amines Containing the Silicon Protecting Groups MOP (4

Article pubs.acs.org/Organometallics

Synthesis of 4‑Silacyclohexan-1-ones and (4-Silacyclohexan-1yl)amines Containing the Silicon Protecting Groups MOP (4Methoxyphenyl), DMOP (2,4-Dimethoxyphenyl), or TMOP (2,4,6Trimethoxyphenyl): Versatile Si- and C‑Functional Building Blocks for Synthesis Markus Fischer, Christian Burschka, and Reinhold Tacke* Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany S Supporting Information *

ABSTRACT: The 4-silacyclohexanones 1−6 were prepared in convenient multistep syntheses, starting from MeSi(OMe)3 and PhSi(OMe)3, respectively. Cleavage of the 4-methoxyphenyl (MOP), 2,6-dimethoxyphenyl (DMOP), and 2,4,6-trimethoxyphenyl (TMOP) protecting groups of 4−6 by treatment with HCl/Et2O in CH2Cl2 at 20 °C gives the 4-chloro-4-silacyclohexanone 13. Reductive amination of 1−6 with NH3 or i-PrNH2 yields the respective (4silacyclohexan-1-yl)amines 7−12. Compounds 1−12 and all new precursors synthesized were characterized by elemental analyses (C, H, N) or mass spectrometric investigations (ESI-HRMS) and by NMR spectroscopic studies (1H, 13C, 29Si). Compounds 1, 3, 5, and 6 and the precursors (MeO)2SiPh(TMOP) (21) and (CH2CH)2SiPh(TMOP) (27) were additionally characterized by single-crystal X-ray diffraction. Compounds 1−12 with their Si- and C-functional groups represent versatile building blocks for synthesis.

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INTRODUCTION

Cyclohexanones and cyclohexylamines are important building blocks in the synthesis of drugs. As part of our ongoing studies on silicon-based drugs,1,2 we have been interested in the development of versatile silicon-containing building blocks for synthesis, such as 4-((2-halogeno-5-pyridyl)dimethylsilyl)phenylboronic acids,3 (2-halogeno-5-pyridyl)dimethyl(oxiran2-ylmethyl)silanes,4 4-silapiperidines,5 and other classes of organosilicon compounds. In continuation of these studies, we have now succeeded in synthesizing a series of new 4silacyclohexanones and (4-silacyclohexan-1-yl)amines that contain the silicon protecting groups MOP (4-methyoxyphenyl), DMOP (2,4-dimethoxyphenyl), or TMOP (2,4,6-trimethoxyphenyl). In previous studies, we have demonstrated that these protecting groups can be easily removed from the silicon atom via protodesilylation under mild conditions.6 Therefore, the Si−MOP, Si−DMOP, and Si−TMOP moieties can also be regarded as Si-functional groups. As a proof of principle, we also report here on the cleavage of the MOP, DMOP, and TMOP groups of 4−6 to give the 4-chloro-4-silacyclohexanone 13. With the transformations of 4−6 into 7−12 via a reductive amination, we have also made use of the second functional group (keto group) of the 4-silacyclohexanones described herein. © 2014 American Chemical Society

Received: December 19, 2013 Published: February 11, 2014 1020

dx.doi.org/10.1021/om401208y | Organometallics 2014, 33, 1020−1029

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RESULTS AND DISCUSSION Syntheses. The 4-silacyclohexanones 1−6 were synthesized according to Scheme 1, starting from trimethoxymethylsilane

Scheme 2. Syntheses of Compounds 7−13

Scheme 1. Syntheses of Compounds 1−6

for these transformations (for details, see the Experimental Section). In all cases, quantitative and selective cleavage reactions were achieved to give the respective mixtures 13/HMOP, 13/H-DMOP, and 13/H-TMOP. The 1H, 13C, and 29Si NMR spectra and GC/MS spectra of these mixtures are depicted in the Supporting Information (Figures S1−S15). In contrast to our earlier studies, where the cleavage of the MOP, DMOP, and TMOP protecting groups was performed in diethyl ether, in this study dichloromethane was used as the dominating solvent (see the Experimental Section). It is interesting to note that the usage of dichloromethane speeds up the cleavage reaction significantly. The identities of the new compounds 1−12, 17−21, and 23−27 were established by NMR spectroscopic studies (1H, 13 C, 29Si) and elemental analyses (C, H, N) or mass spectrometric investigations (ESI-HRMS). The 1:1 mixtures of 13/H-MOP, 13/H-DMOP, and 13/H-TMOP were characterized by NMR spectroscopic studies (1H, 13C, 29Si) and GC/MS investigations (see the Supporting Information). In addition, compounds 1, 3, 5, 6, 21, and 27 were studied by crystal structure analyses. Crystal Structure Analyses. Compounds 1, 3, 5, 6, 21, and 27 were structurally characterized by single-crystal X-ray diffraction. The crystal data and the experimental parameters used for the crystal structure analyses are given in the Supporting Information (Table S1). The molecular structures of 1, 3, 5, 6, 21, and 27 are depicted in Figures 1−6. All the bond lengths and angles of these compounds are in the expected ranges and do not need any further discussion; however, the structural features of the 4-silacyclohexanones 1, 3, 5, and 6 deserve a brief discussion.9 Except for one of the two crystallographically independent molecules of 5 (twist conformation), all the compounds studied adopt a chair conformation in the crystal. In the case of 3, 5, and 6, the bulky 2,6-dimethoxyphenyl and 2,4,6-trimethoxyphenyl group, respectively, occupy an equatorial position. In contrast, the less bulky 4-methoxyphenyl group of 1 is found in an axial site. NMR Studies. The 1H, 13C, and 29Si NMR spectroscopic studies confirmed the identities of the new silicon compounds synthesized. Moreover, they revealed some insight into the stereochemistry of the 4-silacyclohexane derivatives studied.

(14) and trimethoxyphenylsilane (15), respectively. Thus, treatment of 14 and 15 with (4-methoxyphenyl)magnesium bromide, (2,6-dimethoxyphenyl)lithium, or (2,4,6-trimethoxyphenyl)lithium afforded the corresponding dimethoxydiorganylsilanes 16−21, which upon reaction with vinylmagnesium chloride furnished the respective divinyldiorganylsilanes 22− 27. In the last step, compounds 22−27 were transformed into the corresponding 4-silacyclohexanones 1−6 by using a synthetic method developed by Brown, Soderquist, et al.8 Compounds 1−6 were isolated as colorless crystalline solids (yields: 1, 74%; 2, 73%; 3, 82%; 4, 79%; 5, 80%; 6, 81%), whereas 16−27 were obtained as colorless liquids (yields: 16, 71%; 17, 71%; 18, 77%; 19, 70%; 20, 68%; 21, 67%; 22, 70%; 23, 72%; 24, 75%; 25, 90%; 26, 76%; 27, 70%). The (4-silacyclohexan-1-yl)amines 7−12 were synthesized by reductive amination according to Scheme 2, starting from the respective 4-silacyclohexanones 4−6.8 Thus, treatment of 4−6 with ammonia or isopropylamine in an autoclave under an atmosphere of hydrogen, in the presence of Raney nickel, afforded the corresponding amines 7−12, which were isolated as colorless liquids (yields: 7, 73%; 8, 61%; 9, 79%; 10, 77%; 11, 74%; 12, 81%). As a proof of principle, the MOP, DMOP, and TMOP protecting groups of the 4-silacyclohexanones 4−6 were removed by treatment with hydrogen chloride/diethyl ether in dichloromethane at 20 °C to give the corresponding 4chloro-4-silacyclohexanone 13 (Scheme 2). According to the different reactivities of the Si−MOP, Si−DMOP, and Si− TMOP moieties,6c different reaction conditions were applied 1021


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Figure 1. Molecular structure of 1 in the crystal (probability level of displacement ellipsoids 50%).

Figure 3. Molecular structures of the two crystallographically independent molecules in the crystal of 5 (probability level of displacement ellipsoids 50%).


The results of the crystal structure analyses of compounds 1, 3, 5, and 6 suggest that the 4-silacyclohexanones 1−6 and 13 also adopt a chair conformation in solution. As shown in Scheme 3, two conformers of this type have to be considered, and it is likely to assume that the conformer with the most bulky substituent in equatorial position is the dominating species. For compounds 1−6 and 13, only one set of resonance signals was observed in the 1H, 13C, and 29Si NMR spectra, indicating a rapid chair-to-chair inversion on the NMR time scale. A totally different stereochemistry was observed for the (4silacyclohexan-1-yl)amines 7−12. In the case of compounds 7 and 8, two sets of resonance signals each were observed in the 1 H, 13C, and 29Si NMR spectra, with intensity ratios of 1:1.1 and 1:1.6, respectively. These two sets of resonance signals can be assigned to the two diastereomers shown in Scheme 4. As the steric demand of the phenyl and 4-methoxyphenyl group is very similar, an NMR spectroscopic differentiation between the two chair conformations of the diastereomers of 7 and 8 is not possible under the experimental conditions applied. However, in the case of compounds 9−12, four sets of resonance signals were observed in the NMR spectra, indicating the presence of two diastereomers each, the two conformers of which are stable on the NMR time scale. The population ratios of these four species are as follows: 9, 1:2.1:7.5:9.4; 10, 1:1.1:2.2:3.5; 11, 1:1.3:23:28; 12, 1:1.7:3.2:5.1. These ratios reflect the different steric demand of the unsubstituted and substituted phenyl groups and of the unsubstituted and substituted amino groups.


