Synthesis and Characterization of New Trifunctional

Publication Date (Web): September 10, 2009. Copyright © 2009 American .... of the Formula Type Me4−nSi[CH2Si(SiMe3)3]n (n = 1−3) and Derivatives...
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Organometallics 2009, 28, 5765–5770 DOI: 10.1021/om9005577

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Synthesis and Characterization of New Trifunctional Tetraorganylsilanes of the Formula Types MeSi(CH2X)3, MeSi(CH2X)2CH2X0 , and MeSi(CH2X)(CH2X0 )CH2X00 Dennis Troegel, Frank M€ oller, Christian Burschka, and Reinhold Tacke* Institut f€ ur Anorganische Chemie, Universit€ at W€ urzburg, Am Hubland, D-97074 W€ urzburg, Germany Received June 29, 2009

A series of novel trifunctional tetraorganylsilanes of the general formula types MeSi(CH2X)3 (X=I (2), OAc (3), OH (4), Br (5), (4-methylphenyl)sulfonyloxy (6), phthalimido (7), NH2 3 HBr (8 3 3HBr)), MeSi(CH2X)2CH2X0 (X=SH, X0 =OH (9); X=Cl, X0 =OAc (11); X=SAc, X0 = OAc (12)), and MeSi(CH2X)(CH2X0 )CH2X00 (X=Cl, X0=OAc, X00=SAc (rac-13); X=phthalimido, X0=OAc, X00= SAc (rac-14); X=N3, X0 =OAc, X00 =SAc (rac-15)) was synthesized, starting from MeSi(CH2Cl)3 (1). All the compounds synthesized was characterized by elemental analyses (C, H, N, S) and NMR studies (1H, 13C, 15N (rac-15 only), 29Si). In addition, compounds 4 and 6 were structurally characterized by single-crystal X-ray diffraction. The title compounds are claimed to be versatile starting materials for the synthesis of a variety of novel C-functional organosilicon compounds.

Introduction Recently, we have reported on the synthesis of a series of tetrafunctional tetraorganylsilanes of the general formula type Si(CH2X)4 (X = functional group),1-3 starting from Si(CH2Cl)4. Generally, tetrakis(chloromethyl)silane,4 (chloromethyl)silanes can be synthesized from the corresponding chlorosilanes and (chloromethyl)lithium, generated in situ from bromochloromethane and n-butyllithium in tetrahydrofuran.4,5 (Chloromethyl)silanes with four Si-C bonds are stable against air and moisture and therefore can be easily handled in synthesis. Owing to their reactive electrophilic SiCH2Cl groups, they have a great synthetic potential for the preparation of multifunctional organosilicon compounds. In this context, we have recently synthesized a series of tris(mercaptomethyl)silanes, starting from their corresponding tris(chloromethyl)silanes.3,5g In continuation of these studies, we have been interested in the synthetic potential

of tris(chloromethyl)methylsilane,3 MeSi(CH2Cl)3 (1), for the preparation of new trifunctional tetraorganylsilanes of the general formula types MeSi(CH2X)3, MeSi(CH2X)2CH2X0 , and MeSi(CH2X)(CH2X0 )CH2X00 . We report here on the synthesis of compounds 2-7, 8 3 3HBr, and 9, starting from 1, and their characterization by multinuclear NMR spectroscopy and single-crystal X-ray diffraction (4 and 6 only). In addition, we report on the failed synthesis of rac-10.

*To whom correspondence should be addressed. Phone: þ49-931-3185250. Fax: þ49-931-888-4609. E-mail: [email protected]. (1) Ilg, R.; Troegel, D.; Burschka, C.; Tacke, R. Organometallics 2006, 25, 548–551. (2) Klap€ otke, T. M.; Krumm, B.; Ilg, R.; Troegel, D.; Tacke, R. J. Am. Chem. Soc. 2007, 129, 6908–6915. (3) Apfel, U.-P.; Troegel, D.; Halpin, Y.; Uhlemann, U.; Schmitt, M.; Popp, J.; G€ orls, H.; Dunne, P.; Venkatesan, M.; Coey, M.; Vos, J. G.; Tacke, R.; Weigand, W. Manuscript in preparation. (4) Daiss, J. O.; Barth, K. A.; Burschka, C.; Hey, P.; Ilg, R.; Klemm, K.; Richter, I.; Wagner, S. A.; Tacke, R. Organometallics 2004, 23, 5193– 5197. (5) (a) Kobayashi, T.; Pannell, K. H. Organometallics 1990, 9, 2201– 2203. (b) Kobayashi, T.; Pannell, K. H. Organometallics 1991, 10, 1960– 1964. (c) Sharma, S.; Pannell, K. H. Organometallics 1993, 12, 3979–3983. (d) Handmann, V. I.; Bertermann, R.; Burschka, C.; Tacke, R. J. Organomet. Chem. 2000, 613, 19–25. (e) Tacke, R.; Kornek, T.; Heinrich, T.; Burschka, C.; Penka, M.; P€ ulm, M.; Keim, C.; Mutschler, E.; Lambrecht, G. J. Organomet. Chem. 2001, 640, 140–165. (f) Hassler, K.; Hummeltenberg, R.; Tekautz, G. Eur. J. Inorg. Chem. 2004, 4259–4265. (g) Troegel, D.; Walter, T.; Burschka, C.; Tacke, R. Organometallics 2009, 28, 2756–2761.

