Synthesis and Some Physical Properties of New Organometallic Compounds Containing Si and Sn Atoms †
1
INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
2
CIC-PBA, 1900 La Plata, Argentina
3
CONICET, C1425FQB Ciudad Autónoma de Buenos Aires, Argentina
*
Author to whom correspondence should be addressed.
†
Presented at the 22nd International Electronic Conference on Synthetic Organic Chemistry, 15 November–15 December 2018. Available Online: https://sciforum.net/conference/ecsoc-22.
Proceedings 2019, 9(1), 62; https://doi.org/10.3390/ecsoc-22-05687
Published: 14 November 2018
(This article belongs to the Proceedings of 22nd International Electronic Conference on Synthetic Organic Chemistry)
Abstract
:This paper reports the synthesis of two new organotin hydrides containing a (phenyldimethylsilyl)methyl ligand. It was found that the reaction of (phenyldime thylsilyl) methylmagnesium bromide in ether afforded ((phenyldimethylsilyl)methyl) trimethyltin (3) (72%), and with (−)-menthyldimethyltin bromide (4) gave (((phenyl dimethylsilyl)methyl)(1R,2R,5R) -2-isopropyl-5-methylcyclohexyl)dimethyltin (5) (84%). Bromo dealkylation of 3 with bromine in MeOH led to ((phenyldimethylsilyl)methyl)dimethyltin bromide (6) (82%), which upon reduction with LiAlH4 yielded ((phenyldimethyl silyl)methyl)dimethyltin hydride (7) (95%). The best method for obtaining the corresponding bromostannylated derivative of compound 5, i.e., (((phenyldimethylsilyl) methyl)(1R,2R,5R)-2-isopropyl-5-methylcyclohexyl) methyltin bromide (8) was the exchange reaction between 4 and HgBr2 that led to 8 with 90% yield. The reduction of bromide 8 with LiAlH4 gave a diastereomeric mixture of (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl-5- methylcyclohexyl)methyltin hydride (9). Some physical properties and 1H, 13C, and 119Sn NMR of the new organotin hydrides, as well as that of their intermediate precursors are included.
1. Introduction
Organotin hydrides have found many applications in organic synthesis, not only as reducing reagents, but also as intermediates in the generation of carbon–carbon bonds, and for the preparation of compounds, such as vinylstannanes, which are invaluable starting materials for cross-coupling reactions [1,2,3]. In previous studies, we have shown that the size of organic ligands attached to a tin atom affects not only the reactivity, but also the stereoselectivity of the reactions of these compounds [4]. We have also reported the synthesis of tin compounds containing three and two phenyldimethylsilyl)methyl ligands [5,6]. Now, following our investigations on the relationship between the steric volume of the substituents attached to the tin atom and the reactivity, as well as the stereoselectivity of the reactions of organotin hydrides, we considered it important to carry out the synthesis of (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl-5-methylcyclohexyl) methyltin hydride (9). This would enable us, in turn, to study the chemical properties of this new hydride that contains two bulky substituents: a (phenyldimethylsilyl)methyl group and a (−)-menthyl group attached to the tin atom.
2. Results and Discussion
The synthesis of the starting compounds needed for the study was carried out according to Scheme 1. (Chlorodimetilsilyl)methyl chloride (1) is commercially available.
(Phenyldimethylsilyl)methyl chloride (2) was obtained from compound 1 following known procedures [3]. In order to develop the best protocol to reach the tin hydrides, we first obtained ((phenyldimethylsilyl)methyl)trimethyltin 3. The alkylation of trimethyltin chloride with (phenyldimethylsilyl)methyl magnesium chloride in THF, using a ratio Grignard reagent/Me3SnCl = 1.1, afforded the new ((phenyldimethylsilyl)methyl)trimethyltin (3) in 72% yield. Similarly, the addition of (−)-menthyldimethyltin bromide (4) in ether to a solution of the same Grignard reagent in THF (ratio Grignard reagent/4 = 1.4) led to (((phenyldimethylsilyl)methyl) (1R,2R,5R)-2-isopropyl-5- methylcyclohexyl)dimethyltin (5) in 84% yield.