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CONCLUSION With the synthesis of compounds 1−6, a new class of 4silacyclohexanones with a Si−MOP, Si−DMOP, or Si−TMOP moiety was made available. These compounds were prepared by a convenient multistep synthesis, starting from trimethoxymethylsilane and trimethoxyphenylsilane, respectively. The MOP, DMOP, and TMOP protecting groups can be easily removed via protodesilylation under mild conditions. As a proof of principle, compounds 4−6 were converted quantitatively and selectively into the corresponding 4-chloro-4silacyclohexanone 13 by treatment with hydrogen chloride/ diethyl ether at 20 °C. With the transformations of the 4silacyclohexanones 1−6 into the corresponding (4-silacyclohex1022


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an-1-yl)amines 7−12 via a reductive amination, the keto group of 1−6 was also demonstrated to be a useful functional group for further conversions. In conclusion, both the 4-silacyclohexanones 1−6 and the (4-silacyclohexan-1-yl)amines 7−12 with their Si- and C-functional groups represent versatile building blocks for synthesis.

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EXPERIMENTAL SECTION

General Procedures. All syntheses in organic solvents were carried out under dry argon. The organic solvents used were dried and purified according to standard procedures and stored under dry argon. Starting materials and reagents were purchased from ABCR, Acros, or Aldrich and were used without further purification. Bulb-to-bulb distillations were accomplished by using a Büchi GKR-50 glass oven apparatus. Melting points were determined with a Büchi B-540 melting point apparatus using samples in open glass capillaries. The 1H, 13C, and 29Si NMR spectra were recorded at 23 °C on a Bruker Avance 500 NMR spectrometer (1H, 500.1 MHz; 13C, 125.8 MHz; 29Si, 99.4 MHz) using CDCl3 or CD2Cl2 as the solvent. Chemical shifts (ppm) were determined relative to internal CHCl3 (1H, δ 7.24 ppm; CDCl3), CHDCl2 (1H, δ 5.32 ppm; CD2Cl2), CDCl3 (13C, δ 77.0 ppm; CDCl3), CD2Cl2 (13C, δ 53.8 ppm; CD2Cl2), or external TMS (29Si, δ 0 ppm; CDCl3, CD2Cl2). Analysis and assignment of the 1H and 13C NMR spectroscopic data was supported by 1H,1H gradient selected COSY along with 13C,1H gradient selected HMQC and HMBC experiments. Assignment of the 13C NMR spectroscopic data was additionally supported by DEPT 135 experiments. Coupling constants are given as their absolute values. GC/MS studies were performed using a Varian 450-GC gas chromatograph with a capillary column from Varian of the type FactorFour VF-5 ms (column length, 30 m; column inside diameter, 0.25 mm; flow rate, 1.0 mL min−1; injector, split ratio 1:80, 220 °C; carrier gas, He) and a Varian 320-MS SQ mass spectrometer (70 eV). HRMS spectra were recorded on a Bruker MicrOTOF mass spectrometer using solutions in methanol (ESI). Elemental analyses were performed by using a VarioMicro apparatus (Elementar Analysensysteme GmbH) or a EURO EA elemental analyzer (EuroVector). 4-(4-Methoxyphenyl)-4-methyl-4-silacyclohexan-1-one (1). 9Borabicyclo[3.3.1]nonane (11.7 g, 47.9 mmol of the 9-BBN dimer) was added in a single portion at 20 °C to a stirred solution of 22 (8.89 g, 43.5 mmol) in n-hexane (120 mL), and the resulting mixture was heated under reflux for 2 h. The reaction mixture was then cooled to 20 °C, borane dimethyl sulfide complex (3.64 g, 47.9 mmol) was added in a single portion, and the resulting mixture was heated under reflux for 2 h. Subsequently, the mixture was cooled to 0 °C, methanol (8 mL) was added dropwise within 30 min, and the resulting solution was then stirred at 20 °C for 1 h. The volatile components were removed under reduced pressure at 30 °C, and the oily residue was dissolved in tetrahydrofuran (120 mL), followed by the addition of dichloromethyl methyl ether (7.50 g, 65.2 mmol) in a single portion at 0 °C. Subsequently, a solution of lithium tert-butoxide (prepared from tert-butanol (16.1 g, 217 mmol) in tetrahydrofuran (85 mL) and a 2.5 M solution of n-butyllithium in hexanes (96 mL; 240 mmol of nBuLi)) was added dropwise at 0 °C within 45 min, and the reaction mixture was stirred at 0 °C for 10 min and then at 20 °C for a further 45 min. The reaction mixture was then treated with ethanol (33 mL), water (35 mL), and sodium hydroxide (5.28 g, 132 mmol), the resulting mixture was cooled to 0 °C, and an aqueous solution of hydrogen peroxide (30 weight %, 40 mL) was added dropwise within 30 min. The mixture was warmed to 20 °C within 30 min, stirred at this temperature for 16 h, and then heated under reflux for 1 h. Subsequently, water (75 mL) and diethyl ether (60 mL) were added at 20 °C, the organic layer was separated, and the aqueous layer was extracted with diethyl ether (3 × 60 mL) and discarded. The combined organic phases were dried over anhydrous sodium sulfate, the organic solvents were removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation (147−149 °C/0.2 mbar). The resulting solid distillate was recrystallized from diethyl ether (slow cooling of a saturated boiling solution to −20 °C), and the



Scheme 3. Chair-to-Chair Inversion of Compounds 1−6 and 13 in Solution

Scheme 4. Structures of the Two Chair Conformations of the Two Diastereomers of Compounds 7−12 in Solution

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product was isolated by filtration and dried in vacuo (0.005 mbar, 20 °C, 4 h) to give 1 in 74% yield as a colorless crystalline solid (7.58 g, 32.3 mmol); mp 35 °C. 1H NMR (CD2Cl2): δ 0.38 (s, 3 H; SiCH3), 1.06−1.15 and 1.20−1.30 (m, 4 H; SiCH2CH2C), 2.49−2.59 (m, 4 H; SiCH2CH2C), 3.81 (s, 3 H; C6H4OCH3), 6.92−6.96 (m, 2 H; H-3/H5, C6H4OCH3), 7.48−7.52 ppm (m, 2 H; H-2/H-6, C6H4OCH3). 13C NMR (CD2Cl2): δ −3.8 (SiCH3), 10.1 (SiCH2CH2C), 38.2 (SiCH2CH2C), 55.4 (C6H4OCH3), 114.1 (C-3/C-5, C6H4OCH3), 127.7 (C-1, C6H4OCH3), 135.5 (C-2/C-6, C6H4OCH3), 161.3 (C-4, C6H4OCH3), 214.2 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ −7.8 ppm. Anal. Calcd for C13H18O2Si: C, 66.62; H, 7.74. Found: C, 66.42; H, 7.93. 4-(2,6-Dimethoxyphenyl)-4-methyl-4-silacyclohexan-1-one (2). Compound 2 was synthesized by using the same procedure as described for the preparation of 1, starting from 23 (10.2 g, 43.5 mmol). The product was purified by bulb-to-bulb distillation (159− 160 °C/0.2 mbar), and the resulting solid distillate was recrystallized from n-hexane/ethyl acetate (1:1 v/v; slow cooling of a saturated boiling solution to −20 °C). The product was isolated by filtration and dried in vacuo (0.005 mbar, 20 °C, 4 h) to give 2 in 73% yield as a colorless crystalline solid (8.39 g, 31.7 mmol); mp 49 °C. 1H NMR (CD2Cl2): δ 0.35 (s, 3 H; SiCH3), 1.08−1.18 and 1.37−1.48 (m, 4 H; SiCH2CH2C), 2.45−2.60 (m, 4 H; SiCH2CH2C), 3.76 (s, 6 H; C 6 H 3 (OCH 3 ) 2 , 6.53 (d, 3 J HH = 8.3 Hz, 2 H; H-3/H-5, C 6 H 3 (OCH 3 ) 2 ), 7.32 ppm (t, 3 J HH = 8.2 Hz, 1 H; H-4, C6H3(OCH3)2). 13C NMR (CD2Cl2): δ −2.4 (SiCH3), 12.1 (SiCH2CH2C), 38.6 (SiCH2CH2C), 55.5 (C6H3(OCH3)2), 103.8 (C3/C-5, C6H3(OCH3)2), 111.4 (C-1, C6H3(OCH3)2), 132.4 (C-4, C6H3(OCH3)2), 165.9 (C-2/C-6, C6H3(OCH3)2), 215.6 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ −9.2 ppm. Anal. Calcd for C14H20O3Si: C, 63.60; H, 7.62. Found: C, 63.43; H, 7.77. 4-Methyl-4-(2,4,6-trimethoxyphenyl)-4-silacyclohexan-1-one (3). Compound 3 was synthesized by using the same procedure as described for the preparation of 1, starting from 24 (20.0 g, 75.6 mmol). The product was purified by bulb-to-bulb distillation (243− 245 °C/0.1 mbar), and the resulting solid distillate was recrystallized from n-pentane/diethyl ether (1:1 v/v; slow cooling of a saturated boiling solution to −20 °C). The product was isolated by filtration and dried in vacuo (0.005 mbar, 20 °C, 5 h) to give 3 in 82% yield as a colorless crystalline solid (18.3 g, 62.2 mmol); mp 57 °C. 1H NMR (CD2Cl2): δ 0.32 (s, 3 H; SiCH3), 1.05−1.13 and 1.34−1.43 (m, 4 H; SiCH2CH2C), 2.44−2.57 (m, 4 H; SiCH2CH2C), 3.74 (s, 6 H; oOCH3, C6H2(OCH3)3), 3.81 (s, 3 H; p-OCH3, C6H2(OCH3)3), 6.09 ppm (s, 2 H; H-3/H-5, C6H2(OCH3)3). 13C NMR (CD2Cl2): δ −2.2 (SiCH3), 12.2 (SiCH2CH2C), 38.6 (SiCH2CH2C), 55.5 (o-OCH3, C6H2(OCH3)3), 55.6 (p-OCH3, C6H2(OCH3)3), 90.6 (C-3/C-5, C 6 H 2 (OCH 3 ) 3 ), 102.7 (C-1, C 6 H 2 (OCH 3 ) 3 ), 164.1 (C-4, C6H2(OCH3)3), 166.8 (C-2/C-6, C6H2(OCH3)3), 215.7 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ −9.8 ppm. Anal. Calcd for C15H22O4Si: C, 61.19; H, 7.53. Found: C, 61.23; H, 7.46. 4-(4-Methoxyphenyl)-4-phenyl-4-silacyclohexan-1-one (4). Compound 4 was synthesized by using the same procedure as described for the preparation of 1, starting from 25 (15.1 g, 56.7 mmol). The product was purified by bulb-to-bulb distillation (262−263 °C/1.6 mbar), and the resulting solid distillate was recrystallized from nhexane/ethyl acetate (1:1 v/v; slow cooling of a saturated boiling solution to −20 °C). The product was isolated by filtration and dried in vacuo (0.005 mbar, 20 °C, 4 h) to give 4 in 79% yield as a colorless crystalline solid (13.3 g, 44.9 mmol); mp 58 °C. 1H NMR (CD2Cl2): δ 1.45−1.54 (m, 4 H; SiCH2CH2C), 2.57−2.64 (m, 4 H; SiCH2CH2C), 3.81 (s, 3 H; C6H4OCH3), 6.93−6.98 (m, 2 H; H-3/H-5, C6H4OCH3), 7.35−7.43 (m, 2 H; H-3/H-5, C6H5), 7.38−7.45 (m, 1 H; H-4, C6H5), 7.48−7.53 (m, 2 H; H-2/H-6, C6H4OCH3), 7.55− 7.60 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 9.2 (SiCH2CH2C), 38.3 (SiCH2CH2C), 55.4 (C6H4OCH3), 114.3 (C-3/ C-5, C6H4OCH3), 125.4 (C-1, C6H4OCH3), 128.5 (C-3/C-5, C6H5), 130.1 (C-4, C6H5), 134.8 (C-2/C-6, C6H5), 135.5 (C-1, C6H5), 136.3 (C-2/C-6, C6H4OCH3), 161.5 (C-4, C6H4OCH3), 213.6 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ −12.6 ppm. Anal. Calcd for C18H20O2Si: C, 72.93; H, 6.80. Found: C, 72.53; H, 7.19.

