NMR Studies of Three Types of Highly Coordinated Organotin Hydrides:  Chemo-, Regio-, and Stereoselective Reduction of 2,3-Epoxy Ketones

Three types of highly coordinated organotin hydrides, Bu₂SnIH−Lewis base (Lewis bases; HMPA or tripiperidinophosphine oxide) (type A), Bu₂SnFH−HMPA (type B), and Bu₃SnH−Bu₄NX (X = F, CN) (type C), were characterized as nucleophilic, chelation, and nonchelation types of reductants, respectively, in the reaction with 2,3-epoxy ketones 1. These reagents, which promoted a reduction of the epoxy ring and syn-selective and anti-selective carbonyl reduction, respectively, were spectroscopically confirmed with ¹H, ¹³C, ¹⁹F, and ¹¹⁹Sn NMR and FT-IR. Furthermore, the correlations between their structures and selective reducing abilities were discussed.