Keck allylation

The first total synthesis of (+)-stenine has been accomplished in the laboratory of D.J. Hart/ The key steps were an intramolecular DIels-Alder reaction, an amidine variant of the Curtius rearrangement, an Eschenmoser-Clalsen rearrangement, a halolactonization, and a Keck allylation. The allylic alcohol precursor and A/,A/-dimethylacetamide dimethyl acetal was heated to reflux in xylenes for 4h to afford the desired amide in 93% isolated yield. The transition state most likely adopted a boatlike conformation. 

The spongistatins are a family of architecturally complex bisspiroketal macrolides, which display extraordinary cytotoxicity. During the second generation synthesis of the ABCD subunit of spongistatin 1, A.B. Smith and coworkers utilized the Keck allylation to construct the Kishi epoxide. The allylation was carried out under standard conditions, using tributyl-(2-ethylallyl)-stannane as the allylstannane reactant. The desired product was formed in high yield and a diastereomeric ratio greater than 10 1. 

Demonstrated here is the mechanism of the Keck allylation proceeding via a radical pathway. 

Other references related to the Keck allylation are cited in the literature. 

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