Nierenstein reaction

Reaction mechanism

The reaction proceeds through a diazonium salt intermediate formed when diazomethyl anion displaces the chloride:

Excess diazomethane can act as a base, abstracting a hydrogen from the diazonium intermediate. The results are a neutral diazoketone, which does not react further; and methyldiazonium chloride, which decomposes to chloromethane. The unreactive diazoketone can, however, be re-activated with hydrogen chloride to give the Nierenstein product:

In even some cases with limited diazomethane, the reaction process can stall into the diazoketone pathway, requiring reparative HCl gas. Substitution of a mixed anhydride for the acyl halide also gives the diazoketone.

Examples

Nierenstein's original 1924 publication:{{cite journal

A reaction from benzoyl bromide going haywire and forming the dioxane dimer:{{cite journal

References

References

1. McPhee, W. D; Klingsberg, E. ''[[Organic Syntheses]]'', Coll. Vol. 3, p.119 (1955); Vol. 26, p.13 (1946). ([https://orgsyn.org/demo.aspx?prep=cv3p0119 Article])
2. Taber, Douglass. (3 July 2017). "The Zhai synthesis of (+)-harringtonolide". Organic Chemistry Highlights.