

<figure><img src="image_2.png" /><figcaption>**Scheme 1. Regioselective functionalization of gem-difluoroallenes**</figcaption></figure>
Although numerous studies have documented the addition reactions of various hydrogen-functionalized compounds (e.g., C–H, N–H, O–H, S–H, and P–H bonds) to gem-difluoroallenes (Scheme 1B),¹⁰⁻¹³ the hydrosilylation of gem-difluoroallenes remains unexplored. Notably, existing methods predominantly afford α-functionalized products, whereas regioselective β-position addition to access gem-difluorovinyl compounds remains a significant challenge. Additionally, while hydrosilylation reactions of terminal alkenes are well-developed,¹⁴ the corresponding transformations of internal alkenes are far less explored. This discrepancy arises from the higher reactivity and lower steric hindrance of terminal alkenes, which facilitate efficient coordination with metal catalysts and promote hydrosilylation. Moreover, controlling the regioselectivity of internal alkene hydrosilylation remains a critical challenge in this field (Scheme 1C).¹⁵ To the best of our knowledge, only two examples of internal allene hydrosilylation have been reported,¹⁶ in stark contrast to the well-established hydrosilylation of terminal allenes.¹⁷

Herein, we report a palladium-catalyzed chemo- and regioselective hydrosilylation of gem-difluoroallenes, providing efficient access to β-difluorovinylsilanes under mild conditions (Scheme 1D). This method offers a new strategy for constructing difluorovinylsilanes and difluorovinyl-containing organic molecules.

## RESULTS AND DISCUSSION

The gem-difluoroallene (1a) and diphenylsilane (2a) were used as model substrates to optimize the reaction. During the initial screening experiments, Pd(OAc)₂ was employed as the catalyst, with toluene as the solvent at room temperature, in order to evaluate the performance of various ligands. Triphenylphosphine (PPh₃) produced trace amounts of the desired target product 3a (Table 1, entry 1). Notably, the yield showed an increasing trend to 57% with the use of triphenylphosphite (TPP) as the ligand (Table 1, entry 2). In contrast, nitrogen-based bidentate ligand (Bpy), bidentate phosphine ligand (DPPE) and ferrocenyl-based Ligand (DPPF) were ineffective for the desired hydrosilylation (Table 1, entries 3-5). Among other bidentate-phosphine ligands, BINAP resulted in a modest yield of 18% (Table 1, entry 6), while Xantphos showed a slightly better performance with a yield of 32% (Table 1, entry 7). Notably, [2-(diphenylphosphino)phenyl] ether (DPEphos) achieved a higher yield of 64% of the desired gem-difluorovinylsilane 3a (Table 1, entry 8). For further improvement of the yield of this reaction, the effect of solvent, including dichloromethane (DCM), hexane, THF, EtOAc, and 1,4-dioxane were evaluated. It was found that ether-based solvents showed better activity than other solvents, in which the best results were obtained with 1,4-dioxane leading to 98% of NMR yield of the target product (Table 1, entries 9-13). Notably, the product revealed to be unstable during long purification over silica gel column chromatography, requiring rapid purification to achieve high yields. However, once isolated, it remains stable. Additionally, the evaluation of various palladium catalysts was conducted in this study, in which Pd(OAc)₂ showed the best catalytic performance, whereas other palladium catalysts such as Pd₂(dba)₃·CHCl₃, Pd(PPh₃)₄ and PdBr₂ exhibited significantly lower or no activity (Table 1, entries 14-16). Overall, it was demonstrated by the optimization of the catalyst loading that the reaction could be achieved with only 2 mol% of Pd(OAc)₂ and 3 mol% of DPEphos (Table 1, entry 17).