4-(2,6-Dimethoxyphenyl)-4-phenyl-4-silacyclohexan-1-one (5). Compound 5 was synthesized by using the same procedure as described for the preparation of 1, starting from 26 (16.8 g, 56.7 mmol). The product was purified by bulb-to-bulb distillation (253− 254 °C/1.2 mbar), and the resulting solid distillate was recrystallized from n-hexane/ethyl acetate (1:1 v/v; slow cooling of a saturated boiling solution to −20 °C). The product was isolated by filtration and dried in vacuo (0.005 mbar, 20 °C, 5 h) to give 5 in 80% yield as a colorless crystalline solid (14.8 g, 45.3 mmol); mp 86 °C. 1H NMR (CD2Cl2): δ 1.53−1.72 (m, 4 H; SiCH2CH2C), 2.51−2.65 (m, 4 H; SiCH2CH2C), 3.73 (s, 6 H; C6H3(OCH3)2), 6.54 (d, 3JHH = 8.3 Hz, 2 H; H-3/H-5, C6H3(OCH3)2), 7.30−7.37 (m, 2 H; H-3/H-5, C6H5), 7.32−7.38 (m, 1 H; H-4, C6H5), 7.35 (t, 3JHH = 8.3 Hz, 1 H; H-4, C6H3(OCH3)2), 7.59−7.64 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD 2 Cl 2 ): δ 11.4 (SiCH 2 CH 2 C), 38.7 (SiCH 2 CH 2 C), 55.6 (C6H3(OCH3)2), 104.0 (C-3/C-5, C6H3(OCH3)2), 109.8 (C-1, C6H3(OCH3)2), 128.0 (C-3/C-5, C6H5), 129.3 (C-4, C6H5), 132.9 (C-4, C6H3(OCH3)2), 134.4 (C-2/C-6, C6H5), 137.6 (C-1, C6H5), 166.0 (C-2/C-6, C6H3(OCH3)2), 214.9 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ −14.4 ppm. Anal. Calcd for C19H22O3Si: C, 69.90; H, 6.79. Found: C, 69.78; H, 6.79. 4-Phenyl-4-(2,4,6-trimethoxyphenyl)-4-silacyclohexan-1-one (6). Compound 6 was synthesized by using the same procedure as described for the preparation of 1, starting from 27 (18.5 g, 56.7 mmol). The product was purified by bulb-to-bulb distillation (237− 240 °C/0.4 mbar), and the resulting solid distillate was recrystallized from n-hexane/ethyl acetate (1:1 v/v; slow cooling of a saturated boiling solution to −20 °C). The product was isolated by filtration and dried in vacuo (0.005 mbar, 20 °C, 4 h) to give 6 in 81% yield as a colorless crystalline solid (16.4 g, 46.0 mmol); mp 74 °C. 1H NMR (CD2Cl2): δ 1.49−1.66 (m, 4 H; SiCH2CH2C), 2.49−2.62 (m, 4 H; SiCH2CH2C), 3.71 (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.81 (s, 3 H; pOCH3, C6H2(OCH3)3), 6.10 (s, 2 H; H-3/H-5, C6H2(OCH3)3), 7.29−7.34 (m, 2 H; H-3/H-5, C6H5), 7.31−7.34 (m, 1 H; H-4, C6H5), 7.56−7.61 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 11.4 (SiCH 2 CH 2 C), 38.8 (SiCH 2 CH 2 C), 55.5 (o-OCH 3 , C6H2(OCH3)3), 55.6 (p-OCH3, C6H2(OCH3)3), 90.8 (C-3/C-5, C6H2(OCH3)3), 101.1 (C-1, C6H2(OCH3)3), 128.0 (C-3/C-5, C6H5), 129.2 (C-4, C6H5), 134.3 (C-2/C-6, C6H5), 138.1 (C-1, C6H5), 164.6 (C-4, C6H2(OCH3)3), 167.0 (C-2/C-6, C6H2(OCH3)3), 215.1 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ −15.0 ppm. Anal. Calcd for C20H24O4Si: C, 67.38; H, 6.79. Found: C, 67.35; H, 6.86. (4-(4-Methoxyphenyl)-4-phenyl-4-silacyclohexan-1-yl)amine (7). A suspension of activated Raney nickel in water (50 weight %, 1.00 g of suspension, 8.52 mmol of Raney nickel) was washed with methanol (3 × 10 mL), and the resulting powder was resuspended in methanol (10 mL). This suspension and a 7 M solution of ammonia in methanol (3.37 mL; 23.6 mmol of ammonia) were added sequentially in single portions at 20 °C to a stirred solution of 4 (1.00 g, 3.37 mmol) in methanol (20 mL), and the resulting mixture was heated in an autoclave at 100 °C under an atmosphere of hydrogen (30 bar) for 16 h. The mixture was then cooled to 20 °C and filtered through a pad of Celite, followed by elution with methanol (3 × 20 mL). The filtrate and the eluates were combined, the volatile components were removed under reduced pressure, and the oily residue was dissolved in diethyl ether (100 mL). Subsequently, a 2 M solution of hydrogen chloride in diethyl ether (2.00 mL, 4.00 mmol of HCl) was added at 0 °C within 10 min (formation of a precipitate), and the resulting suspension was then stirred at 0 °C for 30 min and at 20 °C for a further 2 h. The solid was separated by centrifugation (2300g, 5 min, 20 °C), and the supernatant was discarded. Subsequently, the solid was resuspended in diethyl ether (15 mL) and again isolated by centrifugation (2300g, 5 min, 20 °C). This procedure was repeated, and the product was then recrystallized from acetone/diethyl ether (5:1 v/v; slow cooling of a saturated boiling solution to −20 °C), isolated by filtration, and dried in vacuo (0.005 mbar, 20 °C, 3 h) to give 7·HCl in 78% yield as a colorless crystalline solid (879 mg, 2.63 mmol). Subsequently, a twophase mixture of 7·HCl (879 mg, 2.63 mmol), a 1 M aqueous solution of sodium hydroxide (18.0 mL, 18.0 mmol of NaOH), and diethyl ether (50 mL) was stirred at 20 °C for 30 min. The organic phase was 1024


