Organomolybdenum Complexes in Organic Synthesis- New methods for the Preparation of Cationic Diene Complexes and Applications to Synthesis

Abstract: Indolyl substituted pyranyl- and cyclohexenyl molybdenum complexes were synthesised through stereoselective nucleophilic addition of indoles to the corresponding cationic 2H-pyran or cyclohexadiene molybdenum complex. Decomplexation of an allylic molybdneum complex by treatment with iodine gave 1-(4-iodo-2-cyclohexenyl)-1H-indole-3-carbonitrile in high regio-selectivity. A new method for preparation of eta-4-diene molybdneum complexes was developed based on in situ generation of carbenium ions effectuating hydride abstraction from neutral eta-3-allylic substrates. The presence of 1,1,1,3,3,3-hexafluoroisopropanol as a co-solvent was critical for successful hydride abstraction to occur with various di-or triarylmethyl halides or carbinols as carbenium ion precursors. The first enantioselective hydride abstraction from an allylic molybdenum complex was performed, with an enantiomeric excess of up to 10%, utilising non-racemic 1-alkoxy-9-hydroxyxanthene derivatives as carbenium ion precursors.