<table><caption>**Table 1. Optimization of the reaction conditions<sup>a</sup>**</caption><thead><tr><th>Entry</th><th>Ligand</th><th>Solvent</th><th>[Pd]</th><th>Yield (%)<sup>c</sup></th></tr></thead><tbody><tr><td>1</td><td>PPh<sub>3</sub></td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>&lt; 10</td></tr><tr><td>2</td><td>TPP</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>57</td></tr><tr><td>3</td><td>Bpy</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>N.D.</td></tr><tr><td>4</td><td>DPPE</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>N.D.</td></tr><tr><td>5</td><td>DPPF</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>N.D.</td></tr></tbody></table>
<table><tr><td>6</td><td>BINAP</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>18</td></tr><tr><td>7</td><td>Xantphos</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>32</td></tr><tr><td>8</td><td>DPEphos</td><td>Toluene</td><td>Pd(OAc)<sub>2</sub></td><td>64</td></tr><tr><td>9</td><td>DPEphos</td><td>DCM</td><td>Pd(OAc)<sub>2</sub></td><td>N.D.</td></tr><tr><td>10</td><td>DPEphos</td><td>Hexane</td><td>Pd(OAc)<sub>2</sub></td><td>23</td></tr><tr><td>11</td><td>DPEphos</td><td>THF</td><td>Pd(OAc)<sub>2</sub></td><td>64</td></tr><tr><td>12</td><td>DPEphos</td><td>EtOAc</td><td>Pd(OAc)<sub>2</sub></td><td>71</td></tr><tr><td>13</td><td>DPEphos</td><td>1,4-dioxane</td><td>Pd(OAc)<sub>2</sub></td><td>98</td></tr><tr><td>14</td><td>DPEphos</td><td>1,4-dioxane</td><td>Pd<sub>2</sub>(dba)<sub>3</sub>, CHCl<sub>3</sub></td><td>56</td></tr><tr><td>15</td><td>DPEphos</td><td>1,4-dioxane</td><td>Pd(PPh<sub>3</sub>)<sub>4</sub></td><td>N.D.</td></tr><tr><td>16</td><td>DPEphos</td><td>1,4-dioxane</td><td>PdBr<sub>2</sub></td><td>N.D.</td></tr><tr><td>17</td><td>DPEphos<sup>b</sup></td><td>1,4-dioxane</td><td>Pd(OAc)<sub>2</sub><sup>b</sup></td><td>98 (88<sup>d</sup>)</td></tr></table>

<figure><img src="image_3.png" /></figure>

<sup>a</sup> Substrate **1a** (0.2 mmol, 1.0 equiv.), Ph<sub>2</sub>SiH<sub>2</sub> (1.2 equiv, 0.24 mmol), palladium (10 mol%, 0.02 mmol), ligand (12 mol%, 0.024 mmol), solvent (2 mL) at room temperature under Ar for 12 h. <sup>b</sup>Pd(OAc)<sub>2</sub> (2 mol%, 0.004 mmol), DPEphos (3 mol%, 0.006 mmol). <sup>c</sup>Yield was determined by <sup>1</sup>H NMR analysis with CH<sub>2</sub>Br<sub>2</sub> as the internal standard. <sup>d</sup>Isolated yield. N.D. = not determined.

The substrate scope of gem-difluoroallenes (**1a**) with various silanes (**2a-k**) was then investigated under the optimized reaction conditions (Scheme 2). The results showed that a range of diarylsilanes efficiently reacted with gem-difluoroallenes in the current system, exhibiting excellent chemo- and regioselectivity and yielding products **3** in moderate to excellent yields. The scope was composed of diarylsilanes with neutral substituents (**2a**), electron-donating substituents (**2b-e**), and halogen atom (**2f**) leading to corresponding products **3a-f** with yields ranging from 56 to 90%. Arylalkylsilanes with different alkyl groups, such as methyl (**2g**), CH<sub>2</sub> TMS (**2h**), and tert-butyl (**2i**, **2j**), could also afford the target products **3g-j** in high yields, indicating that increased steric hindrance showed no significant effects on the reaction yield and β-selectivity. Notably, the relatively lower isolated yields observed for certain arylalkylsilanes (**2g-2j**) are likely due to the instability of the corresponding hydrosilylation products on silica gel, which can lead to partial desilylation during purification. In contrast, products derived from diarylsilanes exhibited higher stability under the same conditions, thus enabling better yields after chromatographic separation. This observation highlights the different behaviors of arylalkyl- and diarylsilanes in the reaction and purification processes. Additionally, phenylsilane **2k** also showed good activity within this reaction delivering the corresponding product **3k** in 52% yield. Besides, under conditions involving excess PhSiH<sub>3</sub>, the bis-hydrosilylation product (**3l**) was successfully obtained, and the mono-hydrosilylation product (**3k**) was not detected. This experiment indicates distinct differences in reactivity among different hydrosilanes and suggests a sequential addition process.
<figure><img src="image_4.png" /><figcaption>Scheme 2. Scope of hydrosilanes for the catalytic hydrosilylation of gem-difluoroallene 1a.</figcaption></figure>

a Reaction conditions: gem-difluoroallene **1a** (0.2 mmol, 1.0 equiv.), silane (1.2 equiv, 0.24 mmol), Pd(OAc)₂ (2 mol%, 0.004 mmol), DPEphos (3 mol%, 0.006 mmol), 1,4-dioxane (2 mL) at room temperature under Ar for 12 h. **b** **1a** (2.5 equiv, 0.5 mmol), silane (1.0 equiv, 0.2 mmol), Pd(OAc)₂ (5 mol%, 0.01 mmol), DPEphos (10 mol%, 0.02 mmol).

