Silanes as reducing agents

An incomplete summary of silanes as reducing agents is provided in Table 4. 

Recent developments on iron catalysis have shown the enormous potential of this metal in the reduction of carbonyl groups with hydrogen or using transfer hydrogen and silanes as reducing agents [69]. However, the use of well-defined iron-NHC complexes as catalysts for these reduction processes is rather undeveloped [72]. 

Other important molecules that are useful intermediates in the synthesis of natural products are chiral diols. anli-l,2-Diols of type 30 were obtained in good yields (75-85%) and moderate to good diastereoselectivity (76-96% de) by a nickel-catalyzed three-component addition of a-silyloxy aldehydes 27, alkynyl silanes 28a, and reduction with triisopropyl silane (29a) (Scheme 11.11) [31]. The diastereoselectivity of this process could be explained by the Felkin model. Alternatively, a chiral alkynyl derivative can control the outcome of the reaction. Thus, the coupling of optically active, oxazolidinone-derived ynamides, aldehydes, and silane as reducing agent led to the formation of y-siloxyenamide derivatives with diastereoselectivities up to 99% [32]. 

---