Benzamide Hofmann rearrangement

In the mechanism outlined above, the Hofmann rearrangement is shown as intramolecular. How do we know that this is so To answer this question, T. J. Prosser and E. L. Eliel (of the University of Notre Dame) carried out degradation of a mixture of m-deuteriobenzamide and benzamide- N. When they analyzed the product with the mass spectrometer, they found only w-deuterioaniline and... 

A very mild procedure for the Hofmann rearrangement of aromatic and aliphatic carboxamides 409 is based on the use of (tosylimino)phenyl-X. -iodane, PhINTs, as the oxidant (Scheme 3.165) [506]. Owing to the mild reaction conditions, this method is particularly useful for the Hofmann rearrangement of substituted benzamides 409 (R = aryl), which usually afford complex reaction mixtures with other hypervalent iodine oxidants. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates 410, or their subsequent conversion into stable carbamates 411 by treatment with alcohols. Based on the previously reported mechanistic studies of the Hofmann rearrangement using other hypervalent iodine reagents [489,490,496], it is assumed that the reaction... 

Hofmann degradation of benzamide This reaction produces aniline, which contains one less carbon than the starting material (benzamide). The group (phenyl) attached to the carbonyl carbon in the amide (benzamide) is found joined to nitrogen in the product (aniline). This is an example of molecular rearrangement. 

Preparation from Nitrene Intermediates. A convenient, small-scale method for the conversion of carboxylic acid derivatives into isocyanates involves electron sextet rearrangements, such as the ones described by Hofmann and Curtius (12). For example, treatment of benzamide [55-21 -0] with halogens leads to an AJ-haloamide (2) which, in the presence of base, forms a nitrene intermediate (3). The nitrene intermediate undeigoes rapid rearrangement to yield an isocyanate. Ureas can also be formed in the process if water is present (18,19). 

CXVIII, which will form lactams and are therefore cis to each other.756 As in the other molecular rearrangements, the migrating group never leaves the vicinity of the atoms which are concerned. Thus when a Hofmann reaction is carried out with (+) 3,5-dinitro-2-[a-naphthyl]-benzamide (CXIX) (which owes its optical activity to the restricted rotation of the bond connecting the benzene and naphthalene nuclei) an optically active amine (CXX) is formed 76 which has the same configuration as the starting material.77... 

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