Syntheses. Compounds 2-7 and 8 3 3HBr were synthesized according to Scheme 1, starting from tris(chloromethyl)methylsilane (1). Thus, reaction of 1 with sodium iodide afforded tris(iodomethyl)methylsilane (2) (93% yield).

r 2009 American Chemical Society

Published on Web 09/10/2009

Results and Discussion

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Organometallics, Vol. 28, No. 19, 2009 Scheme 1

Treatment of 1 with sodium acetate gave tris(acetoxymethyl)methylsilane (3) (86% yield), which upon methanolysis, in the presence of acetyl chloride, yielded tris(hydroxymethyl)methylsilane (4) (87% yield). Subsequent treatment of 4 with phosphorus tribromide afforded tris(bromomethyl)methylsilane 5 (86% yield). Attempts to convert 4 with 4-methylbenzenesulfonyl chloride, in the presence of triethylamine, into tris(((4-methylphenyl)sulfonyloxy)methyl)methylsilane (6) failed. Instead, a quantitative transformation (GC analysis) of 4 into 1 was observed; after purification by column chromatography on silica gel, compound 1 was isolated in 68% yield. However, the target compound 6 could be obtained by treatment of 4 with 4-methylbenzenesulfonic acid anhydride (77% yield). Treatment of 1 with potassium phthalimide yielded methyltris(phthalimidomethyl)silane (7) (90% yield), which upon hydrolysis with concentrated hydrobromic acid afforded tris(aminomethyl)methylsilane trihydrobromide (8 3 3HBr) (77% yield). The attempted transformation of the ammonium salt 8 3 3HBr into the corresponding triamine 8 by treatment with

Troegel et al. Scheme 2

triethylamine or sodium methoxide in polar organic solvents resulted in an Si-C bond cleavage to yield methylamine. The sensitivity of the Si-CH2NH2 group against nucleophiles has already been reported for related (aminomethyl)silanes;6 however, this reactivity profile has not yet been fully understood. (Hydroxymethyl)bis(mercaptomethyl)methylsilane (9) was synthesized according to Scheme 2, starting from 1. In a first experiment, compound 1 was treated with 1 molar equiv of sodium acetate in refluxing dimethylformamide (reaction time, 24 h) to afford a mixture consisting of 1 (32 mol %), (acetoxymethyl)bis(chloromethyl)methylsilane (11) (48 mol %), bis(acetoxymethyl)(chloromethyl)methylsilane (MeSi(CH2OAc)2CH2Cl) (18 mol %), and 3 (2 mol %) (GC analysis). The percentage of the targeted intermediate 11 could be increased by using a catalytic amount of 18-crown6 and milder reaction conditions (treatment of 1 with sodium acetate in dimethylformamide at 20 °C; reaction time, 5 days) to give a mixture consisting of 1 (20 mol %), 11 (60 mol %), and MeSi(CH2OAc)2CH2Cl (20 mol %), without formation of detectable amounts of 2 (GC analysis). After separation and purification by column chromatography on silica gel, compound 11 was isolated in 50% yield. Subsequent treatment of 11 with potassium thioacetate afforded (acetoxymethyl)bis(acetylthiomethyl)methylsilane (12) (89% yield), which upon reduction with lithium aluminum hydride, followed by aqueous workup, furnished 9 (94% yield). To synthesize rac-(aminomethyl)(hydroxymethyl)(mercaptomethyl)methylsilane (rac-10) with its three different functional groups, two different routes were studied, starting from rac-(acetoxymethyl)(acetylthiomethyl)(chloromethyl)methylsilane (rac-13) (Scheme 3). Compound rac-13, which also contains three different functional groups, was obtained by treatment of 11 with 1 molar equiv of potassium thioacetate in tetrahydrofuran. Under the reaction conditions chosen (temperature, 20 °C; reaction time, 5 days), a mixture of the starting material 11 (20 mol %), the target compound rac-13 (66 mol %), and the disubstituted product 12 (14 mol %) (GC analysis) was obtained, which upon chromatographic separation and purification on silica gel afforded rac-13 in 61% yield. Subsequent treatment of rac-13 with potassium phthalimide furnished rac-(acetoxymethyl)(acetylthiomethyl)methyl(phthalimidomethyl)silane (rac-14) in 85% yield. Likewise, treatment of rac-13 (6) (a) Goubeau, J.; Fromm, H. D. Z. Anorg. Allg. Chem. 1962, 317, 41–53. (b) Anderson, W. K.; Kasliwal, R.; Houston, D. M.; Wang, Y.; Narayanan, V. L.; Haugwitz, R. D.; Plowman, J. J. Med. Chem. 1995, 38, 3789–3797. (c) Van Dorsselaer, V.; Schirlin, D.; Marchal, P.; Weber, F.; Danzin, C. Bioorg. Chem. 1996, 24, 178–193.

