Visible Light-Driven Radical trans-Hydrosilylation of Electron-Neutral

Oct 31, 2018 - A visible light-driven radical hydrosilylation of electron-neutral and -rich alkenes has been investigated on the basis of a newly deve...
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Visible Light-Driven Radical trans-Hydrosilylation of ElectronNeutral and -Rich Alkenes with Tertiary and Secondary Hydrosilanes Jing Zhu, Wei-Chen Cui, Shaozhong Wang,* and Zhu-Jun Yao* State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, Jiangsu 210023, China

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S Supporting Information *

ABSTRACT: A visible light-driven radical hydrosilylation of electron-neutral and -rich alkenes has been investigated on the basis of a newly developed catalytic reaction system composed of eosin Y, thiol, and base additives. A variety of linear and cyclic alkenes with different substitution patterns were found to undergo such metal-free hydrosilylation with tertiary and secondary hydrosilanes in a chemo-, regio-, and stereoselective manner. Comparison of the reactivity of diene compounds and late-stage hydrosilylation of steroid drugs were also explored. Deuterium labeling experiments reveal that a stepwise formation of C−Si and C−H bonds with a trans stereochemistry is preferred, in which the thiol may behave as a hydrogen atom transfer agent.

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INTRODUCTION Radical hydrosilylation of alkenes involves an anti-Markovnikovtype addition of a silyl radical across a carboncarbon bond and the straightforward formation of a carbon−silicon bond.1 Although certain applications of this highly atom-economic transformation were found in synthetic chemistry2 and material chemistry,3 in which various silicon-containing groups and alkyl fragments derived from alkenes were joined together, issues such as the scope of alkenes and hydrosilanes and functional group compatibility are still encountered. At an early stage, a type of radical-chain hydrosilylation of alkene was thoroughly investigated (Scheme 1a).2a−d Two

hydrogen atom transfers (HAT) among a hydrosilane, an extra electrophilic radical species [Me•, F3C•, Cl3C•, PhC(O)O•, and t BuO•], and a silylated carbon-centered radical were supposed.4 To ensure the HAT from the hydrosilane to the radical adduct, labile trichlorosilane or bulky tris(trimethylsilyl)silane with a weaker Si−H bond was preferred over normal tertiary and secondary ones.5 Later, Roberts advanced a polarity-reversal catalysis to nicely solve the mismatch between the nucleophilic silylated carbon-centered radical and the hydridic hydrosilane.2e,f The introduction of thiol as a hydrogen transfer agent significantly put forward the radical hydrosilylation of alkenes.6,7 Furthermore, a combination of polarity-reversal catalysis and photocatalysis invented by Wu and co-workers enabled a hydrosilylation of monosubstituted electron-rich alkenes with a variety of hydrosilanes (Scheme 1b).2k Our recent experience in radical hydrosilylation of alkynes encouraged us to reinvestigate the alkene hydrosilylation by using a commercially available organic dye as a photocatalyst,8,9 with the aim of extending the scope from terminal alkenes to multisubstituted alkenes, discriminating the relative reactivity between terminal alkenes and internal alkenes, and attempting late-stage hydrosilylation of alkene-containing pharmaceutically relevant molecules (Scheme 1c).

Scheme 1. Radical Hydrosilylation of Electron-Neutral and -Rich Alkenes

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RESULTS AND DISCUSSION Initially, we chose 4-pentenyl acetate and triphenylsilane as model compounds to study hydrosilylation. A few commercially available organic dyes, including rhodamine 6G (Rh 6G), rhodamine B (Rh B), eosin Y (EY), and rose bengal (RB), were selected as photocatalysts (PCs) (Table 1, entries 1−4, Received: September 18, 2018 Published: October 31, 2018 © XXXX American Chemical Society

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DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry Table 1. Optimization of the Radical Hydrosilylationa

a

Reaction conditions: 0.3 mmol of alkene, 0.36 mmol of hydrosilane, 5 mol % PC, 20 mol % thiol, 20 mol % base, 3.0 mL of a degassed dioxane/ H2O mixture (50/1, v/v), 10 W white LEDs, 32−34 °C. bNMR yield using 1,3,5-trimethoxybenzene as an internal standard. cHere 1 mol % EY, 5 mol % thiol I, and 5 mol % K2CO3 were used.

respectively). Under the irradiation of a 10 W white lightemitting diode (LED) and with the assistance of base and thiol additives, the expected hydrosilylation occurred in a mixed solvent of dioxane and water (50/1, v/v). A combination of eosin Y (2 mol %), potassium carbonate (20 mol %), and triisopropylsilanethiol10 (20 mol %) gave anti-Markovnikov adduct 1 in 99% yield. Other thiol additives such as 2methylpropane-2-thiol and ethyl 2-mercaptopropanoate resulted in lower yields (Table 1, entries 5 and 6, respectively).11,12 No adduct was captured by using 2,4,6-triisopropylbenzenethiol (Table 1, entry 7). A slightly decreased yield was observed when K2HPO4 or Na2CO3 was used instead of K2CO3 (Table 1, entry 8 or 9, respectively). In the absence of base additives, incomplete conversion was found (Table 1, entry 10). The reaction worked perfectly even when the loadings of eosin Y, potassium carbonate, and thiol I were decreased (Table 1, entry 11). Control experiments (see the Supporting Information) revealed that (1) the ratio between triphenylsilane and the alkene is essential for a complete conversion, (2) no adduct was detected in the absence of either a photocatalyst or a thiol additive, and (3) no reaction took place without irradiation.

With optimized conditions in hand, we next sought to examine the scope of the visible light-driven hydrosilylation. As illustrated in Table 2, a set of monosubstituted and 1,1′disubstituted electron-neutral alkenes containing cyclohexyl, alkoxyl, and tert-butyl substituents reacted with triphenylsilane smoothly, giving adducts 2−4 in moderate to excellent yields. Electron-rich alkenes, including vinyl sulfane, vinyl phosphine, and vinyl ethers, proved to be competent partners for the hydrosilylation protocol, delivering adducts 5−10 in yields of 55−96%. The variation of yield suggested that the nature of the heteroatoms and the steric effect of the attached alkyl substituents may affect the transformation. Under an identical condition, vinyl acetate was converted to 11 in 91% yield. Parallel experiments revealed that a series of tertiary hydrosilanes, including Ph 2 MeSiH, PhMe 2 SiH, Et 3 SiH, and (TMS)3SiH reacted, with vinyl acetate to afford 12−15, respectively. The yield varied depending on the Si−H bond dissociation energy in different hydrosilanes.13 Both the arylated hydrosilanes and (TMS)3SiH are favorable for conversion. A poor yield was obtained in the case of Et3SiH. Except for the tertiary hydrosilanes, the secondary hydrosilane Ph2SiH2 may B

