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Polymer-Supported Hantzsch Ester as An Efficient Hydrogen Source
R. He, P. H. Toy*, Y. Lam*
National University of Singapore and the University of Hong Kong, P. R. of China
21 February 2008 (online)
The authors report an immobilization strategy for the Hantzsch ester as a heterogeneous hydrogen source. The direct microwave-assisted synthesis of the Hantzsch ester on pre-formed polymerous support 1 gave the active polymeric species 2. This polymer was a very efficient hydrogen source in different reactions, such as the reduction of α,β-unsaturated aldehydes 3 (yields up to 93%), the reductive amination of aldehydes 4 (yields up to 99%), and also the aromatization of DDQ 5 (99% yield). Surprisingly the reactions were very fast, also in comparison with homogeneously conducted transformations. The easy reaction workup, that the authors call ‘mix, filter and evaporate’ is alike highly remarkable.