A New Synthesis of Push‐Pull Pyrroles, Their Oxidation to Stable 3 H ‐Pyrroles and an Unexpected Anellation Reaction

A new synthesis of push‐pull pyrroles of type 5 was developed starting from bis(imidoyl chlorides) 1 and various iminodiacetic acid derivatives 3 . The use of appropriate N ‐trifluoroacetyl residues as protecting/activating group proved to be the method of choice for the straightforward preparation of the 3,4‐diarylamino‐1 H ‐pyrroles 5 . When benzothiazole substructures are present in 2,5‐position of heterocycles 5 , a two‐electron oxidation leads to 3 H ‐pyrroles of type 6 in excellent yields. However, in the case of cyano or ester groups, a further oxidative process immediately led to the new 3 H ‐pyrrolo[3,4‐ b ]quinoxalines 7 via intramolecular ring anellation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)