The Lewis acid mediated reaction of allyltributylstannane compounds with β-hydroxy-α-diazo carbonyls gives β-allyl-α-diazo carbonyl products in good yields. This reaction proceeds via a vinyl diazonium ion intermediate which is intercepted by the allylstannane nucleophile. Importantly, the diazo functional group is retained over the course of the reaction to give diazo-containing scaffolds with increased molecular complexity. Methallyltrimethylsilane also serves as a functional allyl transfer reagent in this reaction.