Total Synthesis of Murrayanine Involving 4,5‐Dimethyleneoxazolidin‐2‐ones and a Palladium(0)‐Catalyzed Diaryl Insertion

A new total synthesis of the natural carbazole murrayanine ( 1 ) was developed by using the 4,5‐dimethyleneoxazolidin‐2‐one 12 as starting material. The latter underwent a highly regioselective Diels–Alder cycloaddition with acrylaldehyde (=prop‐2‐enal; 13 ) to give adduct 14 ( Scheme 3 ). Conversion of this adduct into diarylamine derivative 9 was carried out via hydrolysis and methylation ( Scheme 4 ). Differing from our previous synthesis, in which such a diarylamine derivative was transformed into 1 by a Pd II ‐stoichiometric cyclization, this new approach comprised an improved cyclization through a more efficient Pd 0 ‐catalyzed intramolecular diaryl coupling which was applied to 9 , thus obtaining the natural carbazole 1 in a higher overall yield.