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry Table 2. Radical Hydrosilylation of Terminal Alkenesa

a

Reaction conditions: 0.3 mmol of alkene, 0.36 mmol of hydrosilane, 1 mol % EY, 5 mol % thiol I, 5 mol % K2CO3, 3.0 mL of a degassed dioxane/ H2O mixture (50/1, v/v), 10 W white LEDs, 32−34 °C. bWith 50 W white LEDs and 3.0 mL of a degassed dioxane/H2O mixture (100/1, v/v) instead.

engage in the hydrosilylation, affording adducts 16 and 17 bearing a Si−H bond. The hydrosilylation of internal alkenes was further explored, which was viewed as being more easily challenged than that of terminal alkenes. The increasing steric effect may cause a slower silyl radical addition to the carboncarbon bond.14,15 We first attempted to react an array of symmetrical cyclic alkenes with different ring sizes with a secondary hydrosilane (Ph2SiH2) (Table 3). To our delight, cycloalkylated silanes 18−23 were obtained in yields of 31−91% under an improved condition. As compared with normal cyclic alkenes (cyclopentene, cyclohexene, and cycloheptene), middle-sized cyclooctene and bicyclic norbornene with higher ring tension displayed better reactivity. The cyclic enol ether and enol acetate containing an electron-rich double bond participated in the hydrosilylation in a similar manner, giving adducts 24 and 25 in which a silyl group is located at the β-position toward the oxygen atom. The protocol was applicable for the linear alkenes. However, the configuration of the double bond is critical. As evidenced by the reaction outcomes of hex-3-enes, the Z isomer gave 26 in a yield higher than that of the E isomer. Furthermore, when β-citronellol, an unsymmetrical trisubstituted internal alkene, was examined, adduct 27 was isolated in 59% yield. Although the diastereoselectivity of 27 was poor, excellent regioselectivity was indeed obtained and no other regioisomer was captured. To our disappointment, fully substituted alkenes failed in the hydrosilylation at this stage.

To probe the relative reactivity between a terminal alkene and an internal alkene, an array of diene substrates containing at least one terminal alkene were attempted (Table 4). Although a detectable hydrosilylation of cyclic alkene in limonene was found, the hydrosilylation of exocyclic 1,1′-disubstituted terminal alkene was more favorable than that of trisubstituted cyclohexene (Table 4, entry 1). A similar regioselectivity was observed in the case of nootkatone (Table 4, entry 2). Adducts 29 and 30 were isolated as major products with 1/1 diastereoselectivity. No hydrosilylation of 1,2-disubstituted cyclic alkene was detected when a vinyl-substituted cyclohexene was attempted, leading to the formation of adduct 31 in 44% yield (Table 4, entry 3). The hydrosilylation of an (E)-1,2disubstituted linear alkene also did not compete with that of a monosubstituted one, giving 33 exclusively in 62% yield (Table 4, entry 4). The comparable reactivity of a 1,1-disubstituted alkene and a monosubstituted alkene was found, providing three possible adducts, 33−35 (Table 4, entry 5). To discern in detail the mechanism of the hydrosilylation, a series of deuterium labeling experiments based on the reaction of triphenylsilane and a terminal alkene were performed (Scheme 2a). Less than 1% deuterium atom was detected in adduct 36 when 1,4-dioxane-d8 was applied as a solvent, which excluded the possibility that the solvent attended the reaction as the hydrogen source (Scheme 2b). Approximately 15% incorporation of deuterium was detected when Ph3SiD was utilized (Scheme 2c). Almost the same deuterium content was C

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry Table 3. Radical Hydrosilylation of Internal Alkenesa

hydrosilylation adduct and the thiyl radical (E1/2red = −0.82 V vs the SCE in MeCN),2k which is easily reduced by radical anion EY•− [E1/2(EY/EY−) = −1.06 V vs the SCE in MeCN]18 and combined by a proton to regenerate the thiol. The thiol plays dual roles in the transformation as both a hydrogen abstractor at the radical initiation step and a hydrogen donor at the radical quenching step. As evidenced by the deuterium labeling experiment, the thiol is prone to approach to the silylated carbon-centered radical in an energetically beneficial manner because of the steric interference, which forces the newly formed C−H bond to be located at the trans position of the C−Si bond. To demonstrate the synthetic utility of the transformation, two clinical drugs, pregnenolone acetate and stigmasterol, containing a multisubstituted cyclohexene ring were assessed (Scheme 4). As shown, both of them underwent the visible lightdriven hydrosilylation to give adducts 37 and 38 in a highly chemo-, regio-, and diastereoselective manner. A range of functional groups such as ester, ketone, free hydroxy, and exocyclic 1,2-disubstituted alkene remained undisturbed. The stereochemistry of the newly formed C−Si and C−H bonds was established by NMR experiments. This late-stage hydrosilylation is supposed to provide a potential route for the rapid generation of silicon-containing medicinally relevant molecules.

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CONCLUSION A mild visible light-driven radical hydrosilylation of alkenes has been achieved using catalytic amounts of eosin Y as the photocatalyst, thiol, and base additives. A variety of mono-, di-, and trisubstituted linear and cyclic electron-neutral and -rich alkenes have been examined and found to undergo the chemo-, regio-, and stereoselective hydrosilylation with either tertiary or secondary hydrosilanes. The relative reactivity, especially between a terminal alkene and an internal alkene, and the latestage hydrosilylation of two steroid drugs were explored. Deuterium labeling experiments further suggested that a stepwise formation of a C−Si bond and a C−H bond with a trans stereochemistry is preferred, in which the thiol acts as a polarity-reversal agent. Further applications of the radical hydrosilylation of alkenes are expected.

a

Reaction conditions: 0.3 mmol of alkene, 0.36 mmol of hydrosilane, 1 mol % EY, 5 mol % thiol I, 5 mol % K2CO3, 3.0 mL of a degassed dioxane/H2O mixture (100/1, v/v), 50 W white LEDs, 36−38 °C.

found when D2O was used in place of water (Scheme 2d). Meanwhile, a hydrogen/deuterium exchange between the deuterated hydrosilane and water was encountered in the investigation (see the Supporting Information),16 which made us hypothesize that the new hydrogen in the adduct may originate from water. The hypothesis was further supported by the fact that ≤81% deuterium atom was incorporated when the amount of D2O was improved significantly, even though the isotope effect made the yield decrease to 19% (Scheme 2e,f). To identify the relative stereochemistry of the hydrogen and the silyl group in the adduct, a diester-substituted cyclopentene and diphenylhydrosilane were subjected to a reaction system containing excess D2O as shown in Scheme 2e, and the adduct was eventually isolated with 77% deuterium incorporation after a 48 h irradiation under 50 W white LEDs (Scheme 2g). The NMR analyses confirmed undoubtedly that the deuterium atom is located in an axial position that is away from the equatorial silyl group, highlighting a possible stepwise trans-hydrosilylation of alkenes. A proposed catalytic cycle is outlined in Scheme 3. The excited state EY* is generated from EY by visible light irradiation. Under the assistance of the base additive, a proton-coupled electron transfer (PCET) process [E1/2(*EY/ EY−) = 0.83 V vs the saturated calomel electrode (SCE); thiol I E1/2ox = 0.28 V vs the SCE]2k,17,18 may happen to deliver a thiyl radical and radical anion EY•−. A subsequent HAT from the hydrosilane to the electrophilic thiyl radical will result in the formation of a silyl radical [the bond dissociation energy (BDE) value of the Si−H bond in Ph3SiH is ∼86.4 kcal/mol, and the BDE value of the S−H bond in thiol I is 88.2 kcal/mol].13 The silyl radical further reacts with an alkene to generate a siliconstabilized carbon-centered radical. Another HAT from the thiol to the nucleophilic carbon-centered radical will deliver the

