Reactions of dicarbanion equivalents generated from complexation of 1,3-dienes on Ti(II) moiety

Conjugated dienes are able to react as 1,2- or 1,4-dicarbanions by coordination on Ti(II) moiety. These two possibilities are exemplified in this letter with isoprene, myrcene and several aldehydes to give 1,4- and 1,6-diols. When allowed to react with esters at room temperature, the titanium–diene complexes lead to cyclopentenol derivatives. Surprisingly, when this reaction is performed at lower temperature (−40 °C), allylic ketones are formed with high regio and diastereoselectivities.