Amines, ureas from

According to the literature (6) the formation of urea from amine and isocyanate proceeds much faster than the formation of urethane or the hydrolysis of Isocyanate. 

The direct synthesis of ureas from amines with carbonyl derivatives is not always convenient because of the pressure equipment that is necessary. On the industrial production scale this is usually no problem. 

The synthesis of ureas from amines and C02 is a reversible process [125] which implies the elimination of water (Equation 6.16). 

The above methodologies, although being intrinsically valuable from a strictly synthetic point of view, are of poor interest in terms of their application. Clearly, the direct synthesis of ureas from amines and the heterocumulene (Equation 6.16), without the use of auxiliary reagents, has a greater practical significance. 

Scheme 5.13 KOH/PEG-catalyzed synthesis of symmetrical urea from amine and C02 [55]...

A recent addition to the field of functional, catalytic ionic liquids comes in the area of carbon dioxide fixation. However, in this example, the reaction was performed under solvent free conditions and the ionic liquid was just used as a catalyst. Using [Bmim][OH], yields of up to 58% were obtained for the synthesis of disubstituted ureas from amines and carbon dioxide.By considering the electrochemical reduction of carbon dioxide discussed above, it is clear that ionic liquids could have an important role to play in the area of carbon dioxide fixation. 

The historical S3mthesis of urea by heating potassium cyanate and ammonium sulfate is analogous to the synthesis of substituted ureas from amines and the cyanate ... 

N -Uric acid synthesis Amines from acylamines Ureas from amines... 

Ureas from amines and carbamyl chlorides NH —y NCONRa... 

Ureas from amines and cyanogen bromide NH NGONHg... 

Moreover, the synthesis of ureas from amines and CO2 involves the elimination of water. The use of some dehydrating agents, such as carbodiimides [746] and dio-rganophosphites [744], converts this method into a direct condensation, thus offering a new synthetic process that proceeds under mild conditions. 

Scheme 32. Synthesis of dialkyl urea from amine and CO2.

Scheme 33. A proposed mechanism for the synthesis of dialkyl urea from amine and CO2 catalyzed by [BMImjOH [107].

A rapid continuous process, not complicated by side reactions, has been reported for the prepn. of isocyanato- from amino-esters. The products can be used for attaching a lyophile group to water-insoluble compounds . A new synthesis of sym. ureas from amines and carbon monoxide has been reported . ... 

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