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EXPERIMENTAL SECTION

General Information. All melting points were determined without correction. 1H NMR spectra were obtained at 400 MHz, and 13C NMR spectra were obtained at 101 MHz. Spectra were recorded in a CDCl3 solution using the residual protonated solvent as the internal standard, J values are given in hertz. High-resolution mass spectral analyses (HRMS) were performed on a Q-TOF-MS spectrometer. The 10 W LEDs (model 12 V 5050) with maximum emission at ∼582 nm were purchased from Greenthink Co., Ltd. (China). The 50 white LEDs (model 10E 60P 50W PW) with maximum emission at ∼475 nm were purchased from Qiyiguo Photoelectric Co., Ltd. (China). For the emission spectra of LEDs, see the Supporting Information. General Procedure for the Radical Hydrosilylation of Alkenes. Under a nitrogen atmosphere, to a dry 10 mL glass tube containing eosin Y (2 mg, 0.003 mmol) and K2CO3 (2 mg, 0.015 mmol) were added successively a tertiary or secondary hydrosilane (0.36 or 0.3 mmol), alkene (0.3 mmol), iPr3SiSH (2.8 mg, 0.015 mmol), and a degassed 1,4-dioxane/H2O mixture (3 mL, 50/1 or 100/ 1 v/v) at room temperature. The reaction mixture was stirred and irradiated with white LEDs (10 or 50 W) at a distance of 5 cm. Upon completion (monitored by TLC), the solution was concentrated under vacuum. The residue was further purified by silica gel column chromatography (PE for 2, 4−6, 10, 15, 17, 19−23, 26, 29, 31, and 36; 100/1 PE/EA for 1, 7−9, 11−14, 16, 24, and 32−35; and 10/1 PE/ EA for 3, 18, 25, 27, 30, 37, and 38). D

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry Table 4. Radical Hydrosilylation of Dienesa

a

Reaction conditions: 0.3 mmol of alkene, 0.3 mmol of hydrosilane, 1 mol % EY, 5 mol % thiol I, 5 mol % K2CO3, 3.0 mL of a degassed dioxane/ H2O mixture (100/1, v/v), 50 W white LEDs, 36−38 °C. bAdduct 29 is contaminated with an inseparable minor product, whose structure was

supposed as

. cHere 10 W white LEDs, a dioxane/H2O mixture (50/1, v/v), and 32−34 °C instead. 26.0, 23.4, 21.7; IR (KBr) vmax 2922, 1427, 1107, 698 cm−1; HRMS (ESI) calcd for C23H26NaOSi m/z 369.1645 [M + Na]+, found 369.1644. Triphenyl(2,3,3-trimethylbutyl)silane (4). Colorless oil, 55 mg, 52% yield; 1H NMR (400 MHz, CDCl3) δ 7.66−7.56 (m, 6H), 7.49−7.34 (m, 9H), 1.70 (d, J = 14.8 Hz, 1H), 1.66−1.55 (m, 1H), 1.22−1.11 (m, 1H), 0.89 (d, J = 0.4 Hz, 9H), 0.73 (d, J = 6.8 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 136.0, 129.4, 127.9, 38.9, 34.3, 29.0, 27.2, 17.7, 15.9;IR (KBr) vmax 2958, 1485, 1107, 696 cm−1; HRMS (ESI) calcd for C25H31Si m/z 359.2190 [M + H]+, found 359.2189. Triphenyl[2-(phenylthio)ethyl]silane (5).20 White solid, 67 mg, 57% yield; mp 98−99 °C; 1H NMR (400 MHz, CDCl3) δ 7.61−7.53 (m, 6H), 7.51−7.38 (m, 9H), 7.33−7.26 (m, 4H), 7.24−7.17 (m, 1H), 3.16−3.10 (m, 2H), 1.88−1.82 (m, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.7, 134.1, 129.9, 129.4, 129.0, 128.2, 126.0, 29.4, 14.1; IR (KBr) vmax 2922, 1427, 1110, 697 cm−1; HRMS (ESI) calcd for C26H24NaSSi m/z 419.1260 [M + Na]+, found 419.1255. Diphenyl[2-(triphenylsilyl)ethyl]phosphane (6).21 White solid, 120 mg, 85% yield; mp 134−135 °C; 1H NMR (400 MHz, CDCl3) δ 7.55− 7.50 (m, 6H), 7.48−7.30 (m, 19H), 2.23−2.16 (m, 2H), 1.55−1.44 (m,

5-(Triphenylsilyl)pentyl Acetate (1). White solid, 114 mg, 99% yield; mp 52−53 °C; 1H NMR (400 MHz, CDCl3) δ 7.60−7.53 (m, 6H), 7.46−7.34 (m, 9H), 4.04 (t, J = 6.7 Hz, 2H), 2.04 (s, 3H), 1.69−1.62 (m, 2H), 1.59−1.51 (m, 2H), 1.50−1.39 (m, 4H); 13C{1H} NMR (101 MHz, CDCl3) δ 171.2, 135.7, 135.2, 129.5, 127.9, 64.6, 30.1, 28.3, 23.8, 21.0, 13.3; IR (KBr) vmax 2923, 1738, 1258, 1012, 791, 699 cm−1; HRMS (ESI) calcd for C25H28NaO2Si m/z 411.1751 [M + Na]+, found 411.1746. (2-Cyclohexylethyl)triphenylsilane (2).19 White solid, 86 mg, 78% yield; mp 54−56 °C; 1H NMR (400 MHz, CDCl3) δ 7.61−7.50 (m, 6H), 7.47−7.31 (m, 9H), 1.85−1.73 (m, 2H), 1.74−1.59 (m, 3H), 1.40 (s, 2H), 1.39 (s, 2H), 1.30−1.06 (m, 4H), 0.98−0.76 (m, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.8, 135.6, 129.4, 127.9, 41.0, 33.0, 31.4, 26.9, 26.6, 10.4; IR (KBr) vmax 2920, 1259, 1109, 797, 697 cm−1; HRMS (ESI) calcd for C26H31Si m/z 371.2190 [M + H]+, found 371.2202. 3-Methyl-4-(triphenylsilyl)butan-1-ol (3). Colorless oil, 101 mg, 98% yield; 1H NMR (400 MHz, CDCl3) δ 7.75−7.54 (m, 6H), 7.53− 7.31 (m, 9H), 3.67−3.49 (m, 2H), 2.07−1.92 (m, 1H), 1.66−1.53 (m, 2H), 1.52−1.44 (m, 1H), 1.44−1.36 (m, 1H), 0.93 (d, J = 6.6 Hz, 3H); 13 C{1H} NMR (101 MHz, CDCl3) δ 135.8, 129.5, 128.0, 61.0, 43.4, E

