- A Fe3O4?SiO2/Schiff Base/Pd Complex as an Efficient Heterogeneous and Recyclable Nanocatalyst for One-Pot Domino Synthesis of Carbamates and Unsymmetrical Ureas
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A palladium-catalyzed domino method for the direct synthesis of carbamates and ureas has been developed by using readily available and economical starting materials (aryl halide, carbon monoxide, sodium azide, amines and alcohols) in a one-pot approach. The domino process underwent carbonylation, Curtius rearrangement, and nucleophilic addition. This protocol provides a step-economical and highly efficient reaction to access the wide range of valuable carbamates, symmetrical and unsymmetrical ureas with high yields under remarkable mild reaction conditions that are important factors in pharmaceutical science, biochemistry and agricultural industries. Furthermore, the magnetically recoverable nanocatalyst (Fe3O4?SiO2/Pd(II)) can be conveniently and swiftly recycled using external magnet and reused at least for seven times without noticeable loss of its catalytic activity.
- Inaloo, Iman Dindarloo,Majnooni, Sahar
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p. 6359 - 6368
(2019/11/05)
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- SYNTHESIS AND REACTIONS OF TRIPHENYLARSINIMINES
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Triphenylarsinimines formed in situ from isocyanates and triphenylarsine oxide have been found to react smoothly with carbonyl compounds like aldehydes, quinones and aromatic ketones giving the corresponding Schiff's bases in high yields.In the case of aldehydes, quinones or activated ketones, e.g., α-diketones, only a catalytic amount of triphenylarsine oxide is necessary for the reaction to proceed to completion.Quinones react with particular ease.Thus the previously unknown 9,10-phenanthrenequinone N-phenylimine 12 (R = Ph, Scheme IV) can be prepared in high yield from 9,10-phenanthrenequinone and phenyl isocyanate under catalytic influence of triphenylarsine oxide.Orthoquinones like 9,10-phenanthrenequinone react with vinylic isocyanates, forming monoimines 13 which rearrange to 1,4-oxazines 14 (Scheme V).Diisocyanates react under the catalytic action of triphenylarsine oxide with dialdehydes under mild conditions, forming some interesting new polymers 25, 26 in high yields.Reactions with aliphatic isocyanates give N-alkyl-N'-arylcarbodiimides, whereas reactions with isothiocyanates proceed through intermediates 20 and 21 to mixed carbodiimides 16, 24 and 25. Key words: Triphenylarsinimines; synthesis; reactions; Schiff's bases; unsymmetrical carbodiimides; polymers.
- Froeyen, Paul
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