The McFadyen–Stevens reaction is a chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 best described as a base-catalyzed thermal decomposition of acylsulfonylhydrazides to aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

s.
Dudman has developed an alternative hydrazide reagent.

Reaction mechanism

The mechanism of the McFadyen–Stevens reaction is still under investigation. Two groups have independently proposed a heterolytic fragmentation mechanism. The mechanism involves the deprotonation of the acyl sulfonamide followed by a 1,2-proton migration to give the alkoxide (3). The collapse of the alkoxide results in the fragmentation producing the desired aldehyde (4), nitrogen gas, and an aryl sulfinate ion (5).
Martin et al. have proposed a different mechanism involving an acyl

Acyl

An acyl group is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids.In organic chemistry, the acyl group is usually derived from a carboxylic acid . Therefore, it has the formula RCO-, where R represents an alkyl group that is...

 nitrene

Nitrene

In chemistry, a nitrene is the nitrogen analogue of a carbene. The nitrogen atom has only 6 valence electrons and is therefore considered an electrophile...

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