Organometallics

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separated, the aqueous layer was extracted with diethyl ether (3 × 50 mL) and discarded, and the combined organic phases were dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation in vacuo to give 7 in 73% yield (with respect to 4) as a colorless oil (728 mg, 2.45 mmol); bp 253−254 °C/0.6 mbar. 1H NMR (CD2Cl2; data for two conformers (molar ratio 1:1.1); the dominating conformer is marked with an A, the minor conformer with a B): δ 1.03−1.14A,B (m, 2 H; SiCHHCH2C), 1.39−1.49A,B (m, 2 H; SiCHHCH2C), 1.40− 1.52 A,B (m, 2 H; SiCH 2 CHHC), 2.03−2.12 A,B (m, 2 H; SiCH2CHHC), 2.75−2.83A,B (m, 1 H; SiCH2CH2CH), 3.79A and 3.83B (s, 3 H; C6H4OCH3), 6.88−6.92A and 6.97−7.01B (m, 2 H; H3/H-5, C6H4OCH3), 7.31−7.37B and 7.39−7.44A (m, 2 H; H-3/H-5, C6H5), 7.33−7.37B and 7.40−7.44A (m, 1 H; H-4, C6H5), 7.39−7.43A and 7.56−7.60B (m, 2 H; H-2/H-6, C6H4OCH3), 7.47−7.51B and 7.62−7.68A ppm (m, 2 H; H-2/H-6, C6H5); signal for NH2 not detected. 13C NMR (CD2Cl2; data for two conformers (molar ratio 1:1.1); the dominating conformer is marked with an A, the minor conformer with a B): δ 9.5A,B (SiCH2CH2C), 34.13B and 34.14A (SiCH2CH2C), 53.2A and 53.3B (SiCH2CH2C), 55.31A and 55.33B (C6H4OCH3), 114.0A and 114.2B (C-3/C-5, C6H4OCH3), 126.1B and 128.0A (C-1, C6H4OCH3), 128.1B and 128.3A (C-3/C-5, C6H5), 129.47B and 129.54A (C-4, C6H5), 134.6B and 134.9A (C-2/C-6, C6H5), 136.09A and 136.4B (C-2/C-6, C6H4OCH3), 136.13A and 137.9B (C-1, C6H5), 161.08A and 161.14B ppm (C-4, C6H4OCH3). 29Si NMR (CD2Cl2; data for two conformers (molar ratio 1:1.1); the dominating conformer is marked with an A, the minor conformer with a B): δ −14.0A,B ppm. Anal. Calcd for C18H23NOSi: C, 72.68; H, 7.79; N, 4.71. Found: C, 72.36; H, 7.74; N, 4.72. Isopropyl(4-(4-methoxyphenyl)-4-phenyl-4-silacyclohexan-1-yl)amine (8). Compound 8 was synthesized by using the same procedure as described for the preparation of 7, starting from 4 (1.00 g, 3.37 mmol) and using isopropylamine (1.40 g, 23.7 mmol) instead of the 7 M solution of ammonia in methanol. The product was purified by bulb-to-bulb distillation in vacuo to give 8 in 61% yield as a colorless oil (700 mg, 2.06 mmol); bp 253−254 °C/0.3 mbar. 1H NMR (CD2Cl2; data for two conformers (molar ratio 1:1.6); the dominating conformer is marked with an A, the minor conformer with a B): δ 1.01−1.10A,B (m, 2 H; SiCHHCH2C), 1.018A and 1.020B (d, 3JHHA = 3 JHHB = 6.2 Hz, 6 H; CH(CH3)2), 1.34−1.42A,B (m, 2 H; SiCHHCH2C), 1.40−1.50A,B (m, 2 H; SiCH2CHHC), 2.01−2.09A,B (m, 2 H; SiCH2CHHC), 2.60−2.68A,B (m, 1 H; SiCH2CH2CH), 2.927A and 2.931B (sept, 3JHHA = 3JHHB = 6.2 Hz, 1 H; CH(CH3)2), 3.79A and 3.81B (s, 3 H; C6H4OCH3), 6.87−6.91A and 6.93−6.97B (m, 2 H; H-3/H-5, C6H4OCH3), 7.30−7.36B and 7.36−7.40A (m, 2 H; H3/H-5, C6H5), 7.33−7.36B and 7.36−7.41A (m, 1 H; H-4, C6H5), 7.39−7.43A and 7.51−7.55B (m, 2 H; H-2/H-6, C6H4OCH3), 7.47− 7.50B and 7.58−7.62A ppm (m, 2 H; H-2/H-6, C6H5); signal for NH not detected. 13C NMR (CD2Cl2; data for two conformers (molar ratio 1:1.6); the dominating conformer is marked with an A, the minor conformer with a B): δ 9.15A and 9.18B (SiCH2CH2C), 23.7A,B (C(CH3)2), 31.15A and 31.18B (SiCH2CH2C), 45.3A and 45.4B (C(CH3)2), 55.33A and 55.34B (C6H4OCH3), 55.5A and 55.6B (SiCH2CH2C), 113.9A and 114.1B (C-3/C-5, C6H4OCH3), 126.6B and 128.0A (C-1, C6H4OCH3), 128.1B and 128.3A (C-3/C-5, C6H5), 129.4B and 129.5A (C-4, C6H5), 134.7B and 134.9A (C-2/C-6, C6H5), 136.1A and 136.4B (C-2/C-6, C6H4OCH3), 136.5A and 137.9B (C-1, C6H5), 161.06A and 161.10B ppm (C-4, C6H4OCH3). 29Si NMR (CD2Cl2; data for two conformers (molar ratio 1:1.6); the dominating conformer is marked with an A, the minor conformer with a B): δ −13.0A,B ppm. HRMS (ESI): m/z calcd for [M + H]+ 340.2091, found 340.2088. (4-(2,4-Dimethoxyphenyl)-4-phenyl-4-silacyclohexan-1-yl)amine (9). A suspension of activated Raney nickel in water (50 weight %, 500 mg of suspension, 4.26 mmol of Raney nickel) was washed with methanol (3 × 10 mL), and the resulting powder was resuspended in methanol (10 mL). This suspension and a 7 M solution of ammonia in methanol (1.60 mL; 11.2 mmol of ammonia) were added sequentially in single portions at 20 °C to a stirred solution of 5 (520 mg, 1.59 mmol) in methanol (20 mL), and the resulting mixture was heated in

an autoclave at 100 °C under an atmosphere of hydrogen (30 bar) for 24 h. The mixture was then cooled to 20 °C and filtered through a pad of Celite, followed by elution with methanol (3 × 20 mL). The filtrate and the eluates were combined, the volatile components were removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation in vacuo to give 9 in 79% yield as a colorless oil (413 mg, 1.26 mmol); bp 267−279 °C/0.3 mbar. 1H NMR (CD2Cl2; data for four species (molar ratio 1:2.1:7.5:9.4) marked from A to D with decreasing concentration): δ 0.93−1.04A, 1.01−1.08C, 1.08−1.19B, and 1.13−1.18D (m, 2 H; SiCHHCH2C), 1.29−1.42B, 1.44−1.57A,D, and 1.67−1.74C (m, 2 H; SiCH2CHHC), 1.54−1.63A, 1.55−1.62C, 1.70− 1.72D, and 1.63−1.72B (m, 2 H; SiCHHCH2C), 1.94−2.05A, 1.97− 2.05C, 1.98−2.08B, and 2.07−2.14D (m, 2 H; SiCH2CHHC), 2.62− 2.71B, 2.76−2.84A, signals for C and D not detected (m, 1 H; SiCH2CH2CH), 3.64C and 3.72A,B,D (s, 6 H; C6H3(OCH3)2), 6.485B, 6.493D, 6.537C, and 6.547A (d, 3JHHA = 3JHHB = 3JHHC = 3JHHD = 8.3 Hz; 2 H, H-3/H-5, C6H3(OCH3)2), 7.25−7.36A,B,C,D (m, 2 H; H-3/H-5, C6H5), 7.26−7.35A,B,C,D (m, 1 H; H-4, C6H5), 7.28B, 7.335C, 7.342A, and 7.35D (t, 3JHHA = 3JHHB = 3JHHC = 3JHHD = 8.3 Hz, 1 H; H-4, C6H3(OCH3)2), 7.46−7.50C,D, 7.49−7.58A, and 7.64−7.72B ppm (m, 2 H; H-2/H-6, C6H5); signal for NH2 not detected. 13C NMR (CD2Cl2; data for four species (molar ratio 1:2.1:7.5:9.4) marked from A to D with decreasing concentration): δ 10.6C, 11.1D, 11.8A, and 12.1B (SiCH2CH2C), 33.2C, 34.0D, 34.3A, and 35.1B (SiCH2CH2C), 52.9A and 53.6B, signals for C and D not detected (SiCH2CH2C), 55.4C, 55.46A,D, and 55.51B (C6H3(OCH3)2), 103.91B, 103.94A, 104.1D, and 104.2C (C-3/C-5, C6H3(OCH3)2), 110.2C, 110.3A, 110.5D, and 112.1B (C-1, C6H3(OCH3)2), 127.73A, 127.77C, 127.87B, and 127.90D (C-3/ C-5, C6H5), 128.8A,B,C,D (C-4, C6H5), 132.3B, 132.38D, 132.44A, and 132.5C (C-4, C6H3(OCH3)2), 134.0D, 134.2C, 134.4A, and 134.7B (C2/C-6, C6H5), 138.3B, 138.8D, 139.1C, and 139.2A (C-1, C6H5), 165.8B, 166.1D, 166.3C, and 166.4A ppm (C-2/C-6, C6H3(OCH3)2). 29Si NMR (CD2Cl2; data for four species (molar ratio 1:2.1:7.5:9.4) marked from A to D with decreasing concentration): δ −16.3B, −15.0C, −14.9A, and −12.4D ppm. HRMS (ESI): m/z calcd for [M + H]+ 328.1727, found 328.1727. Isopropyl(4-(2,4-dimethoxyphenyl)-4-phenyl-4-silacyclohexan-1yl)amine (10). Compound 10 was synthesized by using the same procedure as described for the preparation of 9, using a suspension of activated Raney nickel in water (50 weight %, 500 mg of suspension, 4.26 mmol of Raney nickel), isopropylamine (674 mg, 11.4 mmol), and a solution of 5 (530 mg, 1.62 mmol) in methanol (20 mL). The reaction mixture was heated in an autoclave at 100 °C under an atmosphere of hydrogen (35 bar) for 27 h, and the product was purified by bulb-to-bulb distillation in vacuo to give 10 in 77% yield as a colorless oil (462 mg, 1.25 mmol); bp 273−275 °C/0.2 mbar. 1H NMR (CD2Cl2; data for four species (molar ratio 1:1.1:2.2:3.5) marked from A to D with decreasing concentration): δ 0.98−1.04C,D (m), 1.00B (d, 3JHHB = 6.2 Hz), and 1.02A (d, 3JHHA = 6.2 Hz) (6 H; CH(CH3)2), 0.98−1.06A, 1.00−1.08C, 1.07−1.16B, and 1.10−1.18D (m, 2 H; SiCHHCH2C), 1.47−1.56A, 1.53−1.61C, 1.59−1.67B, and 1.62−1.69D (m, 2 H; SiCHHCH2C), 1.26−1.37B, 1.47−1.57D, 1.48− 1.60A, and 1.66−1.75C (m, 2 H; SiCH2CHHC), 1.92−2.01A, 1.96− 2.05C, 2.04−2.13B, 2.07−2.14D (m, 2 H; SiCH2CHHC), 2.49−2.57B,D and 2.64−2.71A,C (m, 1 H; SiCH2CH2CH), 2.89−2.98C,D (m), 2.934B (sept, 3JHHB = 6.2 Hz), and 2.938A (sept, 3JHHA = 6.2 Hz) (1 H; CH(CH3)2), 3.711A, 3.714C,D, and 3.719B (s, 6 H; C6H3(OCH3)2), 6.480B, 6.482D, 6.52A, and 6.54C (d, 3JHHA = 3JHHB = 3JHHC = 3JHHD = 8.3 Hz, 2 H; H-3/H-5, C6H3(OCH3)2), 7.24−7.34A,B,C,D (m, 2 H; H3/H-5, C6H5), 7.24−7.36 (m, 1 H; H-4, C6H3(OCH3)2), 7.26− 7.33A,B,C,D (m, 1 H; H-4, C6H5), 7.51−7.57A,C and 7.63−7.68B,D ppm (m, 2 H; H-2/H-6, C6H5); signal for NH not detected. 13C NMR (CD2Cl2; data for four species (molar ratio 1:1.1:2.2:3.5) marked from A to D with decreasing concentration): δ 10.5C, 11.0D, 11.3A, and 12.1B (SiCH2CH2C), 23.4A,B,C,D (C(CH3)2), 31.0A 32.0B, 33.1C, and 34.0D (SiCH 2 CH 2 C), 45.4 A,B,C,D (C(CH 3 ) 2 ), 55.0 A,C and 56.3 B,D (SiCH2CH2C), 55.5A,B,C,D (C6H3(OCH3)2), 103.9A,B,C,D (C-3/C-5, C 6 H 3 (OCH 3 ) 2 ), 110.2 C , 110.6 A , 111.6 D , and 112.1 B (C-1, C6H3(OCH3)2), 127.75A, 127.78C, 127.8B, and 127.9D (C-3/C-5, C6H5), 128.81B, 128.83A, 128.92C, and 128.93D (C-4, C6H5), 132.3B, 1025


