Isopropylmagnesium chloride
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.012.680 |
| EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C3H7ClMg | |
| Molar mass | 102.84 g·mol−1 |
| Solubility | Ethyl ether |
| Hazards | |
| GHS labelling: | |
 
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| Danger | |
| H225, H260, H314 | |
| P210, P223, P231+P232, P233, P240, P241, P242, P243, P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P335+P334, P363, P370+P378, P402+P404, P403+P235, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Isopropylmagnesium chloride is an organometallic compound with the general formula (CH3)2HCMgCl. This highly flammable, colorless, and moisture sensitive material is the Grignard reagent derived from isopropyl chloride. It is commercially available, usually as a solution in tetrahydrofuran.
Synthesis and reactivity
[edit]Solutions of isopropylmagnesium chloride by treating isopropyl chloride with magnesium metal in refluxing ether:[1]
- (CH3)2HCCl + Mg → (CH3)2HCMgCl
This reagent is used to prepare other Grignard reagents by transmetalation.[2] An illustrative reaction involves the generation of the Grignard reagent derived from bromo-3,5-bis(trifluoromethyl)benzene:[3]
- (CH3)2HCMgCl + (CF3)2C6H3Br → (CH3)2HCCl + (CF3)2C6H3MgBr
Addition of one equivalent of LiCl to isopropylmagnesium chloride gives "Turbo Grignard" solutions, named so due to the increased rate and efficiency for transmetalation reactions.[4][5]
Isopropylmagnesium chloride is also used to prepare isopropyl compounds, such as chlorodiisopropylphosphine:[6]
- PCl3 + 2 (CH3)2CHMgCl → [(CH3)2CH]2PCl + 2 MgCl2
This reaction exploits the bulky nature of the isopropyl substituent.
Turbo-Grignard reagents
[edit]As initially reported by Knochel et al.,[7] lithium chloride, isopropylmagnesium chloride enhances the ability of isopropylmagnesium chloride toward transmetalation reactions. The more reactive species, a LiCl-iPrMgCl complex, is called a Turbo-Grignard reagent. These species are related to Turbo-Hauser bases, a family of magnesium amido compounds containing also LiCl.[8] "Turbo-Grignards", as they are often called, are aggregates with the formula [i-PrMgCl·LiCl]2. These species promote formation of aryl and heteroaryl Grignard reagents by halogen-magnesium exchange:[9]
- fast, homogeneous: XC6H4Br + i−PrMgCl·LiCl → XC6H4MgCl·LiCl + i−PrCl + MgBrCl
The traditional method for generating the aryl Grignard reagent proceeds less predictably:
- slow, heterogeneous: XC6H4Br + Mg → XC6H4MgBr
Furthermore, traditional routes to Grignard reagents has limited functional group compatibility, whereas the Turbo-Grignard method tolerates other halides, some ester groups, and nitriles.
References
[edit]- ^ Seyferth, Dietmar (2009-03-23). "The Grignard Reagents". Organometallics. 28 (6): 1598–1605. doi:10.1021/om900088z. ISSN 0276-7333.
- ^ Knochel, P.; Dohle, W.; Gommermann, N.; Kneisel, F. F.; Kopp, F.; Korn, T.; Sapountzis, I.; Vu, V. A. (2003). "Highly Functionalized Organomagnesium Reagents Prepared through Halogen–Metal Exchange". Angewandte Chemie International Edition. 42 (36): 4302–4320. doi:10.1002/anie.200300579. PMID 14502700.
- ^ Johnnie L. Leazer Jr; Raymond Cvetovich (2005). "A Practical and Safe Preparation of 3,5-Bis(trifluoromethyl)acetophenone". Org. Synth. 82: 115. doi:10.15227/orgsyn.082.0115.
- ^ Krasovskiy, Arkady; Knochel, Paul (2004-06-21). "A LiCl‐Mediated Br/Mg Exchange Reaction for the Preparation of Functionalized Aryl‐ and Heteroarylmagnesium Compounds from Organic Bromides". Angewandte Chemie International Edition. 43 (25): 3333–3336. doi:10.1002/anie.200454084. ISSN 1433-7851.
- ^ Hermann, Andreas; Seymen, Rana; Brieger, Lukas; Kleinheider, Johannes; Grabe, Bastian; Hiller, Wolf; Strohmann, Carsten (2023-06-19). "Comprehensive Study of the Enhanced Reactivity of Turbo‐Grignard Reagents**". Angewandte Chemie International Edition. 62 (25). doi:10.1002/anie.202302489. ISSN 1433-7851.
- ^ W. Voskuil; J. F. Arens (1968). "Chlorodiisopropylphosphine". Org. Synth. 48: 47. doi:10.15227/orgsyn.048.0047.
- ^ Krasovskiy, A.; Knochel, P. (2004). "A LiCl-Mediated Br/Mg Exchange Reaction for the Preparation of Functionalized Aryl- and Heteroarylmagnesium Compounds from Organic Bromides". Angew. Chem. Int. Ed. 43 (25): 3333–3336. doi:10.1002/anie.200454084. PMID 15213967.
- ^ Li-Yuan Bao, Robert; Zhao, Rong; Shi, Lei (2015). "Progress and Developments in the turbo Grignard Reagent i-PrMgCl·LiCl: A Ten-Year Journey". Chemical Communications. 51 (32): 6884–6900. doi:10.1039/c4cc10194d. PMID 25714498.
- ^ Knochel, Paul; Gavryushin, Andrei (2010). "Lithium Dichloro(1-methylethyl)-magnesate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01161. ISBN 978-0-471-93623-7.