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

Article abstract of DOI:10.1002/hlca.19900730704

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 > 98percent).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 R1 to afford unsymmetrical α-silyl ketones (S)-3 of high enantiomeric purity (ee 90->98percent).The reduction of the above obtained α-silyl ketones with L-Selectride, followed by oxidative cleavage of the C-Si bond gives rise to s-trans-4, s-trans-5, and s-cis-4 with high diastereoselectivity (de 95->98percent) and without racemization (ee >90->98percent).