ADDITIONS OF ALKYLLANTHANUM TRIFLATES TO CARBONYL-COMPOUNDS - REACTIVE ORGANOMETALLIC NUCLEOPHILES

Addition of alkyl- or aryllithium compounds to lanthanum (III) triflate [La(OSO2CF3)3, 1] in ethereal solvents produces the title reagents 2 that undergo nucleophilic addition to carbonyl compounds under mild conditions. These reagents resemble alkylcerium halides in their reactions with enolizable carbonyl compounds but are more reactive. In particular, they are useful for the conversion of hindered, tertiary amides to ketones. 1H NMR spectroscopy was employed to clarify mechanistic aspects of this addition process. The title reagents actually appear to be a mixture of several species; formulation of their structure has proven elusive. However, in the presence of a tertiary amide, these species react to give a single, tetrahedral intermediate, which is quite stable in solution. © 1990, American Chemical Society. All rights reserved.