The Nysted reagent is a reagent used in organic synthesis for the

methylenation In organic chemistry, methylenation is a chemical reaction that inserts a methylene () group into a chemical compound: :\ce + \longrightarrow \ce\ce Typically, the reaction is used to prepare terminal alkenes from aldehydes and, less frequentl ...

of a

carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...

. It was discovered in 1975 by Leonard N. Nysted in Chicago, Illinois. It was originally prepared by reacting dibromomethane and activated zinc in THF. A proposed mechanism for the methenylation reaction runs as follows: Nysted Reaction

A similar reagent is

Tebbe's reagent Tebbe's reagent is the organometallic compound with the formula (C5H5)2TiCH2ClAl(CH3)2. It is used in the methylenation of carbonyl compounds, that is it converts organic compounds containing the R2C=O group into the related R2C=CH2 derivative. It ...

. 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. The Nysted reagent is able to overcome the additional steric hindrance found in ketones, and more easily methylenate the carbonyl group. In contrast to the

Wittig reaction The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Mos ...

the neutral reaction conditions of the Nysted reagent make it a useful alternative for the methylenation of easily enolizable ketones. 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.

References

{{DEFAULTSORT:Nysted Reagent Organozinc compounds Reagents for organic chemistry Zinc complexes

See also

References