Moreover, the scope was further expanded to gem-difluoroallenes (Scheme 3) containing different aryl (R = 4-Me, 2-F, 4-Cl, 4-Br, 3-CF₃). They exhibited good reactivity with diarylsilanes and provide the target products 3m-3q with 69%-88% yields and excellent chemo- and regioselectivity. Additionally, a substrate with -OBn substituents also showed good tolerance under these experimental conditions with phenyl tert-butylsilane furnishing the corresponding product 3t in fair 50% yield. Regarding the disubstituted aryl substrates (2,4-Cl₂, 3,4-Me₂), the reaction yielded 3r and 3s products with 52% and 82% yields, respectively, and the more polar substituents (-OMe, -CO₂Me,) were also well-tolerated leading to the products 3u and 3v in 76% and 79% yields, respectively.

<caption>Scheme 3. Scope of gem-difluoroallenes for the catalytic hydrosilylation.</caption>
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gem-Difluoroallenes Scope

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gem-Difluoroallenes containing heterocycles (furan, thiophene, 2,3-dioxane) exhibited good to excellent reactivity under this reaction conditions leading to the corresponding products **3w-3y** in yields ranging from 71 to 92%. Furthermore, substrates containing chlorine, *tert*-butyldiphenylsilyl (TBDP) ether terminal alkenes, and long alkyl chains also reacted successfully furnishing the corresponding products **3z-3ac**, with yields ranging from 62% to 74%. Notably, tetrasubstituted gem-difluoroallene also showed high efficiency in the reaction, with the target product **3ad** obtained in 81% yield, albeit without diastereoselectivity (*dr* value of 1:1). The broad substrate compatibility and excellent regioselectivity were demonstrated in this reaction system based on the above results, which could effectively accommodate various silanes and gem-difluoroallenes and it could provide an efficient synthetic strategy for the construction of functionalized silanes and complex organic molecules. Additionally, these findings could further highlight the potential applications of this reaction and provide valuable insights into the development of gem-difluorovinyl chemistry. To further demonstrate the viability of our reaction, gem-difluoroallene from citronellal was successfully employed in this study, and the product **3ae** was obtained in 92% yield with complete regioselectivity.

<footnote>ᵃReaction conditions: gem-difluoroallene (0.2 mmol, 1.0 equiv.), silane (1.2 equiv, 0.24 mmol), Pd(OAc)₂ (2 mol%, 0.004 mmol), DPEphos (3 mol%, 0.006 mmol), 1,4-dioxane (2 mL) at room temperature under Ar for 12 h. ᵇTime = 36 h.</footnote>
<figure><img src="image_25.png" /><figcaption>Scheme 4. Control experiments: A) Gram scale synthesis and further transformation. B) Comparison with non-fluorinated allene. C) Deuterium labeling experiments. D) One-pot competition KIE experiment.</figcaption></figure>

Gram-scale reactions of substrate **1a** were successfully conducted with diphenylsilane **2a** and phenylsilane **2k** provided 1.12 g of product **3a** (60% yield) and 0.87 g of product **3k** (60% yield) with maintained high chemo- and regio-selectivity. We further employed these both products to demonstrate the versatile transformation potential of the *gem*-difluorovinylsilanes. From **3a**, hydrogenation under Pd/C in THF/H₂O as solvent afforded silanol **4** in 90% yield, while methanol as solvent afforded silyl ether **5** in 92% yield. Additionally, treatment with CH₂I₂/Et₂Zn produced alkyl-substituted silane **6** with 70% yield. The hydrosilylation of diphenylacetylene under Pd(OAc)₂/PPh₃ catalysis with **3k** afforded vinylation product **7** in 72% yield. Besides, cyclization of **3k** with 1,4-butanediol under Cs₂CO₃ catalysis formed cyclic dioxasilolane **8** in 75% yield (Scheme 4A). Critical insights were revealed by mechanistic investigation in this study. The comparison between branched product **9** from non-fluorinated allene and our difluoroallene products **3** could suggest that the fluorine's electron-withdrawing effect governed the regiocontrol of the reaction (Scheme 4B). A deuterium labeling experiment with substrate **1a** and Ph₂SiD₂ (**2a-D**) demonstrated >99% of D-incorporation in vinylsilane **3a-D** (Scheme 4C), while kinetic isotope experiments (KIE = 1) seemed to exclude Si-H/D bond cleavage as the rate-determining step (Scheme 4D).

