New Methods for the Synthesis of 2-Arylpyrroles

Tvo short and efficient synthetic approaches for -mostly unknown-2-arylpyrroles are presented.The key intermediates 2 are conveniently obtained from cammercially available acetophenones 2 (method I) or benzoic acid derivatives 10, (method 11). 1 In connection with a synthetic program directed at psychoactive compounds ve needed a short, efficient synthesis for 2-phenylpyrroles 1, applicable for large scale preparations.Also a vide variety of substituents R and replacement of 2-phenyl by heteroaryl groups should be allowed.Only a few 2-phenylpyrrole syntheses.described in literature give rise to 3,4.5unsubstituted derivatives.nethods based on formation of the C2-N bond by cyclization reactions were described by everi in'^.^, using 1-phenylbut-2-en-Lone derivatives &, g , 3 and &.Similarly, chlorobutenanes g were described as precursors by Rosenmund .Other strategies are also based on intramolecular condensation reactions forming either the CZ-C3 4 bond (ringclosure of N-allylbenzamides) or the C3-C4 bond (treatment of acetophenone m i m e vinyl ethers vith strong base)5.Vittig6= and ~a e k i ~~ employed intermolecular C2-phenyl band connections using benzyne and phenyldiazonium salts, respectively.None of these methods met our criteria because of at least one of the following disadvantages: lack of general applicability, poor yields or drastic reaction conditions.