Article

Organometallics, Vol. 28, No. 19, 2009 Scheme 3

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Table 1. Crystal Data and Experimental Parameters for the Crystal Structure Analyses of 4 and 6

empirical formula formula mass, g mol-1 collection T, K λ(Mo KR), A˚ cryst syst space group (no.) a, A˚ b, A˚ c, A˚ R, deg β, deg γ, deg V, A˚3 Z D(calcd), g cm-3 μ, mm-1 F(000) cryst dimens, mm 2θ range, deg index ranges

4

6

C4H12O3Si 136.23 100(2) 0.71073 monoclinic P21/c (14) 7.2400(2) 8.4818(3) 11.9853(4) 90 99.429(2) 90 726.05(4) 4 1.246 0.254 296 0.4  0.3  0.3 5.70-56.88 -9 e h e 9, -10 e k e 11, -15 e l e 16 19 701 1808 0.0353 1808 0 83 1.060 0.0317/0.2428 0.0234 0.0660 þ0.446/-0.204

C25H30O9S3Si 598.76 193(2) 0.71073 triclinic P1(2) 12.673(3) 15.215(3) 15.689(3) 88.88(3) 87.78(3) 76.12(3) 2934.7(10) 4 1.355 0.341 1256 0.5  0.3  0.3 5.20-58.20 -17 e h e 17, -19 e k e 19, -21 e l e 21 42 507 14 389 0.0368 14 389 149 803 1.020 0.0525/0.5925 0.0438 0.1084 þ0.331/-0.336

no. of collected reflns no. of indep reflns Rint no. of reflns used no. of restraints no. of params Sa weight params a/bb R1c [I > 2σ(I)] wR2d (all data) max./min. residual electron density, e A˚-3 P a S = { [w(Fo2 - Fc 2)2]/(n - p)}0.5; n = no. of reflections; p = no. of 2 2 b -1 2 (Fo2) þ (aP)2 þ bP, = [max(F parameters. o ,0) þ 2Fc ]/3. P w = σP P with P c d 2 2 2 P 2 2 0.5 R1 = ||Fo| - |Fc||/ |Fo|. wR2 = { [w(Fo - Fc ) ]/ [w(Fo ) ]} .

with sodium azide afforded rac-(acetoxymethyl)(acetylthiomethyl)(azidomethyl)methylsilane (rac-15) in 74% yield. However, all attempts to convert the trifunctional intermediates rac-14 and rac-15 into rac-10 failed. Different synthetic methods were applied (Scheme 3) using various reaction conditions, but in all cases Si-CH2NH2 bond cleavage was observed. Compounds 2, 3, 5, 9, 11, 12, rac-13, and rac-15 were isolated as liquids, whereas 4, 6, 7, and 8 3 3HBr were obtained as crystalline solids. The identities of all these compounds were established by elemental analyses (C, H, N, S) and NMR studies (1H, 13C, 15N (rac-15 only), 29Si). In addition, compounds 4 and 6 were characterized by crystal structure analyses. Crystal Structure Analyses. Compounds 4 and 6 were structurally characterized by single-crystal X-ray diffraction. The crystal data and the experimental parameters used for these studies are given in Table 1. The molecular structure of 4 is depicted in Figure 1; selected interatomic distances and bond angles are given in the figure legend (for further details concerning the crystal structure analyses, see the Supporting Information). The bond lengths and angles of 4 and 6 are all in the expected ranges and therefore do not need any further comments, except for the hydrogen-bonding system observed in the crystal of 4. As shown in Figure 2, all three OH groups of

Figure 1. Molecular structure of 4 in the crystal (probability level of displacement ellipsoids 50%). Selected bond distances (A˚) and angles (deg): Si-C1 1.8790(10), Si-C2 1.8792(10), Si-C3 1.8763(9), Si-C4 1.8612(10), O1-C1 1.4328(12), O2-C2 1.4396(11), O3-C3 1.4413(11); C1-Si-C2 104.57(4), C1-Si-C3 110.69(4), C1-Si-C4 113.24(4), C2-Si-C3 110.06(4), C2-Si-C4 111.19(5), C3-Si-C4 107.12(4), Si-C1-O1 112.37(6), Si-C2-O2 109.87(6), Si-C3-O3 112.29(6).

the tris(hydroxymethyl)silane 4 act as both proton donor and proton acceptor to form a three-dimensional hydrogen-bond-

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Figure 2. Three-dimensional hydrogen-bonding network in the crystal of 4.7 The hydrogen atoms (except for the OH atoms) are omitted for clarity. Bond distances (A˚) and angles (deg): O1-H1 0.743(15), H1 3 3 3 O2A 1.996(15), O1 3 3 3 O2A 2.7138(10), O1-H1 3 3 3 O2A 162.7(16); O2-H2 0.803(14), H2 3 3 3 O3B 1.916(14), O2 3 3 3 O3B 2.7190(10), O2-H2 3 3 3 O3B 177.4(14); O3-H3 0.776(14), H3 3 3 3 O1C 1.933(14), O3 3 3 3 O1C 2.7028(11), O3-H3 3 3 3 O1C 171.0(15).