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry Scheme 2. Mechanistic Studies

Scheme 3. Proposed Mechanism

Scheme 4. Radical Hydrosilylation of Steroid Drugs

2H); 13C{1H} NMR (101 MHz, CDCl3) δ 138.6, 138.4, 135.7, 134.6, 133.1, 132.9, 129.7, 128.7, 128.5, 128.5, 128.1, 21.7, 21.6, 8.9, 8.8; IR (KBr) vmax 2922, 1427, 1109, 696 cm−1; HRMS (ESI) calcd for C32H29NaPSi m/z 495.1668 [M + Na]+, found 495.1671. (2-Ethoxyethyl)triphenylsilane (7). White solid, 95 mg, 96% yield; mp 53−54 °C; 1H NMR (400 MHz, CDCl3) δ 7.67−7.52 (m, 6H),

7.51−7.34 (m, 9H), 3.71−3.60 (m, 2H), 3.42 (q, J = 7.0 Hz, 2H), 1.97−1.82 (m, 2H), 1.18 (t, J = 7.0 Hz, 3H); 13C{1H} NMR (101 MHz, F

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

Article

The Journal of Organic Chemistry CDCl3) δ 135.7, 134.8, 129.6, 128.0, 67.3, 65.7, 15.4, 15.4; IR (KBr) vmax 2922, 1258, 1093, 1012, 792, 697 cm−1; HRMS (ESI) calcd for C22H24NaOSi m/z 355.1489 [M + Na]+, found 355.1481. (2-Methoxypropyl)triphenylsilane (8). White solid, 85 mg, 85% yield; mp 58−59 °C; 1H NMR (400 MHz, CDCl3) δ 7.66−7.54 (m, 6H), 7.49−7.33 (m, 9H), 3.56−3.45 (m, 1H), 3.08 (s, 3H), 1.95 (dd, J1 = 14.8, J2 = 7.2 Hz, 1H), 1.62 (dd, J1 = 14.9, J2 = 6.6 Hz, 1H), 1.15 (d, J = 6.0 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.9, 129.4, 127.9, 74.4, 55.5, 22.8, 22.2; IR (KBr) vmax 2923, 1427, 1108, 697 cm−1; HRMS (ESI) calcd for C22H24NaOSi m/z 355.1489 [M + Na]+, found 355.1497. Trimethyl{[1-(triphenylsilyl)propan-2-yl]oxy}silane (9). White solid, 99 mg, 85% yield; mp 46−47 °C; 1H NMR (400 MHz, CDCl3) δ 7.66−7.55 (m, 6H), 7.49−7.34 (m, 9H), 4.19−4.07 (m, 1H), 1.90 (dd, J1 = 14.8 Hz, J2 = 6.6 Hz, 1H), 1.75 (dd, J1 = 14.8 Hz, J2 = 6.9 Hz, 1H), 1.18 (d, J = 6.0 Hz, 3H), −0.05 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ 136.0, 135.5, 129.4, 127.9, 66.5, 27.3, 26.2, 0.3; IR (KBr) vmax 2958, 1427, 1249, 1108, 837, 697 cm−1; HRMS (ESI) calcd for C24H30NaOSi2 m/z 413.1727 [M + Na]+, found 413.1715. {[3,3-Dimethyl-1-(triphenylsilyl)butan-2-yl]oxy}trimethylsilane (10). White solid, 71 mg, 55% yield; mp 107−109 °C; 1H NMR (400 MHz, CDCl3) δ 7.64−7.58 (m, 6H), 7.43−7.34 (m, 9H), 3.75 (dd, J1 = 9.1 Hz, J2 = 3.6 Hz, 1H), 1.85 (dd, J1 = 15.4 Hz, J2 = 9.1 Hz, 1H), 1.70 (dd, J1 = 15.4 Hz, J2 = 3.7 Hz, 1H), 0.90 (s, 9H), −0.30 (s, 9H); 13 C{1H} NMR (101 MHz, CDCl3) δ 136.2, 129.4, 127.8, 78.4, 36.9, 26.6, 18.0, 1.0; IR (KBr) vmax 2924, 1259, 1107, 799, 698 cm−1; HRMS (ESI) calcd for C27H36NaOSi2 m/z 455.2197 [M + Na]+, found 455.2197. 1-(Triphenylsilyl)propan-2-yl Acetate (11).2f White solid, 114 mg, 98% yield; mp 61−62 °C; 1H NMR (400 MHz, CDCl3) δ 7.62 (d, J = 6.4 Hz, 6H), 7.53−7.35 (m, 9H), 5.32−5.16 (m, 1H), 2.09−1.98 (m, 1H), 1.83−1.75 (m, 1H), 1.72 (s, 3H), 1.27 (d, J = 6.1 Hz, 3H); 13 C{1H} NMR (101 MHz, CDCl3) δ 170.4, 135.7, 134.7, 129.6, 128.0, 69.3, 23.6, 22.0, 21.1; IR (KBr) vmax 2937, 1732, 1220, 956, 697 cm−1; HRMS (ESI) calcd for C23H24NaO2Si m/z 383.1438 [M + Na]+, found 383.1432. 1-(Methyldiphenylsilyl)propan-2-yl Acetate (12). Colorless oil, 72 mg, 81% yield; 1H NMR (400 MHz, CDCl3) δ 7.62−7.50 (m, 4H), 7.46−7.32 (m, 6H), 5.22−5.05 (m, 1H), 1.80 (s, 3H), 1.69 (dd, J1 = 14.6 Hz, J2 = 7.4 Hz, 1H), 1.46 (dd, J1 = 14.7 Hz, J2 = 6.9 Hz, 1H), 1.23 (d, J = 6.2 Hz, 3H), 0.66 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 170.5, 136.8, 136.7, 134.5, 134.5, 129.4, 128.0, 128.0, 69.5, 23.4, 23.0, 21.3, −3.7; IR (KBr) vmax 2926, 1730, 1243, 1110, 697 cm−1; HRMS (ESI) calcd for C18H22NaO2Si m/z 321.1281 [M + Na]+, found 321.1278. 1-[Dimethyl(phenyl)silyl]propan-2-yl Acetate (13).7a Colorless oil, 52 mg, 74% yield; 1H NMR (400 MHz, CDCl3) δ 7.59−7.47 (m, 2H), 7.46−7.31 (m, 3H), 5.10−4.99 (m, 1H), 1.89 (s, 3H), 1.32 (dd, J1 = 14.5 Hz, J2 = 7.0 Hz, 1H), 1.21 (d, J = 6.2 Hz, 4H), 1.13 (dd, J1 = 14.5 Hz, J2 = 7.2 Hz, 1H), 0.34 (s, 3H), 0.33 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 170.6, 138.8, 133.6, 129.1, 127.9, 69.8, 24.5, 23.3, 21.5, −2.2; IR (KBr) vmax 2925, 1734, 1246, 1112, 1015, 833, 698 cm−1; HRMS (ESI) calcd for C13H20NaO2Si m/z 259.1125 [M + Na]+, found 259.1121. 1-(Triethylsilyl)propan-2-yl Acetate (14).22 Colorless oil, 26 mg, 41% yield; 1H NMR (400 MHz, CDCl3) δ 5.02 (dd, J1 = 13.6 Hz, J2 = 6.8 Hz, 1H), 1.99 (s, 3H), 1.25 (d, J = 6.1 Hz, 3H), 1.05 (dd, J1 = 14.5 Hz, J2 = 6.9 Hz, 1H), 0.93 (t, J = 7.9 Hz, 9H), 0.86 (dd, J1 = 14.5 Hz, J2 = 7.6 Hz, 1H), 0.53 (q, J = 7.9 Hz, 6H); 13C{1H} NMR (101 MHz, CDCl3) δ 170.7, 70.1, 23.4, 21.7, 20.1, 7.5, 3.9; IR (KBr) vmax 2923, 1738, 1258, 1010, 790 cm−1; HRMS (ESI) calcd for C11H24NaO2Si m/ z 239.1438 [M + Na]+, found 239.1448. 1-[1,1,1,3,3,3-Hexamethyl-2-(trimethylsilyl)trisilan-2-yl]propan2-yl Acetate (15). Colorless oil, 86 mg, 82% yield; 1H NMR (400 MHz, CDCl3) δ 5.04−4.84 (m, 1H), 2.01 (s, 3H), 1.34−1.25 (m, 4H), 1.07 (dd, J = 13.9, 8.3 Hz, 1H), 0.17 (s, 27H); 13C{1H} NMR (101 MHz, CDCl3) δ 170.7, 72.3, 23.0, 21.9, 16.4, 1.3; IR (KBr) vmax 2958, 1738, 1258, 1012, 791 cm−1; HRMS (ESI) calcd for C14H36NaO2Si4 m/z 371.1685 [M + Na]+, found 371.1674.

