Lossen rearrangement degradation

Determination of pectic structures by specific degradation of pectins, via a carbodiimide 556 mediated Lossen rearrangement on alkaline hydrolysis of galacturonic acid residues 555, was reported (equation 248). 

Substituted imidazole-4,5-dicarbohydroxamic acids on Lossen rearrangement form 1-hydroxyxanthines. Thiazole-4,5-dicarbohydroxamic acids in their partial Lossen degradation, however, show little differentiation between the 4- and 5-position and hence mixtures of the [4,5-d] and the [5,4-d] structures (447) and (448) are formed. The isomer distribution appears to be affected by the solvent as well as by the sulfonyl chloride utilized in the reaction (68JHC331). 

Lossen rearrangement A modified version of the rearrangement for degradation of carboxylic acids is via reaction of the corresponding acid chloride RCOCl with l-BuOCONHOMs, and subsequent treatment with zinc triflate, 2,6-di-f-butylp)ridine, benzyl alcohol in MeCN. Benzyl carbamates RNHCOOBn are obtained. 

Lossen rearrangement. A modified version of the rearrangment for degradation of carboxylic acids is via reaction of the corresponding acid chlorides RCOCI with... 

This reaction is related to the Hofmann Degradation, Lossen Rearrangement, and Schmidt Reaction. 

This reaction was first reported by Lossen in 1872. It is a thermal or alkaline conversion of hydroxamic acid into an isocyanate via the intermediacy of its O-acyl, sulfonyl, or phosphoryl derivative. In the presence of water, amine, or alcohol, the isocyanate is converted into amine, urea or urethane, respectively. Therefore, this reaction is generally known as the Lossen rearrangement. Occasionally, it is also referred to as the Lossen reaction, Lossen degradation, or Lossen transformation. ... 

Degradation reactions of carboxylic acids and their derivatives to amines and their derivatives widi one less carbon unit involve reanangements of a carbon to an electron deficient nitrogen atom as key steps, namely the Hofmann Curtius (C), - Schmidt and Lossen rearrangements, as... 

Attempts to initiate formation of a nitrene, and its rearrangement to the iminooxo-phosphorane 80, by subjecting l-chloroamino-2,2,3,4,4-pentamethylphosphetane 1-oxide to a-elimination with sodium methoxide proved unsuccessful48). In contrast, however, the phosphorylhydroxylamides 88 rearrange in the presence of tert-butyl-amine to the heterocumulene 89 and then add base to give the phosphonic diamides 90 (>90%)49). The reaction is reminiscent of the well-known Lossen degradation. 

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