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The Hofmann–Martius rearrangement in organic chemistry is a rearrangement reaction converting an N-alkylated aniline to the corresponding ortho and / or para aryl-alkylated aniline. The reaction requires heat, and the catalyst is an acid like hydrochloric acid .
The Hofmann rearrangement (Hofmann degradation) is the organic reaction of a primary amide to a primary amine with one less carbon atom. [ 1 ] [ 2 ] [ 3 ] The reaction involves oxidation of the nitrogen followed by rearrangement of the carbonyl and nitrogen to give an isocyanate intermediate.
Example mechanism for alkyne zipper reaction. The 3-aminopropylamine anion attacks the same lesser-substituted carbon adjacent to the allene , removing a proton and catalyzing a similar process, where the electrons from the carbon-hydrogen bond move to form a triple-bond (an alkyne ).
The reaction mechanism is that of the related Hofmann degradation. [2] Weermann degradation 1st unsattuered. At first the carbonic acid amide (1) reacts with the sodium hypochlorite. After separate water and chloride an amine with a free bond is built 2. The intermediate (3) is generated by rearrangement. At this point two different mechanisms ...
The Dieckmann method is practical only for 5- to 8-membered rings (with modest yields for 7- and 8-membered). The Thorpe method is more easily modified via high dilution (e.g., 0.001 M in benzene/ether) to enable the synthesis of large rings, but 4-membered and 9- to 13-membered rings are still not accessible.
The rearrangement is widely used in organic synthesis. It is symmetry-allowed when it is suprafacial on all components. The transition state of the molecule passes through a boat or chair like transition state. An example of the Cope rearrangement is the expansion of a cyclobutane ring to a cycloocta-1,5-diene ring:
This organic reaction is closely related to the Hofmann elimination, but the base is a part of the leaving group. Sulfoxides can undergo an essentially identical reaction to produce sulfenic acids, which is important in the antioxidant chemistry of garlic and other alliums. Selenoxides likewise undergo selenoxide eliminations.
The usual way of doing this is from the relevant oxime, via the Neber rearrangement. [ 5 ] [ 6 ] The original Knorr synthesis employed two equivalents of ethyl acetoacetate , one of which was converted to ethyl 2-oximinoacetoacetate by dissolving it in glacial acetic acid , and slowly adding one equivalent of saturated aqueous sodium nitrite ...