1-(Diphenylsilyl)propan-2-yl Acetate (16). Colorless oil, 63 mg, 74% yield; 1H NMR (400 MHz, CDCl3) δ 7.68−7.52 (m, 4H), 7.48− 7.32 (m, 6H), 5.21−5.11 (m, 1H), 4.96 (t, J = 3.8 Hz, 1H), 1.84 (s, 3H), 1.77−1.68 (m, 1H), 1.57 (m, 1H), 1.31 (d, J = 6.2 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 170.6, 135.2, 135.1, 133.9, 133.6, 129.9, 129.8, 128.2, 128.2, 69.5, 22.7, 21.1; IR (KBr) vmax 2961, 2127, 1732, 1257, 1013, 795, 698 cm−1; HRMS (ESI) calcd for C17H20NaO2Si m/z 307.1125 [M + Na]+, found 307.1125. tert-Butyl[2-(diphenylsilyl)-1-methoxyethoxy]dimethylsilane (17). Colorless oil, 75 mg, 67% yield; 1H NMR (400 MHz, CDCl3) δ 7.66−7.57 (m, 4H), 7.46−7.35 (m, 6H), 5.00−4.93 (m, 1H), 4.89 (dd, J = 7.0, 4.5 Hz, 1H), 3.24 (s, 3H), 1.79−1.71 (m, 1H), 1.65 (dt, J1 = 14.7 Hz, J2 = 4.3 Hz, 1H), 0.90 (s, 9H), 0.09 (s, 3H), 0.05 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.4, 135.3, 134.5 134.4, 129.6, 128.0, 97.8, 53.5, 25.9, 23.3, 18.2, −4.2, −4.4; IR (KBr) vmax 2926, 1428, 1116, 803, 696 cm−1; HRMS (ESI) calcd for C21H32NaO2Si2 m/z 395.1833 [M + Na]+, found 395.1829. Dimethyl 3-(Diphenylsilyl)cyclopentane-1,1-dicarboxylate (18). Colorless oil, 70 mg, 64% yield; 1H NMR (400 MHz, CDCl3) δ 7.63− 7.53 (m, 4H), 7.45−7.33 (m, 6H), 4.81 (d, J = 3.8 Hz, 1H), 3.73 (s, 3H), 3.67 (s, 3H), 2.67−2.58 (m, 1H), 2.37−2.27 (m, 1H), 2.27−2.17 (m, 1H), 2.11−1.97 (m, 2H), 1.87−1.75 (m, 1H), 1.75−1.65 (m, 1H); 13 C{1H} NMR (101 MHz, CDCl3) δ 173.1, 172.8, 135.4, 135.4, 133.6, 133.5, 129.8, 128.1, 128.1, 61.4, 52.8, 52.7, 38.0, 35.8, 29.0, 23.2; IR (KBr) vmax 2961, 1730, 1256, 698 cm−1; HRMS (ESI) calcd for C21H24NaO4Si m/z 391.1336 [M + Na]+, found 391.1339. Cyclopentyldiphenylsilane (19).23 Colorless oil, 32 mg, 43% yield; 1 H NMR (400 MHz, CDCl3) δ 7.63−7.55 (m, 4H), 7.44−7.32 (m, 6H), 4.78 (d, J = 3.4 Hz, 1H), 1.95−1.89 (m, 2H), 1.61−1.48 (m, 7H); 13 C{1H} NMR (101 MHz, CDCl3) δ 135.6, 134.8, 129.5, 128.0, 29.3, 27.0, 22.7; IR (KBr) vmax 2947, 1427, 1108, 799, 695 cm−1; HRMS (ESI) calcd for C17H20NaSi m/z 275.1226 [M + Na]+, found 275.1224. Cyclohexyldiphenylsilane (20).24 Colorless oil, 25 mg, 31% yield; 1 H NMR (400 MHz, CDCl3) δ 7.62−7.54 (m, 4H), 7.43−7.33 (m, 6H), 4.68 (d, J = 2.8 Hz, 1H), 1.83−1.78 (m, 2H), 1.75−1.67 (m, 3H), 1.34−1.23 (m, 6H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.7, 134.0, 129.6, 128.0, 28.5, 28.0, 26.9, 23.5; IR (KBr) vmax 2918, 1427, 1112, 798, 695 cm−1; HRMS (ESI) calcd for C18H23Si m/z 267.1564 [M + H]+, found 267.1567. Cycloheptyldiphenylsilane (21). Colorless oil, 52 mg, 62% yield; 1H NMR (400 MHz, CDCl3) δ 7.65−7.52 (m, 4H), 7.47−7.31 (m, 6H), 4.75 (s, 1H), 1.96−1.87 (m, 2H), 1.82−1.70 (m, 2H), 1.69−1.56 (m, 2H), 1.55−1.37 (m, 7H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.7, 134.4, 129.5, 128.0, 30.0, 29.9, 28.4, 23.7; IR (KBr) vmax 2981, 1427, 1107, 797, 727, 696 cm−1; HRMS (ESI) calcd for C19H25Si m/z 281.1720 [M + H]+, found 281.1718. Cyclooctyldiphenylsilane (22). Colorless oil, 71 mg, 91% yield; 1H NMR (400 MHz, CDCl3) δ 7.65−7.54 (m, 4H), 7.45−7.33 (m, 6H), 4.74 (d, J = 1.8 Hz, 1H), 1.93−1.83 (m, 2H), 1.73−1.47 (m, 13H); 13 C{1H} NMR (101 MHz, CDCl3) δ 135.7, 134.5, 129.5, 128.0, 28.6, 27.7, 27.3, 26.4, 21.0; IR (KBr) vmax 2916, 2109, 1427, 1107, 798, 727, 696 cm−1; HRMS (ESI) calcd for C20H27Si m/z 295.1877 [M + H]+, found 295.1866. [(1S,2S,4R)-Bicyclo[2.2.1]heptan-2-yl]diphenylsilane (23).25 Colorless oil, 68 mg, 81% yield; 1H NMR (400 MHz, CDCl3) δ 7.68−7.50 (m, 4H), 7.49−7.27 (m, 6H), 4.74 (d, J = 5.3 Hz, 1H), 2.42−2.18 (m, 2H), 1.66−1.55 (m, 4H), 1.40−1.27 (m, 4H), 1.20−1.13 (m, 1H); 13 C{1H} NMR (101 MHz, CDCl3) δ 135.6, 135.5, 135.2, 134.4, 129.5, 128.0, 128.0, 38.6, 37.6, 37.4, 34.0, 33.7, 29.3, 25.8; IR (KBr) vmax 2946, 2110, 1727, 1111, 791, 727, 695 cm−1; HRMS (ESI) calcd for C19H23Si m/z 279.1564 [M + H]+, found 279.1574. Diphenyl(tetrahydrofuran-3-yl)silane (24). Colorless oil, 24 mg, 31% yield; 1H NMR (400 MHz, CDCl3) δ 7.63−7.51 (m, 4H), 7.49− 7.34 (m, 6H), 4.87 (d, J = 3.8 Hz, 1H), 4.14 (t, J = 8.4 Hz, 1H), 3.81 (td, J1 = 8.1 Hz, J2 = 3.4 Hz, 1H), 3.72 (td, J1 = 8.1 Hz, J2 = 6.6 Hz, 1H), 3.65 (dd, J1 = 10.7 Hz, J2 = 8.4 Hz, 1H), 2.20−2.12 (m, 1H), 2.06−1.92 (m, 1H), 1.90−1.79 (m, 1H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.4, 135.4, 133.2, 130.1, 130.0, 128.3, 70.9, 68.5, 29.6, 24.0; IR (KBr) vmax G

