Hydroxamic acid derivatives ureas

Rearrangement of O-acyl hydroxamic acid derivatives with base or heat to amines or urea derivatives (via isocyanates), or rearrangement of carboxylic acids via their hydroxamic acids to amines (see 1st edition). 

A partially purified enzyme from P. mirabilis (72) was found to have a molecular weight of 151,000. The urease of P. rettgeri is an inducible enzyme that appears only when urea, but not its analogs, are present in the media (73). Proteus vulgaris urease was found to be inhibited in vitro by thiourea and two derivatives (74), and by hydroxamic acids (93). 

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. ... 

Alternatively, the oxidation may occur by coupling to a suitable reactant. In 1997, Miyashita explored the scope of oxidative aroylations with nitrobenzene (Scheme ll.lO)." With the same oxidative reagent, nitrobenzene, benzoin reactions had already been developed back in 1982 using cyanide or thiamine. The combination of an aldehyde and nitrosobenzene, in the presence of an NHC, led to the formation of 7V-phenyl hydroxamic acids in good yields. These can be further converted into hydroxamic esters via a one pot reaction in the presence of a second (o,p-unsaturated) aldehyde. Furthermore, the oxidative coupling of aldehydes with carbodiimides in air allowed access to Af-acyl urea derivatives with IMes HCl 19 as the NHC precursor. Related thioesterifications reactions have also been reported using... 

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