**Scheme 5.** Mechanism of palladium-catalyzed hydrosilylation of *gem*-difluoroallenes. Free-energy profile (ΔG, in kcal·mol⁻¹) for Pd/DPEphos-catalyzed hydrosilylation of difluoroallene (**1a**) with diphenylsilane (**2a**) via four possible pathways (Path 1, 3, 5, 7) calculated at M06L/def2TZVP//M06L/SDD(Pd), 6-31G(d,p) (other elements) level of theory.
<figure><img src="image_26.png" /></figure>

Building upon previous reports of Pd-catalyzed hydrosilylation$^{15j,18}$ and guided by our control experiments, we conducted a systematic mechanistic investigation using density functional theory (DFT) calculations with gem-difluoroallene (1a) and diphenylsilane (2a) as model substrates (Scheme 5). Combining experimental and computational insights, we elucidated the selective formation of the major product 3a in a Pd/DPEphos-catalyzed system. As shown in Scheme 5, the proposed catalytic cycle involves several key steps. Initially, the palladium precursor is reduced in situ by the phosphine ligand to generate the active Pd(0)Ln species (denoted as PdL), which served as the reference point (ΔG = 0) for the Gibbs free energy profile. While palladium typically favors coordination with terminal alkenes, the electron-withdrawing effect of the fluorine substituents in 1a shifts the preference to the internal C₂=C₃ double bond, forming intermediate A. DFT calculations confirmed that coordination at the distal double bond (C₂=C₃) is energetically favored by 11.8 kcal/mol over the proximal C₁=C₂ bond. Subsequent oxidative addition of the Si–H bond in 2a to A yields complex B, which undergoes migratory insertion of the olefin into the Pd–H bond, affording the silyl alkyl Pd(II) intermediate C. Four distinct transition states (TS1-1, TS1-3, TS1-5, and TS1-7) were located along pathways 1, 3, 5, and 7, respectively. This insertion step was identified as the rate-determining step (RDS), critically governing both reactivity and regioselectivity. Comparative analysis of the two competing pathways, as H-insertion versus Si-insertion, revealed that the former consistently exhibits lower activation barriers (see Supporting Information). Finally, reductive elimination from C generates complex D, which releases the product and regenerates PdL to close the catalytic cycle. Energetically, the H-insertion pathway followed by reductive elimination proved most favorable, with TS1-
1 exhibiting the lowest activation barrier (17.6 kcal/mol), consistent with the experimental predominance of 3a. Intriguingly, despite minimal energy differences between TS1-1 and TS1-3, the preferential coordination of Pd to the distal double bond (C2=C3) drives selectivity toward 3a. In contrast, TS1-5 displayed the highest barrier (22.5 kcal/mol), attributed to the electron-withdrawing fluorine substituents, which render the γ-position less nucleophilic by inductively stabilizing a partial positive charge at the α-carbon. Notably, even in the absence of fluorine substituents (e.g., with hydrogen at the α-position), the H-insertion pathway remains energetically favored, though the product distribution shifts to the branched allylic silane 9 (see Supporting Information).

## CONCLUSION

In summary, we have developed a novel palladium-catalyzed β-selective hydrosilylation of gem-difluoroallenes with hydrosilanes, providing efficient access to gem-difluorovinylsilanes. This method exhibits broad substrate scope, delivering the target products in moderate to excellent yields, and demonstrates excellent compatibility with late-stage functionalization strategies. Mechanistic investigations through density functional theory (DFT) calculations revealed the key transition states, offering fundamental insights into the origin of the observed chemo- and regioselectivity. Given the mild reaction conditions and operational simplicity of this protocol, the resulting β-difluorovinylsilanes and their derivatives hold significant potential for diverse applications in synthetic chemistry and pharmaceutical research.

