A domino 1,4-addition/alkyne carbozincation sequence based on a radical zinc-atom transfer process is disclosed. Two efficient multicomponent approaches to 3-alkylidenetetrahydrofurans from β-(propargyloxy)enoates bearing pendant alkynes (including ynamides) have been established: one involving the direct addition of dialkylzincs, and the second involving the dimethylzinc-mediated addition of alkyl iodides. Both sequences utilize the stereoselective formation of intermediate alkylidenezincs well suited for in situ functionalization with electrophiles.
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Chemla et al. (2011) studied this question.