Synthesis and carbon-carbon bond-forming reactions of tungsten, molybdenum, and rhenium enolates

Abstract

Alkylation of sodium cyclopentadienyl(tricarbonyl) metaliates of tungsten and molybdenum with α-chloro ketones and α-chloro esters gives stable tungsten and molybdenum enolates (23a-23d)• Similar alkylation of sodium pentacarbonylrhenate provides rhenium enolates 24. Compounds 23 lose carbon monoxide and rearrange to η3 -oxaallyl complexes 25 upon irradiation. Compounds 25 react with benzaldehyde to give transition metal aldolates (26), which may be converted into the silylated aldol (27) and the corresponding metal chloride (28) upon reaction with trimethylsilyl chloride. Rhenium enolate 27 undergoes thermal aldol reaction with benzaldehyde and suffers exchange of one carbonyl ligand upon being heated with triphenylphos-phine. The resulting cis monophosphine complex (30) and compound 27 itself both react with triphenylphosphine in refluxing acetenitrile to give complex 31, in which the enolate moiety has been transferred from rhenium to the nitrile function. Several schemes for establishing catalytic cycles based on the foregoing reactions are suggested. © 1985 IUPAC