Asymmetric Hydrogenation of Standard Test Substrates

3 Asymmetric Hydrogenation of Trisubstituted Alkenes 3.1 Asymmetric Hydrogenation of Standard Test Substrates 

While they have proven very selective for tiisubstituted olefins, they fail to produce high selectivity or reactivity with the substrate classes of tetrasubstituted olefins, terminal olefins, and 1,3-dienes. 

The catalyst derived from ligand 9 perform well with several classes of olefins albeit with slightly lower enantioselectivities in reduction of trisubstituted olefins, but are remarkably reactive toward 1,3-dienes [11,33]. Further examples of the size 

Reduction of all of the reported geminal diaryl substrates was completely under the control of the third stereo defining R-group. Particularly difficult were the sterically demanding 29 and the electron poor olefin 30, both of which required heating to produce poor to moderate yields. 

SimplePHOX 7a proved a useful tool to force the diastereomeric reduction of olefin 31a to pseudopteroxazole precursor 31b in perfect diastereoselectivity and 90% yield with only trace amounts of over-reduced product. NeoPHOX catalyst from ligand 14b, a closely related system to 7a, furnished product 32b in 93% ee, which was then easily recrystallized to enantiopure material with 58% recovery. The R enantiomer of 33b was synthesized by the use of catalyst from ligand 8a in 90% ee and 98% yield with the fully aromatized naphthalene as 2% byproduct. A higher catalyst loading of 2 mol% of catalyst from 7a was used to produce the 

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