Organometallics

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132.39A,D, and 132.5C (C-4, C6H3(OCH3)2), 134.41A, 134.42C, 134.6D, and 134.7B (C-2/C-6, C6H5), 138.1D, 138.4B, 138.7C, and 139.2A (C-1, C6H5), 165.8B, 166.0D, and 166.3A,C ppm (C-2/C-6, C6H3(OCH3)2). 29 Si NMR (CD2Cl2; data for four species (molar ratio 1:1.1:2.2:3.5) marked from A to D with decreasing concentration): δ −16.2D, −15.2B, −15.1C, and −14.2A ppm. HRMS (ESI): m/z calcd for [M + H]+ 370.2197, found 370.2192. (4-Phenyl-4-(2,4,6-trimethoxyphenyl)-4-silacyclohexan-1-yl)amine (11). Compound 11 was synthesized by using the same procedure as described for the preparation of 9, using a suspension of activated Raney nickel in water (50 weight %, 1.50 g of suspension, 12.8 mmol of Raney nickel), a 7 M solution of ammonia in methanol (4.29 mL, 30.0 mmol of ammonia), and a solution of 6 (1.52 g, 4.26 mmol) in methanol (30 mL). The reaction mixture was heated in an autoclave at 100 °C under an atmosphere of hydrogen (100 bar) for 16 h, and the product was purified by bulb-to-bulb distillation in vacuo to give 11 in 74% yield as a colorless oil (1.13 g, 3.16 mmol); bp 248− 250 °C/0.02 mbar. 1H NMR (CD2Cl2; data for four species (molar ratio 1:1.3:23:28) marked from A to D with decreasing concentration): δ 0.91−1.01A, 0.99−1.06C, 1.07−1.15D, and 1.07−1.16B (m, 2 H; SiCHHCH2C), 1.47−1.55C, 1.53−1.60A, 1.59−1.66D, and 1.60−1.68B (m, 2 H; SiCHHCH2C), 1.30−1.40B, 1.33−1.43D, 1.45−1.56A, and 1.58−1.68C (m, 2 H; SiCH2CHHC), 1.95−2.03C, 1.96−2.04A, 1.98− 2.06B, and 2.08−2.13D (m, 2 H; SiCH2CHHC), 2.63−2.71B and 2.75− 2.83A, signals for C and D not detected (m, 1 H; SiCH2CH2CH), 3.715B and 3.718A, signals for C and D not detected (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.79B, 3.80D, 3.82C, and 3.83A (s, 3 H; p-OCH3, C6H2(OCH3)3), 6.07B, 6.08D, 6.11C, and 6.13A (s, 2 H; H-3/H-5, C6H2(OCH3)3), 7.26−7.31A,C and 7.30−7.36B,D (m, 2 H; H-3/H-5, C6H5), 7.28−7.34A,B,C,D (m, 1 H; H-4, C6H5), 7.40−7.55A,C and 7.65− 7.70B,D ppm (m, 2 H; H-2/H-6, C6H5); signal for NH2 not detected. 13 C NMR (CD2Cl2; data for four species (molar ratio 1:1.3:23:28) marked from A to D with decreasing concentration): δ 11.0C, 11.7D, 11.9A, and 12.1B (SiCH2CH2C), 30.1C, 31,1D, 34.5A, and 35.2B (SiCH2CH2C), 53.1A and 53.6B, signals for C and D not detected (SiCH2CH2C), 55.4A,B,C,D (o-OCH3, C6H2(OCH3)3), 55.45B.D and 55,52A,C (p-OCH3, C6H2(OCH3)3), 90.75B,D and 90.79A,C (C-3/C-5, C 6 H 2 (OCH 3 ) 3 ), 101.5 A , 102.0 C , 103.3 D , and 103.6 B (C-1, C6H2(OCH3)3), 127.70A, 127.72C, 127.80C, and 127.82B (C-3/C-5, C6H5), 128.71B and 128.73A, signals for C and D not detected (C-4, C6H5), 134.35A, 134.38C, 134.59D, and 134.62B (C-2/C-6, C6H5), 138.9B and 139.7A, signals for C and D not detected (C-1, C6H5), 164.04B, 164.04D, 164.1C, and 164.2A (C-4, C6H2(OCH3)3), 166.75B, 166.80D, 167.2C, and 167.3A ppm (C-2/C-6, C6H2(OCH3)3). 29Si NMR (CD2Cl2; data for four species (molar ratio 1:1.3:23:28) marked from A to D with decreasing concentration): δ −16.9B, −15.7D, −15.3A, and −14.8C. Anal. Calcd for C20H27NO3Si: C, 67.19; H, 7.61; N, 3.92. Found: C, 67.17; H, 7.65; N, 3.89. Isopropyl(4-phenyl-4-(2,4,6-trimethoxyphenyl)-4-silacyclohexan1-yl)amine (12). Compound 12 was synthesized by using the same procedure as described for the preparation of 9, using a suspension of activated Raney nickel in water (50 weight %, 500 mg of suspension, 4.26 mmol of Raney nickel), isopropylamine (662 mg, 11.2 mmol), and a solution of 6 (570 mg, 1.60 mmol) in methanol (20 mL). The reaction mixture was heated in an autoclave at 100 °C under an atmosphere of hydrogen (50 bar) for 16 h, and the product was purified by bulb-to-bulb distillation in vacuo to give 12 in 81% yield as a colorless oil (520 mg, 1.30 mmol); bp 285−287 °C/0.5 mbar. 1H NMR (CD2Cl2; data for four species (molar ratio 1:1.7:3.2:5.1) marked from A to D with decreasing concentration): δ 0.98−1.04C,D (m), 1.00B (d, 3JHHB = 6.2 Hz), and 1.02A (d, 3JHHA = 6.2 Hz) (6 H; CH(CH3)2), 0.96−1.05A,C, 1.06−1.15B, and 1.08−1.16D (m, 2 H; SiCHHCH2C), 1.45−1.53A, 1.52−1.59C, 1.57−1.65B, and 1.60−1.66D (m, 2 H; SiCHHCH2C), 1.26−1.36B, 1.46−1.58A, 1.48−1.58D, and 1.66−1.74C (m, 2 H; SiCH2CHHC), 1.92−2.01A, 1.98−2.05C, 2.04− 2.11B, and 2.07−2.13D (m, 2 H; SiCH2CHHC), 2.49−2.57B,D and 2.63−2.71A,C (m, 1 H; SiCH2CH2CH), 2.89−2.98C,D (m), 2.93B (sept, 3 JHHB = 6.2 Hz), and 2.94A (sept, 3JHHA = 6.2 Hz) (1 H; CH(CH3)2), 3.71A,B, 3.715D, and 3.717C (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.792B, 3.793D, 3.820A, and 3.824C (s, 3 H; p-OCH3, C6H2(OCH3)3), 6.069B,

