Reactions of alkyllithium and grignard reagents with (cyclopentadienyl)dicarbonyl(2-methylbutadiene)molybdenum: Observations of solvent effects on regioselectivity

Article abstract of DOI:10.1021/om00019a001

The regioselectivity that is observed during reactions of the title complex with hydride and carbon nucleophiles was found to be solvent-dependent. In diethyl ether solution, alkyllithiums and Grignard reagents add preferentially to C-1, while in THF and other solvents C-4 addition dominates. Inclusion of complexing agents (TMEDA or HMPA) in the reactions in ether leads to a reversal of selectivity. All hydride nucleophiles add selectively at C-1, irrespective of solvent. Decomplexation of the C-1 adducts, with concomitant addition of a second nucleophile, allows the completely stereoselective construction of trisubstituted carbon-carbon double bonds. The first example of osmylation of an alkene substituent in the presence of a π-allyl-Mo-(CO)₂Cp group is described.