The reaction of 3 with bromine (Scheme 2) in methanol—ratio Br2/3 = 1.1—led to ((phenyldimethylsilyl)methyl)dimethyltin bromide (6) in 82% yield (Scheme 2). The reduction of bromide 6 with LiAlH4 in diethylether, under argon atmosphere, gave ((phenyldimethylsilyl) methyl) dimethyltin hydride (7) in 95% yield.
Selected values of 1H, 13C, and 119Sn-NMR data of the new organotins are included in Table 1.
Taking into account the previous results, we carried out a study on the halogenation of compound 5 (Scheme 3). The reaction of 5 with bromine in methanol using ratios Br2/5 = 1.1–2.2, led in all cases to mixtures of the corresponding mono- and dibromides.
On the other hand, the exchange reaction between 5 and HgBr2 in methanol using a ratio of HgBr2/5 = 1.5 gave exclusively (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl-5-methyl cyclohexyl)methyltin bromide (8) (Scheme 3) in 87% yield. The reduction of bromide 8 with LiAlH4 in dry diethylether under argon atmosphere, afforded (((phenyldimethylsilyl)methyl) (1R,2R,5R)-2- isopropyl-5-methylcyclohexyl)methyltin hydride (9) in 97% yield.
Selected values of 1H, 13C, and 119Sn-NMR data of the new organotins 5, 8, and 9 are included in Table 2.
These new organotin hydrides will be used in studies connected with the stereoselective reduction and hydrostannation of prochiral unsaturated systems.
Acknowledgments
CONICET and UNS of Argentina supported this work. A fellowship from CIC-PBA to VFT is gratefully acknowledged.
Conflicts of Interest
The authors declare no conflict of interest.
References
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Scheme 1.
Synthesis of starting compounds with Sn and Si atoms 3 and 5.
Scheme 2.
Synthesis of ((phenyldimethylsilyl)methyl) dimethyltin hydride (7).
Scheme 3.
Synthesis of (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl-5-methyl cyclohexyl) methyltin hydride (9).
Scheme 3.
Synthesis of (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl-5-methyl cyclohexyl) methyltin hydride (9).
Table 1.
Selected 1H-, 13C-, and 119Sn-NMR values of ((phenyldimethylsilyl)methyl)trimethyltin (3), ((phenyldimethylsilyl)methyl)dimethyltin bromide (6), and hydride 7 a.
Table 1.
Selected 1H-, 13C-, and 119Sn-NMR values of ((phenyldimethylsilyl)methyl)trimethyltin (3), ((phenyldimethylsilyl)methyl)dimethyltin bromide (6), and hydride 7 a.
 | |||
| Comp. 3 | Comp. 6 | Comp. 7 | |
| 13C-NMR | |||
| Me-Sn (1J) | −7.93 (334.0) | −0.01 (362.0) | −10.46 (347.8) |
| -CH2Sn (1J) | −5.30 (242.4) | 3.88 (257.7) | −7.32 (258.0) |
| Me-Si [3J(C-Sn)] | 0.28 (12.1) | −0.16 | −0.09 (14.1) |
| Ph-Si-CH2-Sn [3J(Ph-Sn)] | 141.72 (18.4) | 139.70 (20.1) | 141.10 (16.6) |
| 1H-NMR | |||
| Me-Sn [2J(Sn,H), Hz] | −0.02 (s, 2H, NO) | 0.57 (56.7) | −0.01 (s, 3H, 56.5); 0.00 (s, 3H, 56.5) |
| Me-Si | 0.57 (s, 6H) | 0.47 s, 6H) | 0.25 (s, 6H) |
| Sn-CH2 | 0.00 (s, 9H, 51,7) | 0.72 (s, 2H) | −0.12 & −0.11 (2s, 2H) |
| Sn-H [1J(Sn,H)] | -- | -- | 4.85 (m, 1H, 1739.5) |
| 119Sn-NMR | |||
| 9 | 135 | −96 [(1J(Sn,C) = 468)] [1J(Sn,H) = 1383] | |
a In CDCl3 (compounds 3 and 6) and C6D6 (7); chemical shifts in ppm; nJ(Sn,C) and nJ(Sn,H) coupling constants (in brackets) in Hz. Comp.: compound.
