Regio‐, Diastereo‐, and Enantioselective Synthesis of Vicinal Diols via α‐Silyl Ketones

A new versatile and efficient regio‐, diastereo‐, and enantioselective synthesis of vicinal diols s‐ trans ‐ 4 , s‐ trans ‐ 5 , and s‐ cis ‐ 4 is described. Symmetrical ketones are converted into their SAMP‐or RAMP‐hydrazones which are then silylated with (isopropyloxy)dimethylsilyl chloride, followed by ozonolysis to afford the α‐silyl ketones ( R )‐ 2 of high enantiomeric purity (ee 90– ≥ 98%). On the other hand, methyl ketones, after conversion into the corresponding (−)–( S )‐1‐amino‐2‐(methoxymethyl) pyrrolidine (SAMP) hydrazones, are silylated and then alkylated with RI to afford unsymmetrical α‐silyl ketones ( S )‐ 3 of high enantiomeric purity (ee 90‐ ≥ 98%). The reduction of the above obtained α‐silyl ketones with L ‐ Selectride , followed by oxidative cleavage of the CSi bond gives rise to s‐ trans ‐4, s‐ trans ‐ 5 , and s‐ cis ‐ 4 with high diastereoselectivity (de 95‐ ≥ 98%) and without racemization (ee ≥ 90– ≥ 98%).