ing network consisting of intermolecular O-H 3 3 3 O hydrogen bonds.7

Conclusions Multifunctional tetraorganylsilanes are versatile building blocks for synthetic organosilicon chemistry. In this study, we have evaluated the potential of tris(chloromethyl)methylsilane, MeSi(CH2Cl)3, as a starting material for the preparation of a series of new trifunctional tetraorganylsilanes. We have succeeded in synthesizing compounds of the formula types MeSi(CH2X)3 (X = I, OAc, OH, Br, (4methylphenyl)sulfonyloxy, phthalimido), MeSi(CH2X)2CH2X0 (X = SH, X0 = OH; X = Cl, X0 = OAc; X = SAc, X0 =OAc), and MeSi(CH2X)(CH2X0 )CH2X00 (X=Cl, X0 = OAc, X00 =SAc; X=pthalimido, X0 =OAc, X00 =SAc; X= N3, X0 =OAc, X00 =SAc). These trifunctional tetraorganylsilanes are claimed to be versatile starting materials for the synthesis of a variety of novel C-functional organosilicon compounds, and the silanes MeSi(CH2OH)3 and MeSi(CH2SH)3 and related compounds of this type are expected to be interesting tripodal ligands for transition metals.

Experimental Section General Procedures. All syntheses were carried out under dry nitrogen. The organic solvents used were dried and purified according to standard procedures and stored under dry nitrogen. A B€ uchi GKR-51 apparatus was used for the bulb-to-bulb distillations. Melting points were determined with a B€ uchi melting point B-540 apparatus using samples in sealed glass capillaries. The 1H, 13C, 15N, and 29Si NMR spectra were recorded at 23 °C on a Bruker DRX-300 (1H, 300.1 MHz; 13C, 75.5 MHz; 15N, 30.4 MHz; 29Si, 59.6 MHz) or a Bruker Avance 500 NMR spectrometer (1H, 500.1 MHz; 13C, 125.8 MHz; 29Si, (7) The hydrogen-bonding system was analyzed by using the program system PLATON: Spek, A. L. PLATON; University of Utrecht: Utrecht, The Netherlands, 1998. (8) Troegel, D. Dissertation, University of W€urzburg, 2009.

Troegel et al. 99.4 MHz). CDCl3, CD2Cl2, or [D6]DMSO was used as the solvent. Chemical shifts (ppm) were determined relative to internal CHCl3 (1H, δ 7.24; CDCl3), internal CDCl3 (13C, δ 77.0; CDCl3), internal CHDCl2 (1H, δ 5.32; CD2Cl2), internal CD2Cl2 (13C, δ 53.8; CD2Cl2), internal [D5]DMSO (1H, δ 2.49; [D6]DMSO), internal [D6]DMSO (13C, δ 39.5; [D6]DMSO), external H2NC(O)H (90% in [D6]DMSO; 15N, δ -268.0; CDCl3), or external TMS (29Si, δ 0; CDCl3, CD2Cl2, [D6]DMSO). Analysis and assignment of the 1H NMR data were supported by 1H,1H COSY, 13C,1H HMQC, and 13C,1H HMBC experiments. Assignment of the 13C NMR data was supported by DEPT 135, 13C,1H HMQC, and 13C,1H HMBC experiments. Assignment of the 15N NMR data was supported by 15N,1H HMQC and 15N,1H HMBC experiments. Preparation of Tris(chloromethyl)methylsilane (1). Method A: This compound was synthesized according to refs 3 and 8. Method B: 4-Methylbenzenesulfonyl chloride (9.25 g, 48.5 mmol) and triethylamine (4.91 g, 48.5 mmol) were added at 20 °C successively in single portions to a stirred solution of 4 (2.00 g, 14.7 mmol) in acetonitrile (100 mL), and the resulting mixture was stirred at 20 °C for 19 h. The solvent was removed under reduced pressure, dichloromethane (100 mL) and water (100 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with dichloromethane (2  100 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by column chromatography on silica gel (silica gel, 32-63 μm (ICN 02826); eluent, n-hexane/ethyl acetate (2:1 (v/v))), followed by bulb-to-bulb distillation (45 °C/0.1 mbar) to give 1 in 68% yield as a colorless liquid (1.92 g, 10.0 mmol). 1 H NMR (300.1 MHz, CDCl3): δ 0.37 (s, 3 H, SiCH3), 3.01 (s, 6 H, SiCH2Cl). 13C NMR (75.5 MHz, CDCl3): δ -8.6 (SiCH3), 25.3 (SiCH2Cl). 29Si NMR (59.6 MHz, CDCl3): δ 2.5. Anal. Calcd for C4H9Cl3Si: C, 25.08; H, 4.74. Found: C, 25.29; H, 4.77. Preparation of Tris(iodomethyl)methylsilane (2). Compound 1 (412 mg, 2.15 mmol) was added in a single portion at 20 °C to a stirred solution of sodium iodide (1.83 g, 12.2 mmol) in acetone (16 mL), and the resulting mixture was stirred at 20 °C for 24 h. The solvent was removed under reduced pressure, n-pentane (100 mL) and water (50 mL) were added to the residue, the organic layer was separated, and the aqueous phase was extracted with n-pentane (2  100 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation (85 °C/0.03 mbar) to give 2 in 93% yield as a yellowish liquid (929 mg, 1.99 mmol). 1 H NMR (500.1 MHz, CDCl3): δ 0.45 (s, 3 H, SiCH3), 2.24 (s, 6 H, SiCH2I). 13C NMR (125.8 MHz, CDCl3): δ -17.6 (SiCH2I), -4.8 (SiCH3). 29Si NMR (99.4 MHz, CDCl3): δ 5.1. Anal. Calcd for C4H9I3Si: C, 10.31; H, 1.95. Found: C, 10.50; H, 2.07. Preparation of Tris(acetoxymethyl)methylsilane (3). Compound 1 (5.00 g, 26.1 mmol) was added in a single portion at 20 °C to a stirred suspension of sodium acetate (9.68 g, 118 mmol) in dimethylformamide (65 mL), and the resulting mixture was stirred under reflux for 16 h. The solvent was removed by distillation (45 °C/10 mbar), diethyl ether (100 mL) and water (100 mL) were added to the residue, the organic layer was separated, and the aqueous phase was extracted with diethyl ether (3  100 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation (105 °C/0.3 mbar) to give 3 in 86% yield as a yellowish liquid (5.87 g, 22.4 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.17 (s, 3 H, SiCH3), 2.01 (s, 9 H, C(O)CH3), 3.87 (s, 6 H, SiCH2O). 13C NMR (75.5 MHz, CDCl3): δ -8.2 (SiCH3), 20.5 (C(O)CH3), 53.9 (SiCH2O), 171.6 (C(O)CH3). 29Si NMR (59.6 MHz, CDCl3): δ -4.1. Anal. Calcd for C10H18O6Si: C, 45.79; H, 6.92. Found: C, 45.66; H, 6.63.

