Nysted reagent

Nysted reagent

Names
IUPAC name cyclo-Dibromodi-μ-methylene[μ-(tetrahydrofuran)]trizinc
Identifiers
CAS Number	41114-59-4
ChemSpider	21171210
Jmol interactive 3D	Image
InChI InChI=1S/C4H8O.2CH2.2BrH.3Zn/c1-2-4-5-3-1;;;;;;;/h1-4H2;2*1H2;2*1H;;;/q;;;;;;2*+1/p-2 Key: CCTHTLJWXPUNGT-UHFFFAOYSA-L InChI=1/C4H8O.2CH2.2BrH.3Zn/c1-2-4-5-3-1;;;;;;;/h1-4H2;2*1H2;2*1H;;;/q;;;;;;2*+1/p-2/rC4H8O.C2H4Br2Zn3/c1-2-4-5-3-1;3-6-1-5-2-7-4/h1-4H2;1-2H2 Key: CCTHTLJWXPUNGT-LIIURCMFAD
SMILES Br[Zn]C[Zn]C[Zn]Br.C1CCCO1
Properties
Chemical formula	C6H12Br2OZn3
Molar mass	456.14 g/mol
Hazards
Main hazards	Flammable, may form explosive peroxides and reacts violently with water
Safety data sheet	External MSDS
R-phrases	11-14-19-22-36/37/38
S-phrases	16-26-36
Flash point	−26.0 °C (−14.8 °F; 247.2 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

The Nysted reagent is a reagent used in organic synthesis for the methenylation of a carbonyl group. It was discovered in 1975 by Leonard N. Nysted in Chicago, Illinois. It was prepared by reacting dibromomethane and activated zinc in THF.^[1] The process is known as Nysted olefination. There is no confirmed mechanism but a proposed mechanism can be seen to bottom right.

A proposed mechanism for the Nysted olefination

A similar reagent is Tebbe's reagent.^[2] In the Nysted olefination, the Nysted reagent reacts with TiCl₄ to methylenate a carbonyl group. The biggest problem with these reagents are that the reactivity has not been well documented. It is believed that the TiCl₄ acts as a mediator in the reaction. Nysted reagent can methylenate different carbonyl groups in the presence of different mediators. For example, in the presence of BF₃•OEt₂, the reagent will methylenate aldehydes. On the other hand, in the presence of TiCl₄, TiCl₃ or TiCl₂ and BF₃•OEt₂, the reagent can methylenate ketones. Most commonly, it is used to methylenate ketones because of their general difficulty to methylenate due to crowding around the carbonyl group. Nysted is able to get into the tight space and methylenate the carbonyl group easily.

There is little research on Nysted reagent because of the hazards and high reactivity and the difficulty of keeping the reagent stable while it is in use. More specifically, it can form explosive peroxides when exposed to air and is extremely flammable. Also, it reacts violently with water. These make this reagent very dangerous to work with.^{[3]
[4][5][6][7]}

See also

• Petasis reagent
• Titanium-Zinc Methylenation
• Wittig reaction

References

1. Nysted, L.N. US Patent, 1975, 3 865 848. see Chem. Abstr., 1875, 83, 10406q.
2. "Nysted Reagent." Comprehensive Organic Name Reactions and Reagents. 2010; John Wiley and Sons, Inc.
3. Nysted Reagent. MSDS No.381985; Sigma-Aldrich; St. Louis, MO, April 3, 2009.
4. Furstner, A. (2003) J. Am. Chem. Soc. 125:15512. Amphidinolide
5. Paquette, L. A. (2004) J. Org. Chem. 69:2454.
6. Clark, J. S. (2004) Org. Lett. 6:1773.
7. Crich, D. (2006) J. Am. Chem. Soc. 128:8078.