TANDEM WOLFF REARRANGEMENT TERT-AMINO-EFFECT SEQUENCE - SYNTHESIS OF 2-OXOINDOLLINIUM ENOLATE AND 1H-2-BENZOPYRANE DERIVATIVES

The thermal decomposition of dimethyl 1-diazo-2-oxo-(2-N,N-disubstituted aminophenyl)ethylphosphonates 1 gave rise to 2-oxoindolinium enolates 3 resulting from a Wolff rearrangement followed by an attack of the nitrogen atom on the intermediate ketene moiety. Ammonium ylides 5 resulting from the decomposition of 1 were also formed through a carbene path. The thermal decomposition of dimethyl 1-diazo-2-oxo-(2-(N,N-disubstituted aminomethyl)phenyl) ethylphosphonates 6 followed a different course and afforded 1H-2-benzopyranes 9 as the sole isolated products through a Wolff rearrangement - [1,5] H shift - ring closure sequence. The structures of 3a and 5a were confirmed by X-ray crystallography.