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

✍ Scribed by Dieter Enders; Shiro Nakai

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: German
• Weight: 258 KB
• Volume: 73
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19900730704

✦ Synopsis

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 (isopropy1oxy)dimethylsilyl chloride, followed by ozonolysis to afford the ci -silyl ketones (R)-2 of high enantiomeric purity (ee 90-2 98%). On the other hand, methyl ketones, after conversion into the corresponding (-)-(S)-l-amino-2-(methoxymethyl)pyrrolidine (SAMP) hydrazones, are silylated and then alkylated with RI to afford unsymmetrical ci -silyl ketones ( 9 3 of high enantiomeric purity (ee YO-2 98 %). The reduction of the above obtained c( -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 95-1 98%) and without racemization (ee 2 90-2 98 %).