Alonso, Miguel E. published the artcileEffect of catalyst on zwitterionic intermediacy in additions of dimethyl diazomalonate to vinyl ethers, Computed Properties of 14284-06-1, the publication is Tetrahedron (1989), 45(11), 3313-20, database is CAplus.
The reaction of di-Me diazomalonate with 2-alkoxy-6-methyl-3,4-dihydro-2H-pyran (I; R = H) in hot fluorobenzene was studied in the presence of some transition metal catalysts. The characteristic addition-elimination reaction that afforded the 3-malonyl-pyran derivative [I; R = CH(CO2Me)2] proceeded with the intervention of highly polar species, as indicated by the appearance of skeletal rearrangement products II that stem from the fragmentation of a carbenium ion at C-2 on the pyran ring. Mol. reorganization was strongly dependent on ligands and metal atom of the catalyst. This was the consequence of either a polar open-end transition state containing metal catalyst and dimethoxycarbonyl methylene sigma-bonded to C-3 of the pyran ring, or as a sigma olefin-metal carbene complex where stabilization of the pos. charge is provided by a strong polar interaction with high electron d. centers of appropriate ligands.
Tetrahedron published new progress about 14284-06-1. 14284-06-1 belongs to copper-catalyst, auxiliary class Copper, name is Copper(II) ethylacetoacetate, and the molecular formula is 0, Computed Properties of 14284-06-1.
Referemce:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4660968/,
Special Issue “Fundamentals and Applications of Copper-Based Catalysts”