Ketalised 3,4-dihydroxybutyllithiums: New intermediates to transfer four-carbon diol functionality to electrophilic reagents

The reaction of ketalised 1-chlorobutane-3,4-diol la,b with lithium powder and a catalytic amount of 4,4'-di-tert-butylbiphenyl (DTBB, 4 mol %) in the presence of an electrophile [(PrCHO)-C-i, Bu(t)CHO, PhCHO, P(n)COMe, (CH2)(5)Co] at -78 degrees C in THF (Method A: Barbier-type conditions) leads, after hydrolysis, to the formation of the corresponding ketalised reaction products 2aa-bf. Alternatively, the reaction can be carried out in a two-step process (Method B), which implies first a DTBB-catalysed lithiation folowed by reaction with an electrophile [Me(3)SiCl, (PrCHO)-C-i, Bu(t)CHO, PhCHO, Me(2)CO, Et(2)CO,Pr(n)COMe, (CH2)(5)CO, PhCOMe] both steps being performed at -78 degrees C. When the starting materials are chiral, this methodology allows the preparation of chiral protected di or triols in a non-diastereoselective manner. Copyright (C) 1996 Elsevier Science Ltd