Cookies disclaimer

I agree Our site saves small pieces of text information (cookies) on your device in order to deliver better content and for statistical purposes. You can disable the usage of cookies by changing the settings of your browser. By browsing our website without changing the browser settings you grant us permission to store that information on your device.

Knorr Pyrrole Synthesis

Fischer indole synthesis   Named Reactions in Organic Synthesis
Reaction category:
Heterocycle formation

Other featured reactions:

 

In 1886 L. Knorr heated a mixture of alpha-nitroso ethyl acetoacetate and ethyl acetoacetate together in glacial acetic acid in the presence of zinc dust to form a tetra-substituted pyrrole. Since then the condensation of an alpha-amino ketone or alpha-amino- beta ketoester with an active methylene compound is known as the Knorr pyrrole synthesis.

The Neber rearrangement can be used to prepare the precursor alpha-aminoketones from the corresponding oxime by reaction with tosyl chloride.

The alpha-aminoketones are often quite labile and can undergo self-condensation forming a pyrazine so they are often prepared by first nitrosating the ketone and then reducing it in situ.

An anti-inflammatory analgesic compound, 4,5,8,9-tetrahydro-8-methyl-9-oxothieno[3’3’:5,6]cyclohepta[1,2-b]-pyrrole-7-acetic acid was synthesized by H.E. Rosenberg and R.W. Ward utilizing the Knorr pyrrole synthesis.


Mechanism of the Knorr pyrrole synthesis:

mechanism of Knorr pyrrole synthesis



Which is your favorite named reaction?   Vote now


Find your reagents and pack sizes

 

Other reaction categories:

Electrophilic aromatic substitution

Nucleophilic substitution reactions

Transition Metal-Catalyzed Couplings

Oxidation

Reactions involving carbonyl compounds

Reduction reactions NEW!



Some relevant Alfa Aesar products for the Knorr pyrrole synthesis:
Ethyl acetoacetate, 99+%
Acetic acid, glacial, 99+%
Acetic acid, glacial, ACS, 99.7+%
Zinc powder, average 4-7 micron, 97.5% (metals basis)
Zinc powder, -100 mesh, 97+%
Zinc powder, -100 mesh, 99.9% (metals basis)
p-Toluenesulfonyl chloride, 98%
Sodium hydrosulfite, tech., 85+%

We have many ketone building blocks.

Chemicals

Life Science

Metals & Materials

Catalysts

Analytical & Labware