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, Bu<sub>2</sub>SnIH−Lewis base (Lewis bases; HMPA or tripiperidinophosphine oxide) (type A), Bu<sub>2</sub>SnFH−HMPA (type B), and Bu<sub>3</sub>SnH−Bu<sub>4</sub>NX (X = F, CN) (type C), were characterized as nucleophilic, chelation, and nonchelation types of reductants, respectively, in the reaction with 2,3-epoxy ketones <b>1</b>. These reagents, which promoted a reduction of the epoxy ring and <i>syn</i>-selective and <i>anti</i>-selective carbonyl reduction, respectively, were spectroscopically confirmed with <sup>1</sup>H, <sup>13</sup>C, <sup>19</sup>F, and <sup>119</sup>Sn NMR and FT-IR. Furthermore, the correlations between their structures and selective reducing abilities were discussed.