## METHODS

**General Procedure for the synthesis of gem-difluoroallenes 1.** To a solution of $(i-Pr)_2NH$ (20 mmol) in THF (10 mL) was added n-BuLi (20.0 mmol) over 10 min at 0 °C under argon. The resulting solution was allowed to stir for an additional 15 min, and then cooled to -80 °C in a cold ethanol bath. To the cold LDA solution was added a solution of $CF_3CH_2I$ (10.0 mmol) in THF (5 mL) over 10 min, keeping the temperature between -93 °C and -85 °C. After the mixture was stirred for 20 min at that same temperature, a solution of aldehyde (10.0 mmol) in THF (5 mL) was added over 5 min, keeping the temperature between -93 °C and -85 °C. The mixture was stirred for an additional 30 min, then warmed to -30 °C over 90 min. After $Ac_2O$ (12.0 mmol) was added, the mixture was allowed to warm to 0 °C over 2 h. The reaction was quenched with sat. aq $NH_4Cl$ (20 mL), and the products were extracted with ethyl acetate ($3 \times 20$ mL). The combined organic layer was washed with brine (20 mL) and dried ($Na_2SO_4$). After the solvent was removed under reduced pressure, the residue was purified by flash column chromatography giving the acetate S1 (See Supplementary information). To a suspension of zinc powder (17.0 mmol) in DMF (26 mL) was added a solution of S1 (8.50 mmol) in DMF (17 mL) at room temperature under argon, and the mixture was stirred for 3 h. The resulting mixture was filtered to remove the excess zinc and then diluted with ethyl acetate (20 mL) and brine (15 mL). The products were extracted with ethyl acetate ($3 \times 15$ mL). The combined organic layer was washed with brine (15 mL) and dried ($Na_2SO_4$). After the solvent was removed under reduced pressure, the residue was purified by flash column chromatography (pentane) to give 1.

**General Procedure for the synthesis of gem-difluorovinylsilanes 3.** The Schlenk tube was purged with argon for three times, and the tube was added $Pd(OAc)_2$ (0.9 mg, 2 mol%), DPEphos (3.2 mg, 3 mol%), and 1,4-dioxane (2 mL) under argon atmosphere. Then, 1,1-difluoroallene 1 (0.2 mmol, 1.0 equiv.), and silane 2 (0.24 mmol, 1.2 equiv) was added subsequently. The reaction mixture was stirred at room temperature for 12 hours. The resulted mixture was concentrated under reduced pressure and the residue was purified by flash column chromatography on silica gel to afford the difluorovinylsilanes 3.

**General Procedure for the synthesis of (1,1-Difluoro-5-phenylpent-1-en-2-yl)diphenylsilanol 4.** To a solution of 3a (72.8 mg, 0.2 mmol) in THF (2.0 mL, containing 1% v/v $H_2O$) was added to a flame dried Schlenk tube under argon, $Pd/C$ (15.0 mg, 10 wt%) was added and stirred at room temperature. After the reaction was complete (10 min), DCM (5.0 mL) was added and dried by $Na_2SO_4$, then the reaction mixture was filtered through a pad of celite, eluted with ethyl acetate, concentrated in vacuo and purified by silica gel chromatography (Pentane:EA = 100/0 to 95/5) to give the product 4.

**General Procedure for the synthesis of (1,1-difluoro-5-phenylpent-1-en-2-yl)(methoxy)diphenylsilane 5.** To solution of 3a (72.8 mg, 0.2 mmol) in MeOH (2.0 mL) was added to a flame dried Schlenk tube under argon, $Pd/C$ (15.0 mg, 10 wt%) was added and stirred at room temperature. After the reaction was completed, DCM (5.0 mL) was added and dried by $Na_2SO_4$, then the reaction mixture was filtered through a pad of celite, eluted with ethyl acetate, concentrated in vacuo and purified by silica gel chromatography (Pentane:EA = 100/0 to 98/2) to give the product 5.
**General Procedure for the synthesis of (1,1-difluoro-5-phenylpent-1-en-2-yl)(methyl)diphenylsilane 6.**
To a solution of 3a (72.8 mg, 0.2 mmol) in DCE (2.0 mL) was added to a flame dried Schlenk tube under argon, CH₂I₂ (16.0 eq, 3.2 mmol) and Et₂Zn (8.0 eq, 1.6 mmol) was added and stirred at room temperature. After the reaction was complete, DCM (5.0 mL) was added and dried by Na₂SO₄, then the reaction mixture was filtered through a pad of celite, eluted with ethyl acetate, concentrated in vacuo and purified by silica gel chromatography to give the product 6.