Article Preparation of Tris(hydroxymethyl)methylsilane (4). Acetyl chloride (540 mg, 6.88 mmol) was added dropwise at 20 °C within 1 min to a stirred solution of 3 (12.3 g, 46.9 mmol) in methanol (700 mL), and the resulting mixture was heated under reflux for 18 h. The solvent was removed under reduced pressure, and the oily residue was crystallized from boiling acetonitrile (30 mL; slow cooling to -20 °C and crystallization over a period of 24 h). The product was isolated by removal of the mother liquor via a syringe and then dried in vacuo (0.05 mbar, 20 °C, 3 h) to give 4 in 87% yield as a colorless crystalline solid (5.54 g, 40.7 mmol). 1H NMR (300.1 MHz, [D6]DMSO): δ -0.01 (s, 3 H, SiCH3), 3.26 (d, 3JHH=4.2 Hz, 6 H, SiCH2O), 3.92 (t, 3JHH=4.2 Hz, 3 H, OH). 13C NMR (75.5 MHz, [D6]DMSO): δ -9.2 (SiCH3), 49.5 (SiCH2O). 29Si NMR (59.6 MHz, [D6]DMSO): δ -5.4. Anal. Calcd for C4H12O3Si: C, 35.27; H, 8.88. Found: C, 35.22; H, 8.88. Preparation of Tris(bromomethyl)methylsilane (5). Phosphorus tribromide (19.9 g, 73.5 mmol) was added dropwise at 20 °C within 5 min to a stirred suspension of 4 (5.00 g, 36.7 mmol) in toluene (200 mL), and the resulting mixture was stirred at 20 °C for 20 h. The solvent was removed under reduced pressure, n-pentane (500 mL) and water (500 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with n-pentane (2  300 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation (55 °C/0.04 mbar) to give 5 in 86% yield as a colorless liquid (10.2 g, 31.4 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.41 (s, 3 H, SiCH3), 2.68 (s, 6 H, SiCH2Br). 13C NMR (75.5 MHz, CDCl3): δ -7.0 (SiCH3), 12.0 (SiCH2Br). 29Si NMR (59.6 MHz, CDCl3): δ 2.0. Anal. Calcd for C4H9Br3Si: C, 14.79; H, 2.79. Found: C, 14.95; H, 2.83. Preparation of Tris(((4-methylphenyl)sulfonyloxy)methyl)methylsilane (6). A mixture of 4 (1.00 g, 7.34 mmol) and dichloromethane (40 mL) was added dropwise at 0 °C within 15 min to a stirred solution of 4-methylbenzenesulfonic acid anhydride (7.91 g, 24.2 mmol) in dichloromethane (20 mL), and the resulting mixture was stirred at 20 °C for 19 h. Water (20 mL) was added dropwise at 20 °C within 15 min, and the resulting mixture was stirred at 20 °C for 3 h. The organic layer was separated, extracted with water (2  20 mL), and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the residue was crystallized from boiling n-hexane/ethyl acetate (2:1 (v/v)) (60 mL; slow cooling to -20 °C and crystallization over a period of 3 days). The product was isolated by removal of the mother liquor via a syringe and then dried in vacuo (0.1 mbar, 20 °C, 3 h) to give 6 in 77% yield as a colorless crystalline solid (3.39 g, 5.66 mmol); mp 85-86 °C. 1 H NMR (300.1 MHz, CD2Cl2): δ 0.21 (s, 3 H, SiCH3), 2.46 (s, 9 H, CCH3), 3.75 (s, 6 H, SiCH2O), 7.37-7.40 (m, 6 H, H-3/H-5, C6H4), 7.69-7.73 (m, 6 H, H-2/H-6, C6H4). 13C NMR (75.5 MHz, CD2Cl2): δ -9.6 (SiCH3), 21.8 (CCH3), 57.8 (SiCH2O), 128.5 (C-2/C-6, C6H4), 130.4 (C-3/C-5, C6H4), 131.7 (C-1, C6H4), 145.8 (C-4, C6H4). 29Si NMR (59.6 MHz, CD2Cl2): δ -2.3. Anal. Calcd for C25H30O9S3Si: C, 50.15; H, 5.05; S, 16.07. Found: C, 50.12; H, 4.95; S, 16.32. Preparation of Methyltris(phthalimidomethyl)silane (7). Compound 1 (3.00 g, 15.7 mmol) was added in a single portion to a stirred mixture consisting of potassium phthalimide (8.70 g, 47.0 mmol), 18-crown-6 (522 mg, 1.97 mmol), and dimethylformamide (80 mL), and the resulting mixture was stirred at 20 °C for 19 h. The solvent was removed by distillation (45 °C/ 10 mbar), dichloromethane (100 mL) and water (100 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with dichloromethane (2  100 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was crystallized from dichloromethane (50 mL; crystallization by slow evaporation of

