General and regioselective synthesis of substituted pyrroles by metal-catalyzed or spontaneous cycloisomerization of (Z)-(2-en-4-ynyl)amines

A general and regioselective synthesis of substituted pyrroles 2 by cycloisomerization of readilyavailable (Z)-(2-en-4-ynyl)amines 1 is reported. Spontaneous cycloisomerization leading to 2 occurredin the course of preparation of enynamines bearing a terminal triple bond or a triple bond substitutedwith a phenyl or a CH2OTHP group. When the triple bond was substituted with an alkyl or alkenylgroup, enynamines were stable and could be converted into the corresponding pyrroles by metalcatalysis. CuCl2 was found to be an excellent catalyst for cycloisomerization of substrates substitutedat C-3, while PdX2 in conjunction with KX (X ) Cl, I) turned out to be a superior catalyst for thereaction of enynamines unsubstituted at C-3.