Surprising formylations with methylformamidopyridines and oxalyl chloride

4-N-(Methylformamido)pyridine with (COCl)2 gives the corresponding Vilsmeier reagent which reacts with 4-substituted dimethylanilines to produce 5-substituted-N-methylisatins. The corresponding 2-N-(methylformamido)pyridine under the same conditions generates benzo[2,3]pyrido[6,7-b][1,5]diazocines.