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the solvent at 20 °C over a period of 25 days). The product was isolated by removal of the mother liquor via a syringe and then dried in vacuo (0.1 mbar, 20 °C, 3 h) to give 7 in 90% yield as a colorless crystalline solid (7.40 g, 14.1 mmol); mp 194-195 °C. 1H NMR (300.1 MHz, CDCl3): δ 0.22 (s, 3 H, SiCH3), 3.44 (s, 6 H, SiCH2N), 7.61-7.64 (m, 6 H, H-3/H-4, C6H4), 7.69-7.72 (m, 6 H, H-2/H-5, C6H4). 13C NMR (75.5 MHz, CDCl3): δ -4.7 (SiCH3), 26.9 (SiCH2N), 123.0 (C-2/C-5, C6H4), 132.2 (C-1/C-6, C6H4), 133.7 (C-3/C-4, C6H4), 168.5 (CdO). 29Si NMR (59.6 MHz, CDCl3): δ 1.8. Anal. Calcd for C28H21N3O6Si: C, 64.23; H, 4.04; N, 8.03. Found: C, 63.99; H, 4.05; N, 7.95. Preparation of Tris(aminomethyl)methylsilane Trihydrobromide (8 3 3HBr). A suspension of 7 (7.50 g, 14.3 mmol) in concentrated hydrobromic acid (48%; 85 mL) was heated under reflux for 24 h. The resulting mixture was diluted with water (45 mL) and cooled to 0 °C, and the precipitate was then removed by filtration and washed with cold water (100 mL). The filtrate and the wash solution were combined, the solvent was removed under reduced pressure, the residue was suspended in methanol (50 mL), the resulting suspension was covered with diethyl ether (40 mL), and the two-phase mixture was then kept undisturbed at 20 °C for 24 h. The precipitate was isolated by filtration, washed with diethyl ether (3  10 mL), and dried in vacuo (0.05 mbar, 20 °C, 3 h) to give 8 3 3HBr in 77% yield as a colorless crystalline solid (4.14 g, 11.0 mmol); mp 276-277 °C (dec). 1H NMR (500.1 MHz, [D6]DMSO): δ 0.42 (s, 3 H, SiCH3), 2.60 (q, 3JHH = 6.0 Hz, 6 H, SiCH2N), 7.80 (br s, 9 H, NH3). 13C NMR (125.8 MHz, [D6]DMSO): δ -7.0 (SiCH3), 23.9 (SiCH2N). 29Si NMR (99.4 MHz, [D6]DMSO): δ 1.0. Anal. Calcd for C4H18Br3N3Si: C, 12.78; H, 4.83; N, 11.18. Found: C, 12.87; H, 4.81; N, 10.99. Preparation of (Hydroxymethyl)bis(mercaptomethyl)methylsilane (9). A solution of 12 (5.60 g, 19.0 mmol) in diethyl ether (80 mL) was added dropwise at 0 °C within 2 h to a stirred suspension of lithium aluminum hydride (5.41 g, 143 mmol) in diethyl ether (170 mL), and the resulting mixture was stirred at 0 °C for 90 min and then at 20 °C for a further 21 h. Subsequently, hydrochloric acid (2 M, 110 mL) was added dropwise at 0 °C within 2 h under stirring, and the resulting mixture was then warmed to 20 °C, followed by the addition of water (280 mL) and diethyl ether (280 mL). The organic phase was separated, the aqueous phase was extracted with diethyl ether (2  280 mL) and discarded, the combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation (75-80 °C/0.03 mbar) to give 9 in 94% yield as a colorless liquid (3.02 g, 17.9 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.18 (s, 3 H, SiCH3), 1.33 (t, 3JHH=7.3 Hz, 2 H, SH), 1.73 (s, 1 H, OH), 1.81 (d, 3JHH=7.3 Hz, 4 H, SiCH2S), 3.57 (s, 2 H, SiCH2O). 13C NMR (75.5 MHz, CDCl3): δ -8.0 (SiCH3), 3.3 (SiCH2S), 52.3 (SiCH2O). 29Si NMR (59.6 MHz, CDCl3): δ 1.4. Anal. Calcd for C4H12OS2Si: C, 28.54; H, 7.18; S, 38.09. Found: C, 28.66; H, 7.16; S, 38.33. Preparation of (Acetoxymethyl)bis(chloromethyl)methylsilane (11). Compound 1 (10.0 g, 52.2 mmol) was added in a single portion to a stirred mixture consisting of sodium acetate (4.28 g, 52.2 mmol), 18-crown-6 (185 mg, 700 μmol), and dimethylformamide (75 mL), and the resulting mixture was stirred at 20 °C for 5 days. The solvent was removed by distillation (45 °C/ 10 mbar), diethyl ether (200 mL) and water (200 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with diethyl ether (2200 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by column chromatography on silica gel (silica gel, 32-63 μm (ICN 02826); eluent, n-hexane/ethyl acetate (9:1 (v/v))). The relevant fractions (GC analysis) were combined, and the solvent was removed under reduced pressure to give 11 in 50% yield as a colorless liquid (5.57 g, 25.9 mmol). 1H NMR (300.1 MHz,