6.070D, 6.11A, and 6.12C (s, 2 H; H-3/H-5, C6H2(OCH3)3), 7.26− 7.35A,B,C,D (m, 2 H; H-3/H-5, C6H5), 7.28−7.34A,B,C,D (m, 1 H; H-4, C6H5), 7.51−7.59A,C and 7.63−7.69B,D ppm (m, 2 H; H-2/H-6, C6H5); signal for NH not detected. 13C NMR (CD2Cl2; data for four species (molar ratio 1:1.7:3.2:5.1) marked from A to D with decreasing concentration): δ 10.7C, 11.1D, 11.4A, and 12.2B (SiCH2CH2C), 23.7 A , B, C ,D (C(CH 3 ) 2 ), 31.17 A , 32.22 B , 33.24 C , and 34.0 D (SiCH 2 CH 2 C), 45.3 A,B,C,D (C(CH 3 ) 2 ), 55.1 A,C and 56.3 B,D (SiCH2CH2C), 55.43A,C and 55.47B,D (o-OCH3, C6H2(OCH3)3), 55.53A,B,C,D (p-OCH3, C6H2(OCH3)3), 90.76D, 90.78B, and 90.80A,C (C-3/C-5, C6H2(OCH3)3), 101.5C, 102.0A, 103.1D, and 103.6B (C-1, C6H2(OCH3)3), 127.73A, 127.75C, 127.79B, and 127.9D (C-3/C-5, C6H5), 128.68B, 128.73A, 128.81D, and 128.82C (C-4, C6H5), 134.4A,C, 134.58D, and 134.56B (C-2/C-6, C6H5), 138.6D, 139.0B, 139.2C, and 139.7A (C-1, C6H5), 164.0B, 164.12D, 164.14A, and 164.2C (C-4, C6H2(OCH3)3), 166.80B, 166.81D, 167.24A, and 167.25C ppm (C-2/C6, C6H2(OCH3)3). 29Si NMR (CD2Cl2; data for four species (molar ratio 1:1.7:3.2:5.1) marked from A to D with decreasing concentration): δ −16.7D, −15.7B, −15.5C, and −14.6A ppm. HRMS (ESI): m/z calcd for [M + H]+ 400.2303, found 400.2303. 4-Chloro-4-phenyl-4-silacyclohexan-1-one (13). Method I. A 2 M solution of hydrogen chloride in diethyl ether (4.05 mL, 8.10 mmol of HCl) was added in a single portion at 20 °C to a stirred solution of 4 (40.0 mg, 135 μmol) in dichloromethane (10 mL), and the reaction mixture was then stirred at 20 °C for 60 h, until the cleavage of the MOP protecting group was complete (by GC/MS analysis). The volatile components were removed under reduced pressure, and the residue was demonstrated by NMR spectroscopic and GC/MS studies to be a mixture of 13 and methoxybenzene (see Figures S1−S5 in the Supporting Information). 1H NMR (CD2Cl2): δ 1.47−1.60 (m, 4 H; SiCH2CH2C), 2.58−2.68 and 2.76−2.85 (m, 4 H; SiCH2CH2C), 3.79 (s, 0.28 H; C6H5OCH3), 6.87−6.98 (m, 0.18 H; H-2/H-6, C6H5OCH3), 6.93−6.98 (m, 0.09 H; H-4, C6H5OCH3), 7.25−7.31 (m, 0.19 H; H-3/H-5, C6H5OCH3), 7.43−7.49 (m, 2 H; H-3/H-5, C6H5), 7.49−7.54 (m, 1 H; H-4, C6H5), 7.65−7.70 ppm (m, 2 H; H2/H-6, C6H5). 13C NMR (CD2Cl2): δ 13.3 (SiCH2CH2C), 37.5 (SiCH2CH2C), 55.4 (C6H5OCH3), 114.3 (C-2/C-6, C6H5OCH3), 120.9 (C-4, C6H5OCH3), 128.7 (C-3/C-5, C6H5), 129.7 (C-3/C-5, C6H5OCH3), 131.5 (C-4, C6H5), 132.9 (C-1, C6H5), 133.8 (C-2/C-6, C6H5), 161.5 (C-1, C6H5OCH3), 211.7 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ 15.2 ppm. Method II. A 2 M solution of hydrogen chloride in diethyl ether (650 μL, 1.30 mmol of HCl) was added in a single portion at 20 °C to a stirred solution of 5 (85.0 mg, 260 μmol) in dichloromethane (10 mL), and the reaction mixture was stirred at 20 °C for 30 min, until the cleavage of the DMOP protecting group was complete (by GC/ MS analysis). The volatile components were removed under reduced pressure, and the residue was demonstrated by NMR spectroscopy and GCIMS studies to be an equimolar mixture of 13 and 1,3dimethoxybenzene (see Figures S6−S10 in the Supporting Information). 1H NMR (CD2Cl2): δ 1.47−1.60 (m, 4 H; SiCH2CH2C), 2.58− 2.68 and 2.76−2.85 (m, 4 H; SiCH2CH2C), 3.78 (s, 6 H; C6H4(OCH3)2), 6.45−6.48 (m, 1 H; H-2, C6H4(OCH3)2), 6.48− 6.52 (m, 2 H; H-4/H-6, C6H4(OCH3)2), 7.15−7.21 (m, 1 H; H-5, C6H4(OCH3)2), 7.44−7.50 (m, 2 H; H-3/H-5, C6H5), 7.50−7.55 (m, 1 H; H-4, C6H5), 7.67−7.71 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 13.3 (SiCH2CH2C), 37.5 (SiCH2CH2C), 55.6 (C6H4(OCH3)2), 100.7 (C-2, C6H4(OCH3)2), 106.4 (C-4/C-6, C 6 H 4 (OC H 3 ) 2 ), 128.8 (C- 3 /C -5, C 6 H 5 ) , 1 3 0 . 2 ( C-5, C6H4(OCH3)2), 131.5 (C-4, C6H5), 132.9 (C-1, C6H5), 133.9 (C-2/ C-6, C 6 H 5 ), 161.3 (C-1/C-3, C 6 H 4 (OCH 3 ) 2 ), 211.7 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ 15.2 ppm. Method III. A 2 M solution of hydrogen chloride in diethyl ether (70.0 μL, 140 μmol of HCl) was added in a single portion at 20 °C to a stirred solution of 6 (50.0 mg, 140 μmol) in dichloromethane (10 mL), and the reaction mixture was then stirred at 20 °C for 5 min, until the cleavage of the TMOP protecting group was complete (by GC/MS anaylsis). The solvents were removed under reduced pressure, and the residue was demonstrated by NMR spectroscopy and GCIMS studies to be an equimolar mixture of 13 and 1,3,51026


Organometallics

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mbar. 1H NMR (CD2Cl2): δ 3.61 (s, 6 H; SiOCH3), 3.81 (s, 3 H; C6H4OCH3), 6.92−6.97 (m, 2 H; H-3/H-5, C6H4OCH3), 7.36−7.42 (m, 2 H; H-3/H-5, C6H5), 7.41−7.47 (m, 1 H; H-4, C6H5), 7.55−7.60 (m, 2 H; H-2/H-6, C6H4OCH3), 7.61−7.66 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 51.0 (SiOCH3), 55.4 (C6H4OCH3), 114.0 (C-3/C-5, C6H4OCH3), 123.6 (C-1, C6H4OCH3), 128.2 (C-3/ C-5, C6H5), 130.6 (C-4, C6H5), 133.2 (C-1, C6H5), 135.1 (C-2/C-6, C6H5), 136.7 (C-2/C-6, C6H4OCH3), 161.9 ppm (C-4, C6H4OCH3). 29 Si NMR (CD2Cl2): δ −28.9 ppm. Anal. Calcd for C15H18O3Si: C, 65.66; H, 6.61. Found: C, 65.57; H, 6.42. (2,4-Dimethoxyphenyl)dimethoxyphenylsilane (20). A 2.5 M solution of n-butyllithium in hexanes (154 mL, 385 mmol of nBuLi) was added dropwise at 20 °C within 1 h to a stirred mixture of 1,3-dimethoxybenzene (48.4 g, 350 mmol), TMEDA (44.7 g, 385 mmol), and n-hexane (150 mL). The resulting suspension was stirred at 20 °C for 16 h and then added to a stirred solution of 15 (69.4 g, 350 mmol) in diethyl ether (250 mL) at 20 °C within 1 h, and stirring was continued at 20 °C for 16 h. The resulting precipitate was filtered off, washed with diethyl ether (3 × 100 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by fractional distillation in vacuo to give 20 in 68% yield as a colorless liquid (72.9 g, 239 mmol); bp 172 °C/0.8 mbar. 1H NMR (CD2Cl2): δ 3.60 (s, 6 H; SiOCH3), 3.69 (s, 6 H; C6H3(OCH3)2), 6.56 (d, 3JHH = 8.3 Hz, 2 H; H-3/H-5, C6H3(OCH3)2), 7.28−7.37 (m, 2 H; H-3/H-5, C6H5), 7.31−7.39 (m, 1 H; H-4, C6H5), 7.38 (t, 3JHH = 8.3 Hz, 1 H; H-4, C6H3(OCH3)2), 7.57−7.61 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 51.2 (SiOCH3), 55.8 (C6H3(OCH3)2), 104.2 (C-3/C-5, C6H3(OCH3)2), 108.2 (C-1, C6H3(OCH3)2), 127.7 (C-3/C-5, C6H5), 129.7 (C-4, C6H5), 133.6 (C-4, C6H3(OCH3)2), 134.4 (C-2/C-6, C6H5), 136.2 (C-1, C6H5), 166.4 ppm (C-2/C-6, C6H3(OCH3)2). 29Si NMR (CD2Cl2): δ −29.8 ppm. Anal. Calcd for C16H20O4Si: C, 63.13; H, 6.62. Found: C, 63.06; H, 6.42. Dimethoxyphenyl(2,4,6-trimethoxyphenyl)silane (21). A 2.5 M solution of n-butyllithium in hexanes (154 mL, 386 mmol of n-BuLi) was added dropwise at 20 °C within 1 h to a stirred mixture of 1,3,5trimethoxybenzene (58.9 g, 350 mmol), TMEDA (44.7 g, 385 mmol), and n-hexane (150 mL). The resulting suspension was stirred at 20 °C for 16 h and then added to a stirred solution of 15 (69.4 g, 350 mmol) in diethyl ether (250 mL) at 20 °C within 1 h, and stirring was continued at 20 °C for a further 16 h. The resulting precipitate was filtered off, washed with diethyl ether (3 × 100 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by bulbto-bulb distillation in vacuo to give 21 in 67% yield as a colorless oil (78.5 g, 235 mmol); bp 164−165 °C/0.1 mbar. 1H NMR (CD2Cl2): δ 3.58 (s, 6 H; SiOCH3), 3.67 (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.83 (s, 3 H; p-OCH 3 , C 6 H 2 (OCH 3 ) 3 ), 6.11 (s, 2 H; H-3/H-5, C6H2(OCH3)3), 7.28−7.36 (m, 2 H; H-3/H-5, C6H5), 7.30−7.38 (m, 1 H; H-4, C6H5), 7.55−7.61 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 51.1 (SiOCH3), 55.6 (p-OCH3, C6H2(OCH3)3), 55.7 (o-OCH3, C6H2(OCH3)3), 90.9 (C-3/C-5, C6H2(OCH3)3), 99.8 (C-1, C6H2(OCH3)3), 127.6 (C-3/C-5, C6H5), 129.6 (C-4, C6H5), 134.4 (C-2/C-6, C 6 H 5 ), 136.6 (C-1, C 6 H 5 ), 165.0 (C-4, C6H2(OCH3)3), 167.6 ppm (C-2/C-6, C6H2(OCH3)3). 29Si NMR (CD2Cl2): δ −29.4 ppm. Anal. Calcd for C17H22O5Si: C, 61.05; H, 6.63. Found: C, 60.86; H, 6.60. (4-Methoxyphenyl)methyldivinylsilane (22). This compound was synthesized according to ref 5 (70% yield). (2,6-Dimethoxyphenyl)methyldivinylsilane (23). A solution of vinylmagnesium chloride in tetrahydrofuran (15 weight % CH2 CHMgCl, d = 0.97 g mL−1; 236 mL, 396 mmol of CH2CHMgCl) was added dropwise at 20 °C within 30 min to a stirred solution of 17 (45.7 g, 189 mmol) in tetrahydrofuran (100 mL), and the reaction mixture was heated under reflux for 1 h. The mixture was then cooled to 20 °C, followed by the addition of n-pentane (150 mL). The resulting precipitate was filtered off, washed with diethyl ether (3 × 100 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by fractional distillation in vacuo to give 23 in

