I was trying to make diazaindoles from diaminobromopyrimidines by Pd-catalyzed arylation of a cyclic 1,3-diketone (dimedone) when I met these cyclized strangers:
Apparently the cyclization product resulted from a reductive Heck coupling with a condensation product of acetaldehyde plus dimedone. I used a fairly high Pd(II) pre-catalyst loading (10 mol%) so I guess the acetaldehyde equivalent was generated by the Pd(II)-promoted oxidation of triethylamine.
In this wild story the addition product does not beta-eliminate Pd(0) – as in typical Heck reaction – but undergoes a protonolysis instead. Pd(II) re-emerges from the sequence at the end, ready to hunt down and oxidize another molecule of triethylamine. (Credits: Dr. Ni for ROESY)