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CDCl3): δ 0.29 (s, 3 H, SiCH3), 2.03 (s, 3 H, C(O)CH3), 2.96 (s, 4 H, SiCH2Cl), 3.94 (s, 2 H, SiCH2O). 13C NMR (75.5 MHz, CDCl3): δ -8.5 (SiCH3), 20.5 (C(O)CH3), 25.9 (SiCH2Cl), 53.2 (SiCH2O), 171.6 (C(O)CH3). 29Si NMR (59.6 MHz, CDCl3): δ 0.2. Anal. Calcd for C6H12Cl2O2Si: C, 33.50; H, 5.62. Found: C, 33.61; H, 5.42. Preparation of (Acetoxymethyl)bis(acetylthiomethyl)methylsilane (12). Compound 11 (4.65 g, 21.6 mmol) was added in a single portion at 20 °C to a stirred suspension of potassium thioacetate (7.40 g, 64.8 mmol) in tetrahydrofuran (150 mL), and the resulting mixture was stirred at 20 °C for 24 h. The solvent was removed under reduced pressure, water (250 mL) and diethyl ether (250 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with diethyl ether (2  250 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by bulb-to-bulb distillation (120140 °C/0.03 mbar) to give 12 in 89% yield as a yellowish liquid (5.66 g, 19.2 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.13 (s, 3 H, SiCH3), 1.99 (s, 3 H, OC(O)CH3), 2.17 (s, 4 H, SiCH2S), 2.28 (s, 6 H, SC(O)CH3), 3.79 (s, 2 H, SiCH2O). 13C NMR (75.5 MHz, CDCl3): δ -6.6 (SiCH3), 9.9 (SiCH2S), 20.6 (OC(O)CH3), 30.0 (SC(O)CH3), 54.2 (SiCH2O), 171.4 (OC(O)CH3), 195.6 (SC(O)CH3). 29Si NMR (59.6 MHz, CDCl3): δ 1.1. Anal. Calcd for C10H18O4S2Si: C, 40.79; H, 6.16; S, 21.78. Found: C, 41.05; H, 6.12; S, 21.05. Preparation of rac-(Acetoxymethyl)(acetylthiomethyl)(chloromethyl)methylsilane (rac-13). Compound 11 (5.53 g, 25.7 mmol) was added in a single portion at 20 °C to a stirred suspension of potassium thioacetate (2.93 g, 25.7 mmol) in tetrahydrofuran (60 mL), and the resulting mixture was stirred at 20 °C for 5 days. The solvent was removed under reduced pressure, water (100 mL) and diethyl ether (100 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with diethyl ether (2  100 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by column chromatography on silica gel (silica gel, 32-63 μm (ICN 02826); eluent, n-hexane/ethyl acetate (9:1 (v/v))). The relevant fractions (GC analysis) were combined, and the solvent was removed under reduced pressure to give rac-13 in 61% yield as a colorless liquid (3.99 g, 15.7 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.22 (s, 3 H, SiCH3), 2.02 (s, 3 H, OC(O)CH3), 2.24 (s, 2 H, SiCH2S), 2.31 (s, 3 H, SC(O)CH3), 2.88 (s, 2 H, SiCH2Cl), 3.88 (s, 2 H, SiCH2O). 13 C NMR (75.5 MHz, CDCl3): δ -7.5 (SiCH3), 9.1 (SiCH2S), 20.6 (OC(O)CH3), 26.9 (SiCH2Cl), 30.0 SC(O)CH3), 53.7 (SiCH2O), 171.5 (OC(O)CH3), 195.7 (SC(O)CH3). 29Si NMR (59.6 MHz, CDCl3): δ 0.8. Anal. Calcd for C8H15ClO3SSi: C, 37.71; H, 5.93; S, 12.58. Found: C, 37.52; H, 5.97; S, 12.04. Preparation of rac-(Acetoxymethyl)(acetylthiomethyl)methyl(phthalimidomethyl)silane (rac-14). Compound rac-13 (3.92 g, 15.4 mmol) was added in a single portion at 20 °C to a mixture consisting of potassium phthalimide (2.85 g, 15.4 mmol), 18-crown-6 (157 mg, 594 μmol), and dimethylformamide (30 mL), and the resulting mixture was stirred at 20 °C for 29 h. The solvent was removed by distillation (45 °C/10 mbar), water (130 mL) and diethyl ether (130 mL) were added to the residue, the organic phase was separated, and the aqueous phase was extracted with diethyl ether (3  130 mL) and discarded. The combined organic extracts were dried over anhydrous sodium sulfate, the solvent was removed under reduced pressure, and the residue was purified by column chromatography on silica gel (silica gel, 32-63 μm (ICN 02826); eluent, n-hexane/

