The thermolysis of 1-diazo-2-oxo-(2-N, N-disubstituted aminophenyl) ethylphosphonates 1 gave rise to 2-oxoindolinium enolate derivatives 4 through Wolff rearrangement and interaction of the tert-amino moiety with the ketene functionality. Variable amounts of either ammonium ylides 5 or of products resulting from their transformations were also formed during the course of the reaction. If the amino moiety was substituted by a benzyl or an ...