Indium-Silicon Combined Lewis Acid Catalyst for Direct Allylation of Alcohols with Allyltrimethylsilane in Non-Halogenated Solvent

Abstract

A direct allylation of alcohols is effectively catalyzed by a combined Lewis acid system of InCl₃ and Me₃SiBr. This system allows use of non-halogenated solvents such as hexane and application to a wide range of alcohols.

indium - alcohols - direct allylation - Lewis acid - silicon

References

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1d Bisaro F. Prestat G. Vitale M. Poli G. Synlett  2002,  1823 

1e For the asymmetric transformation of alcohol mediated by titanium(IV) complex, see: Braun M. Kotter W. Angew. Chem. Int. Ed.  2004,  43:  514 

2 Rubin M. Gevorgyan V. Org. Lett.  2001,  3:  2705 

3 Yasuda M. Saito T. Ueba M. Baba A. Angew. Chem. Int. Ed.  2004,  43:  1414 

4

Non-halogenated solvents such as hexane, THF and DMF provided less satisfactory results in the allylation of benzhydrol (1b, see ref. 3).

5a Onishi Y. Ito T. Yasuda M. Baba A. Eur. J. Org. Chem.  2002,  1578 

5b Onishi Y. Ito T. Yasuda M. Baba A. Tetrahedron  2002,  58:  8227 

6a Miyai T. Onishi Y. Baba A. Tetrahedron  1999,  55:  1017 

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8 In the allylation of 1-phenylethanol (1a) using B(C₆F₅)₃, elimination of alcohol 1a to form styrene could readily occur (see ref. 3). Only a dimeric ether was obtained by InBr₃, see: Kim SH. Shin C. Pae AN. Koh HY. Chang MH. Chung BY. Cho YS. Synthesis  2004,  1581 

For recent reviews on silicon Lewis acids, see:

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9b Oishi M. In Lewis Acids in Organic Synthesis   Vol. 1:  Yamamoto H. Wiley-VCH; Weinheim: 2000.  p.355-393  

10 The allylation of alcohol in the presence of Yb(OTf)₃ was not promoted at all, although the enhancement of the Lewis acidity using the combination of Yb(OTf)₃ and Me₃SiCl was reported, see: Yamanaka M. Nishida A. Nakagawa M. Org. Lett.  2000,  2:  159 