Troegel et al. ethyl acetate (1:1 (v/v))). The relevant fractions (GC analysis) were combined, and the solvent was removed under reduced pressure to give rac-14 in 85% yield as a colorless liquid (4.79 g, 13.1 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.19 (s, 3 H, SiCH3), 1.91 (s, 3 H, OC(O)CH3), 2.26 (s, 5 H, SiCH2S, SC(O)CH3), 3.24 (δA) and 3.27 (δB) (2JAB = 15.6 Hz, 2 H, SiCHAHBN), 3.85 (δA) and 3.89 (δB) (2JAB = 13.8 Hz, 2 H, SiCHAHBO), 7.64-7.67 (m, 2 H, H-3/H-4, C6H4), 7.75-7.78 (m, 2 H, H-2/H-5, C6H4). 13C NMR (75.5 MHz, CDCl3): δ -6.2 (SiCH3), 10.2 (SiCH2S), 20.4 (OC(O)CH3), 25.3 (SiCH2N), 29.9 (SC(O)CH3), 54.8 (SiCH2O), 123.0 (C-2/C-5, C6H4), 132.0 (C-1/ C-6, C6H4), 133.8 (C-3/C-4, C6H4), 168.3 (NC(O)C), 171.5 (OC(O)CH3), 195.7 (SC(O)CH3). 29Si NMR (59.6 MHz, CDCl3): δ 0.4. Anal. Calcd for C16H19NO5SSi: C, 52.58; H, 5.24; N, 3.83; S, 8.77. Found: C, 52.74; H, 5.32; N, 3.89; S, 8.79. Preparation of rac-(Acetoxymethyl)(acetylthiomethyl)(azidomethyl)methylsilane (rac-15). Compound rac-13 (4.54 g, 17.8 mmol) was added in a single portion at 20 °C to a stirred suspension of sodium azide (3.65 g, 56.1 mmol) and sodium carbonate (230 mg, 2.17 mmol) in acetone (10 mL), and the resulting mixture was stirred at 20 °C for 8 days. The precipitate was removed by filtration, washed with acetone (25 mL), and discarded. The filtrate and the wash solution were combined, the solvent was removed under reduced pressure, and the residue was purified by column chromatography on silica gel (silica gel, 32-63 μm (ICN 02826); eluent, n-hexane/ethyl acetate (9:1 (v/v))). The relevant fractions (GC analysis) were combined, and the solvent was removed under reduced pressure to give rac15 in 74% yield as a yellowish liquid (3.42 g, 13.1 mmol). 1H NMR (300.1 MHz, CDCl3): δ 0.19 (s, 3 H, SiCH3), 2.03 (s, 3 H, OC(O)CH3), 2.19 (s, 2 H, SiCH2S), 2.31 (s, 3 H, SC(O)CH3), 2.96 (s, 2 H, SiCH2N), 3.84 (s, 2 H, SiCH2O). 13C NMR (75.5 MHz, CDCl3): δ -7.3 (SiCH3), 9.2 (SiCH2S), 20.6 (OC(O)CH3), 30.0 (SC(O)CH3), 38.4 (SiCH2N), 53.9 (SiCH2O), 171.5 (OC(O)CH3), 195.7 (SC(O)CH3). 15N NMR (30.4 MHz, CDCl3): δ -321.3 (SiCH2NNN), -169.2 (SiCH2NNN), -129.6 (SiCH2NNN). 29Si NMR (59.6 MHz, CDCl3): δ 0.3. Anal. Calcd for C8H15N3O3SSi: C, 36.76; H, 5.78; N, 16.08; S, 12.27. Found: C, 36.93; H, 5.87; N, 16.17; S, 11.66. Crystal Structure Analyses. Suitable single crystals of 4 and 6 were obtained by crystallization from acetonitrile (4) or nhexane/ethyl acetate (6) at -20 °C. 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 (4: Bruker Nonius KAPPA APEX II CCD system with Montel mirror, Mo KR radiation (λ=0.71073 A˚); 6: Stoe IPDS, graphite-monochromated Mo KR radiation (λ= 0.71073 A˚)). The structures were solved by direct methods (SHELXS-97).9 All non-hydrogen atoms were refined anisotropically (SHELXL-97).9 A riding model was employed in the refinement of the hydrogen atoms. Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with The Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC-743928 (4) and CCDC-743929 (6). Copies of the data can be obtained free of charge on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax, (þ44)1223/336033; e-mail, [email protected]. ac.uk). Supporting Information Available: Crystallographic data for 4 and 6. This material is available free of charge via the Internet at http://pubs.acs.org. (9) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.