Synthesis of substituted N-hydroxyureas via the in situ generation of t-butoxy isocyanate

Acyclic and Cyclic Ureas (Update 2013)

“…The tert-butyl group can then be cleaved under acidic conditions. [352] b-Oxo esters and tert-butyl N-[(4-nitrophenyl)sulfonyloxy]carbamate give imidazolidin-2-ones containing an N-tert-butoxy group upon treatment with calcium oxide in dichloromethane. [353] for references see p 301 18.8.22.16 N-Alkoxy-N-chloro-, N-Acyloxy-N-alkoxy-, and N,N-Dialkoxyureas 18.8.22.16.1 Synthesis of N-Alkoxy-N-chloro-, N-Acyloxy-N-alkoxy-, and N,N-Dialkoxyureas N-Alkoxy-N-chloroureas are relatively unstable compounds in pure form at 20 8 8C, but can be stored for a prolonged time at - 5 8 8C.…”

Different Reactivity of Hydroxylamine with Carbamoyl Azides and Carbamoyl Cyanides: Synthesis of Hydroxyureas and Carbamoyl Amidoximes

“…Alternatively, hydroxyamination can also be achieved by using benzyloxyamine to yield the corresponding N -benzyloxyurea, which can be subsequently reduced. , On the other hand, reaction of an amine with 4-nitrophenyl chloroformate and then with hydroxylamine also gives an N -hydroxyurea, albeit in a low yield of 30% for both reaction steps . More straightforward procedures, which give good results in specific cases, are based on the reaction of an amine with phenyl N -hydroxycarbamates, N -benzyloxycarbamates (in the latter case followed by reduction), or tert -butyl N -mesitylenesulfonoxycarbamate, followed by acid hydrolysis . Direct displacement of a benzotriazole group by hydroxylamine has also produced N -hydroxyureas, although the isolated yields range from extremely low to only moderate .…”