Table 2.
Selected 1H-, 13C-, and 119Sn-NMR values of (((phenyl dimethylsilyl)methyl)(1R,2R,5R)- 2-isopropyl-5-methylcyclohexyl)dimethyltin (5), (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl- 5-methylcyclohexyl)methyltin bromide (8), and hydride 9 a.
Table 2.
Selected 1H-, 13C-, and 119Sn-NMR values of (((phenyl dimethylsilyl)methyl)(1R,2R,5R)- 2-isopropyl-5-methylcyclohexyl)dimethyltin (5), (((phenyldimethylsilyl)methyl)(1R,2R,5R)-2-isopropyl- 5-methylcyclohexyl)methyltin bromide (8), and hydride 9 a.
 | |||
| Comp. 5 | Comp. 8 | Comp. 9 | |
| 13C-NMR | |||
| Me-Sn (1J) | −9.13 (297.5) −8.83 (298.2) | 2.58 (202.1) | −13.27 (NO) |
| −CH2Sn (1J) | −7.19 (210.1) | 1.95 (197.3) | −8.76 (NO) −8.36 (NO) |
| C-1-Sn (1J) | 32.60 (406.8) | 40.08 (426.4) 40.39 (427.0) | 32.61 (NO) |
| Me-Si [3J(C-Sn)] | −7.19 (2101) | −0.32 (18.7) −0.21 (NO) −0.17 (NO) −0.07 (NO) | −11.72 (NO) −11.58 (8.6) |
| Ph-Si-CH2-Sn [3J(Ph-Sn)] | 141.71 (15.9) | 140.31 (17.7) | 141.21 (14.8). |
| 1H-NMR | |||
| Compound 5 | −0.20–0.20 (m, 9H); 0.21–0.42 (m, 6H); 0.60–1.12 (m, 11H); 1.12–1.42 (m, 3h); 1.45–1.90 (m, 4H); 7.25–7.40 (m, 3H); 7.45–7.65 (m, 2H). | ||
| Compound 8 b | 0.32 (s, 6H, SiMe2); 0.42–0.48 (m, 2H); 0.49–0.56 (m,3H); 0.59–0.71 (m, 2H); 0.72–0.91 (m, 8H); 0.92–1.92 (m, 9H); 7.26–7.35 (m, 3H); 7.40–7.52 (m, 2H). | ||
| Compound 9 b | −0.27–0.16 (m, 9H); 0.24–0.39 (m, 6H); 0.65–1.08 (m, 9H); 1.12–1.42 (m, 3H); 1.44–1.95 (m, 3H); 4.91–5.01 [m, 1H, 1J(Sn,H) 1637 Hz]; 6.96–7.23 (m); 7.29–7.40 (m, 3H); 7.41–7.52 (m, 2H). | ||
| 119Sn-NMR | |||
| Comp. 5 Comp. 8 Comp. 9 | |||
| 0.79 | 132 | −214 [(1J(Sn,C) = 464)] [1J(Sn,H) = 1388] | |
a In CDCl3 (compounds 5 and 8) and C6D6 (9); chemical shifts in ppm; nJ(Sn,C) and nJ(Sn,H) coupling constants (in brackets) in Hz. b Mixture of diastereomers.
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Terraza, V.F.; Gerbino, D.C.; Podestá, J.C. Synthesis and Some Physical Properties of New Organometallic Compounds Containing Si and Sn Atoms. Proceedings 2019, 9, 62. https://doi.org/10.3390/ecsoc-22-05687
AMA Style
Terraza VF, Gerbino DC, Podestá JC. Synthesis and Some Physical Properties of New Organometallic Compounds Containing Si and Sn Atoms. Proceedings. 2019; 9(1):62. https://doi.org/10.3390/ecsoc-22-05687
Chicago/Turabian StyleTerraza, V. Fabricio, Darío C. Gerbino, and Julio C. Podestá. 2019. "Synthesis and Some Physical Properties of New Organometallic Compounds Containing Si and Sn Atoms" Proceedings 9, no. 1: 62. https://doi.org/10.3390/ecsoc-22-05687
