What Is the Bamford-Stevens Reaction?
Bamford-Stevens reaction is the process of converting p-toluenesulfonylhydrazone of ketone to olefin via diazo intermediate in the presence of strong base. Similar to the Shapiro reaction, this is a method for synthesizing olefins from ketones. The diazo intermediate can be isolated and can be used to prepare diazo compounds. Common bases include Na, NaOMe, LiH, NaH, NaNH2, alkyl lithiums and Grignard reagents. If an organolithium reagent (or Grignard reagent) is used as a base, it is a Shapiro reaction, which undergoes another reaction mechanism and the product is also an olefin.
Fig 1. The Bamford-Stevens reaction. [1]
Bamford-Stevens Reaction vs. Shapiro Reaction
Bamford-Stevens reaction mainly produces more substituted olefins and is a thermodynamic product. Shapiro reaction mainly produces less substituted olefins and is a kinetic product, using two equivalents of an organolithium compound (such as MeLi or BuLi) to react with benzenesulfonylhydrazone in ether, n-hexane, or tetramethylethylenediamine. The alkenyl lithium is generated in situ and then protonated to generate the olefin. The above method can generate olefins in high yields and without side reactions. Under this reaction condition, the tosylhydrazone of α,β-unsaturated ketones generates conjugated dienes. Alkenyl lithium may also react with other electrophilic reagents besides protons.
Mechanism of Bamford-Stevens Reaction
In protic solvent
Toluenesulfonylhydrazone and a strong base (such as sodium alkoxide) react in a protic solvent to form a diazo compound (which can be isolated in some cases). The diazo compound eliminates nitrogen and is converted to a carbocation, which can lose a proton to give an olefin or undergo a Wagner-Meerwein rearrangement. Therefore, the product may be a very complex mixture.
In aprotic solvent
When the reaction is carried out under aprotic conditions, the initially formed diazo compound loses a molecule of nitrogen to generate a carbene, which can then undergo a [1,2]-H migration or carbene insertion reaction.
In the Shapiro reaction
When the Shapiro reaction occurs, two equivalents of an organolithium reagent can remove the hydrogen on the nitrogen atom and the α-carbon position of the tosyl hydrazone, generating an olefin lithium intermediate through a carbon anion mechanism, which is then protonated to obtain an olefin.
Fig 2. Mechanism of Bamford-Stevens Reaction under different conditions. [1]
Application Examples of Bamford-Stevens Reaction
- Example 1: In the presence of a rhodium catalyst, Eschenmoser hydrazone can undergo a tandem Bamford-Stevens reaction-fat Claisen thermal rearrangement, and the intermediate is still a diazo compound and a 1,2-hydrogen migration product olefin ether [2].
- Example 2: Balram Singh et al. developed a synthetic strategy based on the Bamford-Stevens reaction, which can achieve the efficient synthesis of 1-phenyl-2-(β-D-glycopyranosyl)ethenes from native sugars. This method requires neither protection/deprotection of hydroxyl groups nor the use of any metals/metal ions [3].
Fig 3. Synthetic examples via Bamford-Stevens reaction.
Related Products
| CAS No. | Structure | Product | Inquiry |
| 15424-14-3 |  | Benzenecarbohydrazonoylchloride,N-phenyl- | Inquiry |
| 13587-16-1 |  | LITHIUM DEUTERIDE | Inquiry |
| 12125-45-0 | Sodium Azanide | Inquiry |
References
- Li, J.J. Name Reactions. Springer, Cham., Bamford-Stevens Reaction. 2021, pp 16-18.
- May, Jeremy A., et al. Journal of the American Chemical Society, 2002, 124(42), 12426-12427.
- Singh, Balram, et al. Synthetic Communications, 2019, 49(15), 1906-1912.
