Thioureas dissymmetrical

Chiral amines and diamines are readily available substrates for the synthesis of ligands for transition metal-catalysed reactions since they can easily be transformed into chiral ureas and thioureas. Therefore, several groups have prepared chiral symmetrical ureas and thioureas, dissymmetrical ureas and thioureas, amino-urea and thiourea derivatives. Finally polyureas and non-soluble polythioureas were also prepared and tested as ligands for asymmetric catalysis. 

A recent paper from Katritsky summarises all the preparations of achiral dissymmetrical thioureas and proposes a new one, based on l-(alkyl/arylthio-carbamoyl)benzotriazoles, which act as masked isothiocyanates. As described in the previous section, other N-heterocyclic derivatives can be used instead... 

New catalysts were prepared after optimisation of the Ugand structure. The most efficient organo catalyst for this reaction was an amido-thiourea derivative (Scheme 43). Interestingly, dissymmetrical ligands were more efficient and selective for this reaction. 

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See also in sourсe #XX -- [ , ]

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