Metal on a Chiral Support

This is the earliest strategy for preparing a chiral solid hydrogenation-dehydrogenation catalyst (for reviews see [l-3,5,7,8]). Quartz, silk fibroin, cyclodextrin, and cellulose were applied as chiral supports of natural origin. With a Pd/silk catalyst up to 66 % optical yield was obtained in C=C bond hydrogenation, but subsequently the results proved irreproducible. 

A drawback of this approach is that the chiral support can provide the necessary chiral environment only for the neighboring metal atoms (metal-support interface). Note that the chiral environment induced by a chiral support is much more rigid than that created by an adsorbed soluble chiral modifier (see below). The stability 

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