**General Procedure for the synthesis of (E)-(1,1-Difluoro-5-phenylpent-1-en-2-yl)(1,2-diphenylvinyl)(phenyl)silane 7.**
In a flame dried Schlenk tube, Pd(OAc)₂ (0.9 mg, 2 mol%), PPh₃ (2.1 mg, 4 mol%) in cyclohexane (1 mL, 0.2 M). Then, 3k (57.7 mg, 0.2 mmol), diphenylacetylene (45.2mg, 0.2 mmol) were added sequentially to the reaction mixture, and the reaction tube was cooled at room temperature and then stirred for 12 h. After completion of the reaction, the mixture was passed through a short celite pad using DCM as a solvent. The residue was purified by column chromatography on silica gel to afford the corresponding product 7 as a colorless oil.

**General Procedure for the synthesis of 2-(1,1-Difluoro-5-phenylpent-1-en-2-yl)-2-phenyl-1,3,2-dioxasilepane 8.**
Inside a nitrogen-atmosphere glovebox, Cs₂CO₃ (0.02 mmol, 10 mol%, 6.6 mg) was charged into an oven-dried 10 mL Schlenk tube equipped with a stirring bar. The reaction tube was capped tightly, and removed from the glovebox. Subsequently, silane 3k (0.2 mmol, 1.0 equiv, 57.7 mg) and 1,4-butanediol (0.24 mmol, 1.2 equiv, 43.2 mg) and THF (3.0 mL) was added under argon atmosphere and then stirred at room temperature for 3 h. Then the mixture was diluted and extracted with DCM. The organic layer was washed with brine, dried with anhydrous Na₂SO₄, filtered and concentrated in vacuo. The residue was purified by column chromatography on silica gel to afford the corresponding product 8 as a colorless oil.

**General Procedure for the synthesis of diphenyl(5-phenylpent-1-en-3-yl)silane 9.**
The Schlenk tube was purged with argon for three times, and the tube was added Pd(OAc)₂ (0.9 mg, 2 mol%), DPEphos (3.2 mg, 3 mol%), and 1,4-dioxane (2 mL) under argon atmosphere. Then, allene (0.2 mmol, 1.0 equiv.), and Ph₂SiH₂ (0.24 mmol, 1.2 equiv) was added subsequently. The reaction mixture was stirred at room temperature for 12 hours. The resulted mixture was concentrated under reduced pressure and the residue was purified by flash column chromatography on silica gel to afford the difluorovinylsilanes 9.

# AUTHOR INFORMATION

## Corresponding Author

Samuel Couve-Bonnaire-Univ. Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ., Institut CARMeN UMR 6064, F-76000 Rouen, France; orcid.org/0000-0003-2149-0849; Email: samuel.couve-bonnaire@insa-rouen.fr

Li-Wen Xu-Hangzhou Normal University, Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, 311121 Hangzhou, P. R. China; orcid.org/0000-0001-5705-0015; Email: liwenxu@hznu.edu.cn

Jean-Philippe Bouillon-Univ. Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ., Institut CARMeN UMR 6064, F-76000 Rouen, France; orcid.org/0000-0002-6247-1125; Email: jean-philippe.bouillon@univ-rouen.fr

## Author

Xin-Long Yu-Univ. Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ., Institut CARMeN UMR 6064, F-76000 Rouen, France

An-Jiu Wen-Hangzhou Normal University, Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, 311121 Hangzhou, P. R. China

Zheng Xu-Hangzhou Normal University, Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, 311121 Hangzhou, P. R. China

## Author Contributions

The manuscript was written through contributions of all authors. All the authors have given approval to the final version of the manuscript.

# ASSOCIATED CONTENT

The data underlying this study are available in the published article and its online Supporting Information. Reaction optimization, experimental procedures, characterization data, copies of ¹H, ¹³C, ¹⁹F spectra (PDF).
## Funding Sources

This work was supported by the Normandie Université (NU), the Région Normandie, the Centre National de la Recherche Scientifique (CNRS), Université de Rouen Normandie (URN), INSA Rouen Normandie, Labex SynOrg (ANR-11-LABX-0029), the Graduate School for Research XL-Chem (ANR-18-EURE-0020 XL CHEM), and Innovation Chimie Carnot (I2C). National Natural Science Foundation of China (No. 22371060 and 22361162606), Zhejiang Provincial Natural Science Foundation of China (No. LZ23B020002), and Interdisciplinary Research Project of Hangzhou Normal University (2025JCXK02) are gratefully acknowledged.

## Notes

The authors declare no competing financial interests.

## ACKNOWLEDGMENT

X.-L.Y. thanks the Région Normandie (RIN 50% program) for a doctoral fellowship. The authors also thank Dr. J. Cao and Dr. J.H. Ma for their assistance on the spectral analysis.

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