Thiourea Catalysts for Carbonyl Hydrocyanation

Reference [4]). Chiral hydantoins could also be applied as catalysts for carbonyl hydrocyanation, but the enantiopurities were lower [5-7]. 

In 2005, thiourea catalyst 7 was proved to be an efHcient and recyclable catalyst for the cyanosilylation of various ketones 6 (Table 30.2) [8]. In the reaction with 5 mol% catalyst 7, TMSCN, and an alcoholic additive, aryl-alkyl (entries 1, 3-5), alkenyl-alkyl (entries 10, 11) ketones, and cyclic ketones (entry 12) afforded adducts in high yields (91-98%) and high enantiopurities (86-98% ee). Yields for heteroaromatic analogues were lower (81-88%) but with high enantioselectivities (97-98% ee) (entries 6, 7). The substrate scope could be also extended to aldehydes 

0 equiv. TMSCN, toluene, -78 °C R = aliphatic quant, yield 60-70%ee 

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