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General Methods.
IR spectra were recorded as thin films on a HORIBA FT-720 spectrophotometer. ¹H NMR and ¹³C NMR spectra were obtained with TMS as internal standard. Mass spectra were recorded on a JEOL JMS-DS303. MALDI-TOF MS was measured on an Applied Biosystem Voyager RP using dithranol matrix. Column chromatography was performed on silica gel (Merck C60). Bulb-to-bulb distillation (Kugelrohr) was accomplished in a Sibata GTO-250RS at the oven temperature and pressure indicated. Yields were determined by ¹H NMR using internal standards.
Typical Procedure for Allylation of 1a (Table 2, Entry 1).
To a mixture of InCl₃ (0.05 mmol) and 1-phenylethanol (1a, 1.0 mmol) in hexane (1 mL) was added allyltrimethylsilane (2, 2.0 mmol) and Me₃SiBr (0.1 mmol) under nitrogen. The reaction mixture was stirred under the reaction conditions noted in the text. The resulting mixture was poured into Et₂O (50 mL) and aq NaHCO₃ (30 mL). The solution was extracted with Et₂O and the organic layer was dried over MgSO₄. The evaporation of the ether solution gave the crude product, which was analyzed by NMR.
Typical Procedure for Allylation by Slow Addition of 1a (Table 2, Entry 2).
To a mixture of InCl₃ (0.05 mmol), Me₃SiBr (0.1 mmol) and allyltrimethylsilane (2, 3.0 mmol) in hexane (1 mL) was slowly added a solution of 1-phenylethanol (1a, 1.0 mmol) in hexane (1 mL) for 10 min at 50 °C under nitrogen. The reaction mixture was stirred for 110 min. The resulting mix-ture was poured into Et₂O (50 mL) and aq NaHCO₃ (30 mL). The solution was extracted with Et₂O and the organic layer was dried over MgSO₄. The evaporation of the ether solution gave the crude product, which was analyzed by NMR.
Product Data.
All products 3a-f are known compounds. The products
3a-c showed spectra in an excellent agreement with our previous reported data. [3] The spectral data of 3d was in an excellent agreement with the sample which is commercially available. Our spectral data of 3e [14] and 3f [15] are shown below.
4-Ferrocenyl-1-pentene ( 3e): according to the typical procedure, this compound was prepared from 1e, 2, InCl₃ and Me₃SiBr to give the product as a brown liquid after chromatography(hexane). Further purification was performed by distillation under reduced pressure; bp 95 °C/0.1 mmHg. IR:(neat): 1639 (C=C) cm^-1. ¹H NMR (400 MHz, CDCl₃): δ = 5.78 (dddd, J = 17.9, 10.4, 7.7, 6.5 Hz, 1 H, 2-H), 5.00 (ddt, J = 17.9, 1.2, 1.2 Hz, 1 H, 1-H^A), 4.99 (ddt, J = 10.4, 1.2, 1.2 Hz, 1 H, 1-H^B), 4.12-4.11 (m, 5 H, C₅H₅), 4.06 (s, 4 H, C₅H₄), 2.55 (ddq, J = 8.7, 5.1, 6.8 Hz, 1 H, 4-H), 2.36 (dddt, J = 13.8, 6.5, 5.1, 1.2 Hz, 1 H, 3-H^A), 2.07 (dddt, J = 13.8, 8.7, 7.7, 1.2 Hz, 1 H, 3-H^B), 1.21 (d, J = 6.8 Hz, 3 H, 5-H₃). ¹³C NMR (100 MHz, CDCl₃): δ = 137.38 (d, C-2), 115.71 (t, C-1), 95.33 (s, ipso-carbon in C₅H₄), 68.35 (d, C₅H₅), 66.96 (d), 66.92 (d), 66.80 (d), 65.93 (d), 43.08 (t, C-3), 32.94 (d, C-4), 20.01 (q, C-5). MS (EI, 70 eV): m/z (%) = 254 (58)[M⁺], 213 (100) [M⁺ - CH₂CH=CH₂], 121 (23) [M⁺ - C₅H₄CH(CH₃)CH₂CH=CH₂]. HRMS (EI, 70 eV): m/z calcd for C₁₅H₁₈Fe: 254.0758 [M⁺]; found: 254.0752. Anal. Calcd for C₁₅H₁₈Fe: C, 70.89; H, 7.14. Found: C, 70.60; H, 7.09.
3-Allylcyclohexene ( 3f): according to the typical procedure, this compound was prepared from 1f, 2, InCl₃ and Me₃SiBr to give the product as a colorless liquid after distillation under reduced pressure; bp 110 °C/100 mmHg. IR:(neat): 1643 (C=C) cm^-1. ¹H NMR (400 MHz, CDCl₃): δ = 5.81 (ddt, J = 16.9, 10.1, 7.0 Hz, 1 H, 3-CH₂CH=CH₂), 5.68 (ddd, J = 10.1, 5.8, 3.6 Hz, 1 H, 1-H), 5.59 (dd, J = 10.1, 2.1 Hz, 1 H, 2-H), 5.05-4.99 (m, 2 H, 3-CH₂CH=CH ₂), 2.17-2.12 (m, 1 H, 3-H), 2.06 (ddd, J = 13.0, 6.3, 6.3 Hz, 2 H, 3-CH ^AH^BCH=CH₂), 2.05 (ddd, J = 13.0, 6.3, 6.3 Hz, 2 H, 3-CH^A H ^BCH=CH₂), 2.00-1.94 (m, 2 H, 6-H₂), 1.80-1.68 (m, 2 H, 4-H^A and 5-H^A), 1.58-1.47 (m, 1 H, 5-H^B), 1.28-1.18 (m, 1 H, 4-H^B). ¹³C NMR (100 MHz, CDCl₃): δ = 137.25 (d, 3-CH₂ CH=CH₂), 131.39 (d, C-2), 127.2 (d, C-1), 115.71 (t, 3-CH₂CH=CH₂), 40.65 (t, 3-CH₂CH=CH₂), 35.01 (d, C-3), 28.80 (t, C-4), 25.27 (t, C-6), 21.41 (t, C-5). MS (EI, 70 eV): m/z (%) = 122 (6) [M⁺], 81 (100) [M⁺ - CH₂CH=CH₂], 79 (22). HRMS (EI, 70 eV): m/z calcd for C₉H₁₄: 122.1096 [M⁺]; found: 122.1091.

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Elimination of alcohols 1e occurred in the presence of combined Lewis acid in hexane to give polyvinylferrocene rather than the desired product. Polyvinylferrocene was identified by MALDI-TOF MS analysis.

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Large-Scale Synthesis of 3a.
To a mixture of InCl₃ (5 mmol), Me₃SiBr (10 mmol) and allyltrimethylsilane 2 (300 mmol) in hexane (100 mL) was slowly added a solution of 1a (100 mmol) in hexane (100 mL) for 1 h under nitrogen at 50 °C. After further stirring for 1 h at 50 °C, aq NaHCO₃ (100 mL) was added to the reaction mixture. The mixture was extracted with Et₂O and the organic layer was dried over MgSO₄. The evaporation of the ether solution followed by the distillation (34 °C/1.5 mmHg) gave the allylated product 3a in 84% yield (12.3g).

14 Jong S.-J. Fang J.-M. J. Org. Chem.  2001,  66:  3533 

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