trimethoxybenzene (see Figures S11−S15 in the Supporting Information). 1 H NMR (CD 2 Cl 2 ): δ 1.47−1.60 (m, 4 H; SiCH2CH2C), 2.58−2.68 and 2.76−2.85 (m, 4 H; SiCH2CH2C), 3.75 (s, 9 H; C6H3(OCH3)3), 6.08 (s, 3 H; H-2/H-4/H-6, C6H3(OCH3)3), 7.44−7.50 (m, 2 H; H-3/H-5, C6H5), 7.50−7.55 (m, 1 H; H-4, C6H5), 7.67−7.71 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 13.3 (SiCH2CH2C), 37.5 (SiCH2CH2C), 55.6 (C6H3(OCH3)3), 93.1 (C-2/C-4/C-6, C6H3(OCH3)3), 128.8 (C-3/C5, C6H5), 131.5 (C-4, C6H5), 132.9 (C-1, C6H5), 133.9 (C-2/C-6, C 6 H 5 ), 162.0 (C-1/C-3/C-5, C 6 H 3 (OCH 3 ) 3 ), 211.8 ppm (SiCH2CH2C). 29Si NMR (CD2Cl2): δ 15.2 ppm. Trimethoxymethylsilane (14). This compound was commercially available. Trimethoxyphenylsilane (15). This compound was commercially available. Dimethoxy(4-methoxyphenyl)methylsilane (16). This compound was synthesized according to ref 5 (71% yield). (2,6-Dimethoxyphenyl)dimethoxymethylsilane (17). A 2.5 M solution of n-butyllithium in hexanes (160 mL, 400 mmol of nBuLi) was added dropwise at 20 °C within 1 h to a stirred mixture of 1,3-dimethoxybenzene (50.8 g, 368 mmol), N,N,N′,N′-tetramethylenediamine (TMEDA; 46.9 g, 404 mmol), and n-hexane (170 mL). The resulting suspension was stirred at 20 °C for 16 h and then added to a stirred solution of 14 (50.0 g, 367 mmol) in diethyl ether (170 mL) at 20 °C within 1 h, and the reaction mixture was then heated under reflux for 2 h. The resulting precipitate was filtered off, washed with diethyl ether (3 × 70 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by fractional distillation in vacuo to give 17 in 71% yield as a colorless liquid (63.4 g, 262 mmol); bp 87 °C/0.3 mbar. 1H NMR (CD2Cl2): δ 0.32 (s, 3 H; SiCH3), 3.51 (s, 6 H; SiOCH3), 3.78 (s, 6 H; C6H3(OCH3)2), 6.54 (d, 3JHH = 8.3 Hz, 2 H; H-3/H-5, C6H3(OCH3)2), 7.34 ppm (t, 3JHH = 8.3 Hz, 1 H; H-4, C6H3(OCH3)2). 13C NMR (CD2Cl2): δ −1.4 (SiCH3), 50.7 (SiOCH3), 55.8 (C6H3(OCH3)2), 103.9 (C-3/C-5, C6H3(OCH3)2), 109.8 (C-1, C6H3(OCH3)2), 133.1 (C-4, C6H3(OCH3)2), 166.1 ppm (C-2/C-6, C6H3(OCH3)2). 29Si NMR (CD2Cl2): δ −15.3 ppm. Anal. Calcd for for C11H18O4Si: C, 54.52; H, 7.49. Found: C, 54.57; H 7.45. Dimethoxymethyl(2,4,6-trimethoxyphenyl)silane (18). A 2.5 M solution of n-butyllithium in hexanes (161 mL, 403 mmol of n-BuLi) was added dropwise at 20 °C within 1 h to a stirred mixture of 1,3,5trimethoxybenzene (61.8 g, 367 mmol), TMEDA (46.9 g, 404 mmol), and n-hexane (170 mL). The resulting suspension was stirred at 20 °C for 16 h and then added to a stirred solution of 14 (50.0 g, 367 mmol) in diethyl ether (170 mL) at 20 °C within 1 h, and the reaction mixture was then stirred at 20 °C for a further 16 h. The resulting precipitate was filtered off, washed with diethyl ether (3 × 100 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by fractional distillation in vacuo to give 18 in 77% yield as a colorless liquid (76.9 g, 282 mmol); bp 128 °C/0.3 mbar. 1H NMR (CD2Cl2): δ 0.29 (s, 3 H; SiCH3), 3.49 (s, 6 H; SiOCH3), 3.77 (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.82 (s, 3 H; p-OCH3, C6H2(OCH3)3), 6.10 ppm (s, 2 H; H-3/H-5, C6H2(OCH3)3). 13C NMR (CD2Cl2): δ −1.4 (SiCH3), 50.6 (SiOCH3), 55.6 (p-OCH3, C6H2(OCH3)3), 55.7 (o-OCH3, C6H2(OCH3)3), 90.7 (C-3/C-5, C6H2(OCH3)3), 101.6 (C1, C6H2(OCH3)3), 164.5 (C-4, C6H2(OCH3)3), 167.2 ppm (C-2/C-6, C6H2(OCH3)3). 29Si NMR (CD2Cl2): δ −15.0 ppm. Anal. Calcd for C12H20O5Si: C, 52.92; H, 7.40. Found: C, 52.90; H, 7.44. Dimethoxy(4-methoxyphenyl)phenylsilane (19). A solution of (4methoxyphenyl)magnesium bromide (prepared from magnesium turnings (7.66 g, 315 mmol) and 1-bromo-4-methoxybenzene (58.9 g, 315 mmol) in tetrahydrofuran (200 mL)) was added dropwise at 20 °C within 1 h to a stirred solution of 15 (59.5 g, 300 mmol) in diethyl ether (220 mL), and stirring was continued at 20 °C for 16 h. The resulting precipitate was filtered off, washed with diethyl ether (3 × 150 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by fractional distillation in vacuo to give 19 in 70% yield as a colorless liquid (57.9 g, 211 mmol); bp 131 °C/0.1 1027


