Over recent decades, intramolecular insertion reactions of metallocarbenes generated from α-diazo-β-ketocompounds into carbonhydrogen or heteroatomhydrogen bonds, have developed into an important method for the preparation of various carbocycles or heterocycles. 1 A Wolff rearrangement leading to a ketene can compete with the above processes. In the case of α-diazo-β-ketophosphonates this was first observed by Corbel et al. 2 and in the last few ...
