The Bamford–Stevens reaction refers to the base-catalyzed decomposition of tosylhydrazones derived from aldehydes or ketones to generate alkenes. This reaction was first reported in 1952 by British chemist William Randall Bamford and Scottish chemist Thomas Stevens Stevens, and is named after them. When carried out in aprotic solvents, the reaction predominantly yields Z-alkenes, whereas in protic solvents, it gives a mixture of E- and Z-alkenes. As an efficient method for converting aldehydes and ketones into alkenes, the Bamford–Stevens reaction has found wide application in synthetic methodology and the synthesis of complex molecules.

Reagents: Base
Reactants: Aldehydes, ketones, tosylhydrazine
Products: Alkenes
Reaction Type: Elimination reaction

Experimental Tips:

• Common bases used in the Bamford–Stevens reaction include Na, NaOMe, LiH, NaH, and NaNH₂.

• When organolithium reagents or Grignard reagents are used as the base, the reaction is referred to as the Shapiro reaction.

• The Bamford–Stevens reaction generally gives more substituted alkenes (thermodynamic products), whereas the Shapiro reaction tends to produce less substituted alkenes (kinetic products).

• Aldehydes and ketones react with tosylhydrazine under acidic conditions to form the corresponding tosylhydrazones.

Reaction Mechanism:

1. The first step of the reaction involves the formation of a diazo compound

2. In protic solvents, the diazo compound decomposes to form a carbocation.

3. In aprotic solvents, the diazo compound decomposes to form a carbene.

Original Reference:
Bamford, W. R.; Stevens, T. S. Journal of the Chemical Society, 1952, 4735–4740.

Popular Citations:

• Stoichiometric Photochemical Carbene Transfer by Bamford–Stevens Reaction. Chemistry Europe, 2020, 26(12), 2586–2591.

• Non-Carbonyl-Stabilized Metallocarbenoids in Synthesis: The Development of a Tandem Rhodium-Catalyzed Bamford−Stevens/Thermal Aliphatic Claisen Rearrangement Sequence. J. Am. Chem. Soc., 2002, 124(42), 12426–12427.