Organometallics

Article

72% yield as a colorless liquid (32.2 g, 137 mmol); bp 78 °C/0.1 mbar. 1 H NMR (CD2Cl2): δ 0.48 (s, 3 H; SiCH3), 3.74 (s, 6 H; C6H3(OCH3)2), 5.69 (δA), 5.95 (δM), and 6.45 (δX) (6 H; CHX CHAHM, 3JAX = 20.4 Hz, 2JAM = 3.8 Hz, 3JMX = 14.5 Hz), 6.52 (d, 3JHH = 8.3 Hz, 2 H; H-3/H-5, C6H3(OCH3)2), 7.30 ppm (t, 3JHH = 8.3 Hz, 1 H; H-4, C6H3(OCH3)2). 13C NMR (CD2Cl2): δ −2.9 (SiCH3), 55.6 (C6H3(OCH3)2), 104.1 (C-3/C-5, C6H3(OCH3)2), 111.6 (C-1, C6H3(OCH3)2), 130.8 (SiCHCH2), 132.3 (C-4, C6H3(OCH3)2), 139.4 (SiCHCH2), 165.8 ppm (C-2/C-6, C6H3(OCH3)2). 29Si NMR (CD2Cl2): δ −21.7 ppm. Anal. Calcd for for C13H18O2Si: C, 66.62; H, 7.74. Found: C, 66.67; H, 7.73. Methyl(2,4,6-trimethoxyphenyl)divinylsilane (24). A solution of vinylmagnesium chloride in tetrahydrofuran (15 weight % CH2 CHMgCl, d = 0.97 g mL−1; 236 mL, 396 mmol of CH2CHMgCl) was added dropwise at 20 °C within 45 min to a stirred solution of 18 (51.3 g, 188 mmol) in tetrahydrofuran (120 mL), and the reaction mixture was heated under reflux for 1 h. The mixture was then cooled to 20 °C, followed by the addition of n-pentane (200 mL). The resulting precipitate was filtered off, washed with diethyl ether (3 × 100 mL), and discarded. The filtrate and wash solutions were combined, the solvents were removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation in vacuo to give 24 in 75% yield as a colorless oil (37.3 g, 141 mmol); bp 128 °C/0.1 mbar. 1 H NMR (CD2Cl2): δ 0.43 (s, 3 H; SiCH3), 3.72 (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.80 (s, 3 H; p-OCH3, C6H2(OCH3)3), 5.67 (δA), 5.93 (δM), and 6.42 (δX) (6 H; CHXCHAHM, 3JAX = 20.4 Hz, 2JAM = 3.9 Hz, 3JMX = 14.5 Hz), 6.08 ppm (s, 2 H; H-3/H-5, C6H2(OCH3)3). 13 C NMR (CD2Cl2): δ −2.8 (SiCH3), 55.5 (o-OCH3, C6H2(OCH3)3), 55.6 (p-OCH3, C6H2(OCH3)3), 90.9 (C-3/C-5, C6H2(OCH3)3), 102.9 (C-1, C6H2(OCH3)3), 130.5 (SiCHCH2), 139.7 (SiCHCH2), 164.1 (C-4, C6H2(OCH3)3), 166.8 ppm (C-2/C-6, C6H2(OCH3)3). 29 Si NMR (CD2Cl2): δ −22.1 ppm. Anal. Calcd for C14H20O3Si: C, 63.60; H, 7.62. Found: C, 63.62; H, 7.69. (4-Methoxyphenyl)phenyldivinylsilane (25). A solution of vinylmagnesium chloride in tetrahydrofuran (15 weight % CH2CHMgCl, d = 0.97 g mL−1; 183 mL, 307 mmol of CH2CHMgCl) was added dropwise at 20 °C within 1 h to a stirred solution of 19 (40.0 g, 146 mmol) in tetrahydrofuran (150 mL), and the reaction mixture was heated under reflux for 1 h. The mixture was then cooled to 20 °C, followed by the addition of n-pentane (250 mL) and water (200 mL). The organic layer was separated, the aqueous layer was extracted with dichloromethane (3 × 100 mL) and discarded, and the combined organic phases were dried over anhydrous sodium sulfate. The organic solvents were removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation in vacuo to give 25 in 90% yield as a colorless liquid (35.1 g, 132 mmol); bp 136 °C/0.1 mbar. 1H NMR (CDCl3): δ 3.82 (s, 3 H; C6H4OCH3), 5.81 (δA), 6.26 (δM), and 6.50 (δX) (6 H; CHXCHAHM, 3JAX = 20.2 Hz, 2JAM = 3.7 Hz, 3JMX = 14.6 Hz), 6.92−6.96 (m, 2 H; H-3/H-5, C6H4OCH3), 7.33−7.40 (m, 2 H; H-3/H-5, C6H5), 7.36−7.43 (m, 1 H; H-4, C6H5), 7.45−7.50 (m, 2 H; H-2/H-6, C6H4OCH3), 7.52−7.57 ppm (m, 2 H; H-2/H-6, C6H5). 13 C NMR (CDCl3 ): δ 55.0 (C 6H 4OCH 3), 113.7 (C-3/C-5, C6H4OCH3), 124.8 (C-1, C6H4OCH3), 127.8 (C-3/C-5, C6H5), 129.4 (C-4, C6H5), 134.2 (SiCHCH2), 134.6 (C-1, C6H5), 135.4 (C2/C-6, C6H5), 136.2 (SiCHCH2), 137.0 (C-2/C-6, C6H4OCH3), 160.8 ppm (C-4, C6H4OCH3). 29Si NMR (CDCl3): δ −20.8 ppm. Anal. Calcd for C17H18OSi: C, 76.64; H, 6.81. Found: C, 76.63; H, 6.63. (2,6-Dimethoxyphenyl)phenyldivinylsilane (26). A solution of vinylmagnesium chloride in tetrahydrofuran (15 weight % CH2 CHMgCl, d = 0.97 g mL−1; 211 mL, 354 mmol of CH2CHMgCl) was added dropwise at 20 °C within 45 min to a stirred solution of 20 (51.1 g, 168 mmol) in tetrahydrofuran (170 mL), and the reaction mixture was heated under reflux for 1 h. The mixture was then cooled to 20 °C, followed by the addition of n-pentane (200 mL) and water (200 mL). The organic layer was separated, the aqueous layer was extracted with dichloromethane (3 × 150 mL) and discarded, and the combined organic phases were dried over anhydrous sodium sulfate. The organic solvents were removed under reduced pressure, and the

residue was purified by bulb-to-bulb distillation in vacuo to give 26 in 76% yield as a colorless liquid (38.0 g, 128 mmol); bp 138 °C/0.1 mbar. 1H NMR (CD2Cl2): δ 3.63 (s, 6 H; C6H3(OCH3)2), 5.64 (δA), 6.10 (δM), and 6.64 (δX) (6 H; CHXCHAHM, 3JAX = 20.3 Hz, 2JAM = 3.9 Hz, 3JMX = 14.4 Hz), 6.55 (d, 3JHH = 8.3 Hz, 2 H; H-3/H-5, C6H3(OCH3)2), 7.27−7.34 (m, 2 H; H-3/H-5, C6H5), 7.29−7.36 (m, 1 H; H-4, C6H5), 7.36 (t, 3JHH = 8.3 Hz, 1 H; H-4, C6H3(OCH3)2), 7.46−7.52 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 55.6 (C6H3(OCH3)2), 104.4 (C-3/C-5, C6H3(OCH3)2), 110.3 (C-1, C6H3(OCH3)2), 127.6 (C-3/C-5, C6H5), 128.9 (C-4, C6H5), 132.9 (C4, C6H3(OCH3)2), 133.0 (SiCHCH2), 135.1 (C-2/C-6, C6H5), 137.0 (C-1, C6H5), 137.2 (SiCHCH2), 166.1 ppm (C-2/C-6, C6H3(OCH3)2). 29Si NMR (CD2Cl2): δ −24.9 ppm. Anal. Calcd for C18H20O2Si: C, 72.93; H, 6.80. Found: C, 73.02; H, 6.80. Phenyl(2,4,6-trimethoxyphenyl)divinylsilane (27). A solution of vinylmagnesium chloride in tetrahydrofuran (15 weight % CH2 CHMgCl, d = 0.97 g mL−1; 147 mL, 247 mmol of CH2CHMgCl) was added dropwise at 20 °C within 45 min to a stirred solution of 21 (39.1 g, 117 mmol) in tetrahydrofuran (90 mL), and the reaction mixture was heated under reflux for 1 h. The mixture was then cooled to 20 °C, followed by the addition of n-pentane (100 mL) and water (150 mL). The organic layer was separated, the aqueous layer was extracted with dichloromethane (3 × 100 mL) and discarded, and the combined organic phases were dried over anhydrous sodium sulfate. The organic solvents were removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation in vacuo to give 27 in 70% yield as a colorless oil (26.7 g, 81.8 mmol); bp 172−173 °C/0.2 mbar. 1H NMR (CD2Cl2): δ 3.62 (s, 6 H; o-OCH3, C6H2(OCH3)3), 3.83 (s, 3 H, p-OCH3, C6H2(OCH3)3), 5.63 (δA), 6.08 (δM), and 6.61 (δX) (6 H; CHXCHAHM, 3JAX = 20.4 Hz, 2JAM = 3.9 Hz, 3JMX = 14.5 Hz), 6.12 (s, 2 H; H-3/H-5, C6H2(OCH3)3), 7.27−7.33 (m, 2 H; H3/H-5, C6H5), 7.29−7.35 (m, 1 H; H-4, C6H5), 7.45−7.51 ppm (m, 2 H; H-2/H-6, C6H5). 13C NMR (CD2Cl2): δ 55.5 (o-OCH3, C6H2(OCH3)3), 55.6 (p-OCH3, C6H2(OCH3)3), 91.2 (C-3/C-5, C6H2(OCH3)3), 101.5 (C-1, C6H2(OCH3)3), 127.6 (C-3/C-5, C6H5), 128.8 (C-4, C6H5), 132.7 (SiCHCH2), 135.1 (C-2/C-6, C6H5), 137.4 (C-1, C6H5), 137.5 (SiCHCH2), 164.6 (C-4, C6H2(OCH3)3), 167.1 ppm (C-2/C-6, C6H2(OCH3)3). 29Si NMR (CD2Cl2): δ −25.2 ppm. Anal. Calcd for C19H22O3Si: C, 69.90; H, 6.79. Found: C, 69.89; H, 6.80. Crystal Structure Analyses. Suitable single crystals of 1, 3, 5, 6, 21, and 27 were obtained directly from the respective syntheses. The crystals were mounted in inert oil (perfluoropolyalkyl ether, ABCR) on a glass fiber and then transferred to the cold nitrogen gas stream of the diffractometer (Stoe IPDS, graphite-monochromated Mo Kα radiation (λ = 0.71073 Å)). The structures were solved by direct methods (SHELXS-97).10 All non-hydrogen atoms were refined anisotropically (SHELXL-97).10 A riding model was employed in the refinement of the CH hydrogen atoms. CCDC-975473 (1), CCDC975474 (3), CCDC-975475 (5), CCDC-975476 (6), CCDC-975477 (21), and CCDC-975478 (27) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam. ac.uk/data_request/cif.

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ASSOCIATED CONTENT

S Supporting Information *

Data for the crystal structure analyses of compounds 1, 3, 5, 6, 21, and 27 (Table S1) and 1H, 13C, and 29Si NMR spectra and GC/MS spectra of the mixtures 13/H-MOP, 13/H-DMOP, and 13/H-TMOP (Figures S1−S15). This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest. 1028


Organometallics

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REFERENCES

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amines Containing the Silicon Protecting Groups MOP (4

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