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

Article

The Journal of Organic Chemistry 2924, 1427, 1109, 798, 727, 695 cm−1; HRMS (ESI) calcd for C16H18NaOSi m/z 277.1119 [M + Na]+, found 277.1120. cis-(4S,5S)-4-(Diphenylsilyl)-5-methyldihydrofuran-2(3H)-one (cis-25). Colorless oil, 24 mg, 28% yield; 1H NMR (400 MHz, CDCl3) δ 7.60−7.54 (m, 4H), 7.49−7.39 (m, 6H), 4.93 (d, J = 2.9 Hz, 1H), 4.62−4.52 (m, 1H), 2.70 (dd, J1 = 17.6 Hz, J2 = 8.9 Hz, 1H), 2.52 (dd, J1 = 17.6 Hz, J2 = 13.0 Hz, 1H), 2.10−1.97 (m, 1H), 1.32 (d, J = 6.1 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 176.9, 135.5, 135.4, 130.7, 128.6, 80.3, 33.1, 29.5, 21.2; IR (KBr) vmax 2922, 2126, 1774, 1050, 792, 730, 698 cm−1; HRMS (ESI) calcd for C17H18NaO2Si m/z 305.0968 [M + Na]+, found 305.0967. trans-(4R,5S)-4-(Diphenylsilyl)-5-methyldihydrofuran-2(3H)-one (trans-25). Colorless oil, 18 mg, 22% yield; 1H NMR (400 MHz, CDCl3) δ 7.64−7.52 (m, 4H), 7.50−7.36 (m, 6H), 4.98 (d, J = 4.6 Hz, 1H), 4.96−4.90 (m, 1H), 2.66−2.59 (m, 2H), 2.58−2.51 (m, 1H), 1.32 (d, J = 6.6 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 177.1, 135.1, 135.1, 132.0, 131.7, 130.6, 130.5, 128.7, 128.5, 79.5, 30.5, 26.12 19.2; IR (KBr) vmax 2929, 2131, 1776, 1060, 743, 688 cm−1; HRMS (ESI) calcd for C17H18NaO2Si m/z 305.0968 [M + Na]+, found 305.0966. Hexan-3-yldiphenylsilane (26). Colorless oil, 41 mg, 51% yield; 1H NMR (400 MHz, CDCl3) δ 7.72−7.51 (m, 4H), 7.49−7.31 (m, 6H), 4.88 (d, J = 2.4 Hz, 1H), 1.71−1.58 (m, 1H), 1.57−1.40 (m, 4H), 1.39−1.27 (m, 2H), 0.96 (t, J = 7.4 Hz, 3H), 0.87 (t, J = 7.1 Hz, 3H); 13 C{1H} NMR (101 MHz, CDCl3) δ 135.7, 134.5, 129.5, 128.0, 32.0, 24.9, 22.9, 22.0, 14.4, 13.6; IR (KBr) vmax 2956, 2116, 1259, 1014, 795, 696 cm−1; HRMS (ESI) calcd for C18H25Si m/z 269.1720 [M + H]+, found 269.1714. (3S)-6-(Diphenylsilyl)-3,7-dimethyloctan-1-ol (27). Colorless oil containing two diastereomers in a 1/1 ratio, 60 mg, 59% yield; 1H NMR (400 MHz, CDCl3) δ 7.66−7.55 (m, 8H), 7.48−7.29 (m, 12H), 4.91 (d, J = 3.3 Hz, 2H), 3.52 (t, J = 6.6 Hz, 4H), 2.03−2.00 (m, 2H), 1.59− 1.45 (m, 4H), 1.45−1.42 (m, 1H), 1.42−1.38 (m, 2H), 1.36 (d, J = 3.2 Hz, 1H), 1.35−1.31 (m, 1H), 1.29 (d, J = 5.3 Hz, 1H), 1.28−1.24 (m, 3H), 1.24−1.17 (m, 2H), 1.16−1.10 (m, 2H), 1.08−1.00 (m, 1H), 0.97 (d, J = 6.6 Hz, 6H), 0.96−0.93 (m, 6H), 0.77−0.74 (m, 6H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.8, 135.5, 135.1, 129.4, 128.0, 128.0, 61.2, 39.9, 39.8, 37.6, 31.6, 31.6, 29.9, 29.8, 29.3, 29.2, 25.1, 25.0, 22.4, 22.3, 21.7, 21.6, 19.6, 19.6; IR (KBr) vmax 2923, 2118, 1428, 1259, 1012, 792, 698 cm−1; HRMS (ESI) calcd for C22H32NaOSi m/z 363.2115 [M + Na]+, found 363.2110. {2-[(S)-4-Methylcyclohex-3-en-1-yl]propyl}diphenylsilane (29). Colorless oil containing two diastereomers in a 1/1 ratio, 56 mg, 58% yield; 1H NMR (400 MHz, chloroform-d) δ 7.64−7.55 (m, 8H), 7.46− 7.33 (m, 12H), 5.40 (s, 2H), 5.02−4.93 (m, 2H), 2.07−1.92 (m, 6H), 1.85−1.68 (m, 6H), 1.66 (s, 6H), 1.52−1.37 (m, 4H), 1.33−1.22 (m, 2H), 1.10−1.00 (m, 2H), 0.96 (d, J = 6.7 Hz, 6H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.2, 135.1, 135.0, 134.0, 129.5, 129.4, 128.0, 128.0, 121.0, 120.9, 108.1, 40.9, 40.9, 34.0, 33.8, 30.9, 30.9, 28.8, 27.9, 26.7, 25.5, 23.5, 19.1, 18.8, 17.6, 17.1; IR (KBr) vmax 2921, 2119, 1428, 1115, 801, 696 cm−1; HRMS (ESI) calcd for C22H29Si m/z 321.2033 [M + H]+, found 321.2040. (4R,4aS,6R)-6-[1-(Diphenylsilyl)propan-2-yl]-4,4a-dimethyl4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one (30). Colorless oil containing two diastereomers in a 1/1 ratio, 51 mg, 42% yield; 1H NMR (400 MHz, CDCl3) δ 7.61−7.51 (m, 8H), 7.44−7.26 (m, 12H), 5.76−5.68 (m, 2H), 5.02−4.88 (m, 2H), 2.44−2.33 (m, 1H), 2.31 (td, J = 5.2, 4.3, 2.6 Hz, 1H), 2.29−2.26 (m, 2H), 2.25 (d, J = 4.1 Hz, 1H), 2.23−2.20 (m, 2H), 2.17 (dt, J = 5.5, 4.1 Hz, 1H), 2.03−1.87 (m, 3H), 1.82 (dt, J = 12.9, 2.8 Hz, 1H), 1.78 (q, J = 2.7 Hz, 2H), 1.77−1.72 (m, 1H), 1.69−1.59 (m, 4H), 1.33−1.25 (m, 2H), 1.21−1.14 (m, 1H), 1.14−1.08 (m, 2H), 1.07−1.01 (m, 2H), 0.99 (s, 3H), 0.97 (s, 3H), 0.95−0.93 (m, 6H), 0.92−0.90 (m, 6H); 13C{1H} NMR (101 MHz, CDCl3) δ 199.9, 171.6, 135.2, 135.1, 134.7, 134.5, 129.7, 129.6, 128.1, 128.1, 124.5, 42.8, 42.2, 42.1, 41.1, 40.7, 40.6, 39.6, 39.4, 39.4, 39.3, 34.3, 34.2, 33.2, 33.1, 29.9, 28.3, 19.1, 18.8, 18.0, 17.4, 17.0, 15.1, 15.0; IR (KBr) vmax 2924, 2117, 1667, 1108, 801, 698 cm−1; HRMS (ESI) calcd for C27H34NaOSi m/z 425.2271 [M + Na]+, found 425.2269. [2-(Cyclohex-3-en-1-yl)ethyl]diphenylsilane (31).23 Colorless oil, 38 mg, 44% yield; 1H NMR (400 MHz, CDCl3) δ 7.68−7.53 (m, 4H), 7.48−7.32 (m, 6H), 5.67 (d, J = 2.4 Hz, 2H), 4.88 (t, J = 3.5 Hz, 1H),

