Addition of Organometallic Nucleophiles to β-Keto Phosphonates

The reaction of some Grignard reagents with β-keto phosphonates results in nucleophilic addition to the carbonyl group to afford β-hydroxy phosphonates with extension of the carbon skeleton. Additions of allylmagnesium reagents have proven particularly efficient, especially in the presence of BF₃·OEt₂. Reactions of allylic zinc reagents with β-keto phosphonates also gave the desired β-hydroxy phosphonates, often in even better yields. With crotyl and prenyl organometallic reagents, the reactions proceed with allylic transposition. Because these allylation reactions expand the functionality of the original substrate, various transformations can be conducted on the initial products to provide convenient access to a variety of new phosphonates.