Simple Preparation of N-Substituted 4-Arylpyrrolones.

eernpounds,2) This prompted us to devise a general synthetic method for N-substituted 4-arylpyrrolones. rv-Unsubstituted 4-(4-chlorophenyl)pyrrolone has been prepared from 4-bromo-3-(4-chlorophenyl)-2-butenoic acid with a largc excess ammonia water,i) However, the application of this method, using excess arnines in an aqueous so[ution, would be Iimited, rv-Substitutcd arylpyrrelones may be prepared by traditional methods, i.e., exidation of 3-arylpyrroles, hydrolysis of 2-halopyrroles, and eyclization ef 7-fonmyl-fi-arylamides or 't/-amino-fi-hydroxy-B-ary]acides.i) Anothcr method by reacting allylsulfoxonium ylids with prirnary amincs has also been elaborated,4) Quite recently, an cMcient synthesis of N-benzylpyrrolenes by abnormal SN2 subst{tution of the amines towurd 2-chloro-3-butenoates has been reported.S) We present here a simple one-fiask preparation of N-substituted 4-arylpyrro]ones, staTting with 3-aryl-4-bromo-2-butcnoates and two equivalents of primary amines. 3-AryL-2-butenoates 1 were prepared by the Wittig-Horner reactien,E) the methyl group being brominated with NBS in fairly good yields. The transformution of2 to 3 proceeded smoothly by mixing the brornide with the individual primttry amine in benzenc, initially at room temperature for 5hr and then t'or2hr at 600C. The int.errnediate was tTeated in the next cyclization stcp witheut isolation. Thus, heating formed umine 3 ut