2.21−2.10 (m, 1H), 2.09−1.99 (m, 2H), 1.78 (m, 1H), 1.73−1.64 (m, 1H), 1.63−1.56 (m, 1H), 1.49−1.42 (m, 2H), 1.25−1.14 (m, 3H); 13 C{1H} NMR (101 MHz, CDCl3) δ 135.1, 134.6, 129.5, 128.0, 127.1, 126.6, 36.4, 31.6, 31.1, 28.5, 25.3, 9.3; IR (KBr) vmax 2927, 1720, 1260, 1097, 800 cm−1; HRMS (ESI) calcd for C20H25Si m/z 293.1720 [M + H]+, found 293.1722. (E)-[4-(Hex-3-en-1-yloxy)butyl]triphenylsilane (32). Colorless oil, 77 mg, 62% yield; 1H NMR (400 MHz, CDCl3) δ 7.60−7.54 (m, 6H), 7.45−7.35 (m, 9H), 5.63−5.53 (m, 1H), 5.49−5.39 (m, 1H), 3.47− 3.39 (m, 4H), 2.35−2.25 (m, 2H), 2.11−1.99 (m, 2H), 1.61−1.52 (m, 4H), 1.47−1.35 (m, 6H), 1.01 (t, J = 7.5 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.7, 134.1, 129.4, 127.9, 125.3, 71.0, 70.8, 33.7, 33.1, 29.7, 25.8, 25.7, 24.0, 13.9, 13.3; IR (KBr) vmax 2924, 1259, 1108, 796, 697 cm−1; HRMS (ESI) calcd for C28H35OSi m/z 415.2452 [M + H]+, found 415.2458. [4-(Hex-5-en-1-yloxy)-2-methylbutyl]triphenylsilane (33) and {6[(3-Methylbut-3-en-1-yl)oxy]hexyl}triphenylsilane (34). Colorless oil containing 33 and 34 in a 1.87/1 ratio, 55 mg, 43% yield; 1H NMR (500 MHz, CDCl3) δ 7.68−7.55 (m, 8.8H), 7.52−7.36 (m, 13.0H), 5.93− 5.79 (m, 0.9H), 5.13−4.96 (m, 1.8H), 4.88−4.77 (m, 1H), 3.62−3.53 (m, 1.0H), 3.51−3.30 (m, 4.9H), 2.42−2.31 (m, 1.0H), 2.17−2.07 (m, 1.9H), 2.07−1.96 (m, 1.0H), 1.84−1.79 (m, 1.4H), 1.74−1.64 (m, 1.9H), 1.64−1.52 (m, 5.2H), 1.51−1.33 (m, 6.3H), 1.00−0.83 (m, 2.9H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.8, 135.7, 129.4, 127.9, 114.6, 111.4, 71.1, 70.7, 69.4, 69.1, 40.4, 37.9, 33.7, 29.8, 29.4, 26.6, 25.8, 25.6, 24.0, 23.4, 22.9, 21.7, 13.4; IR (KBr) vmax 2923, 1427, 1259, 1108, 1016, 796, 698 cm−1; HRMS (ESI) calcd for C29H36NaOSi m/z 451.2428 [M + Na]+, found 451.2430. (2-Methyl-4-{[6-(triphenylsilyl)hexyl]oxy}butyl)triphenylsilane (35). Colorless oil, 41 mg, 20% yield; 1H NMR (400 MHz, CDCl3) δ 7.62−7.49 (m, 12H), 7.47−7.29 (m, 18H), 3.40−3.31 (m, 2H), 3.27 (t, J = 6.6 Hz, 2H), 2.00−1.90 (m, 1H), 1.67−1.58 (m, 2H), 1.57−1.44 (m, 6H), 1.42−1.35 (m, 4H), 1.33−1.27 (m, 2H), 0.85 (d, J = 6.6 Hz, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 135.8, 135.8, 135.5, 129.5, 129.4, 128.0, 127.9, 71.0, 69.1, 40.4, 33.8, 29.9, 26.7, 25.9, 24.0, 23.4, 21.7, 13.4; IR (KBr) vmax 2923, 1720, 1259, 1106, 726, 696 cm−1; HRMS (ESI) calcd for C47H52NaOSi2 m/z 711.3449 [M + Na]+, found 711.3434. Triphenyl(4-phenylbutyl)silane (36). Colorless oil, 105 mg, 89% yield; 1H NMR (400 MHz, CDCl3) δ 7.64−7.53 (m, 6H), 7.51−7.37 (m, 9H), 7.35−7.27 (m, 2H), 7.25−7.16 (m, 3H), 2.70−2.60 (m, 2H), 1.80−1.71 (m, 2H), 1.68−1.59 (m, 2H), 1.51−1.45 (m, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ 142.7, 135.7, 135.3, 129.4, 128.4, 128.2, 127.9, 125.6, 35.5, 35.4, 23.7, 13.1; IR (KBr) vmax 2924, 1427, 1263, 1108, 1016, 733, 699 cm−1; HRMS (ESI) calcd for C28H28NaSi m/z 415.1852 [M + Na]+, found 415.1861. (3S,5S,6R,8S,9S,10R,13S,14S,17S)-17-Acetyl-6-(diphenylsilyl)10,13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthren-3-yl Acetate (37). Colorless oil, 107 mg, 66% yield; 1H NMR (400 MHz, CDCl3) δ 7.64−7.54 (m, 4H), 7.33 (dd, J1 = 7.1 Hz, J2 = 5.7 Hz, 6H), 5.07 (d, J = 2.0 Hz, 1H), 4.67 (dt, J1 = 10.2 Hz, J2 = 6.2 Hz, 1H), 2.44 (t, J = 8.9 Hz, 1H), 2.06 (s, 3H), 1.98 (s, 3H), 1.96−1.88 (m, 2H), 1.82− 1.75 (m, 2H), 1.74−1.72 (m, 1H), 1.71−1.68 (m, 1H), 1.66−1.57 (m, 2H), 1.57−1.48 (m, 3H), 1.47−1.40 (m, 1H), 1.39−1.09 (m, 4H), 1.09−0.97 (m, 3H), 0.95 (s, 3H), 0.87 (dt, J1 = 11.8 Hz, J2 = 5.9 Hz, 1H), 0.72−0.61 (m, 1H), 0.30 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ 209.7, 170.8, 136.1, 136.0, 135.3, 134.9, 129.6, 129.4, 128.0, 127.9, 73.9, 63.8, 56.2, 54.5, 47.6, 39.0, 38.0, 34.7, 34.3, 33.3, 31.6, 27.6, 26.5, 24.1, 22.7, 21.5, 21.2, 15.7, 13.2; IR (KBr) vmax 2923, 2134, 1729, 1244, 1024, 797, 732, 700 cm−1; HRMS (ESI) calcd for C35H46NaO3Si m/z 565.3108 [M + Na]+, found 565.3104. (3S,5S,6R,8S,9S,10R,13R,14S,17R)-6-(Diphenylsilyl)-17-[(2R,5S,E)5-ethyl-6-methylhept-3-en-2-yl]-10,13-dimethylhexadecahydro1H-cyclopenta[a]phenanthren-3-ol (38). White solid, 65 mg, 36% yield; mp 143−144 °C; 1H NMR (400 MHz, CDCl3) δ 7.66−7.58 (m, 4H), 7.37−7.30 (m, 6H), 5.16−5.08 (m, 2H), 5.00 (dd, J1 = 15.2 Hz, J2 = 8.6 Hz, 1H), 3.62−3.46 (m, 1H), 2.03−1.94 (m, 1H), 1.93−1.85 (m, 2H), 1.82−1.58 (m, 6H), 1.58−1.42 (m, 6H), 1.41−1.26 (m, 4H), 1.24−1.12 (m, 5H), 1.12−1.06 (m, 2H), 1.01−0.94 (m, 7H), 0.87− 0.79 (m, 9H), 0.67−0.55 (m, 1H), 0.46 (s, 3H); 13C{1H} NMR (101 H

DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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The Journal of Organic Chemistry MHz, CDCl3) δ 138.5, 136.6, 135.9, 135.4, 135.3, 129.4, 129.3, 128.0, 127.9, 71.9, 56.2, 56.1, 54.9, 51.4, 48.0, 42.5, 40.6, 40.0, 39.2, 38.4, 36.7, 34.5, 33.5, 32.0, 31.7, 29.0, 27.0, 25.5, 24.1, 21.3, 21.2, 19.1, 15.9, 12.4, 12.1; IR (KBr) vmax 2927, 1720, 1260, 1097, 800, 729, 699 cm−1; HRMS (ESI) calcd for C41H60NaOSi m/z 619.4306 [M + Na]+, found 619.4297.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.8b02409. Copies of 1H and 13C NMR spectra (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Shaozhong Wang: 0000-0002-7766-4433 Zhu-Jun Yao: 0000-0002-6716-4232 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The work was financially supported by the National Science Foundation of China (21572098, 21871132, 21778031, and 21532002), the National Key Research and Development Program of China (2018YFC0310900), and Fundamental Research Funds for the Central Universities (020514380131).

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REFERENCES

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DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.joc.8b02409 J. Org. Chem. XXXX, XXX, XXX−XXX