One-pot synthesis of 4-(alkylamino)-1-(arylsulfonyl)-3-benzoyl-1,5-dihydro-5-hydroxy-5-phenyl-2H-pyrrol-2-ones via a multicomponent reaction

An effective route to novel 4-(alkylamino)-1-(arylsulfonyl)-3-benzoyl-1,5-dihydro-5-hydroxy-5-phenyl-2H-pyrrol-2-ones 10 is described (Scheme 2). This involves the reaction of an enamine, derived from the addition of a primary amine 5 to 1,4-diphenylbut-2-yne-1,4-dione, with an arenesulfonyl isocyanate 7 Some of these pyrrolones 10 exhibit a dynamic NMR behavior in solution because of restricted rotation around the C-N bond resulting from conjugation of the side-chain N-atom with the adjacent alpha,beta-unsaturated ketone group, and two rotamers are in equilibrium with each other in solution (10 reversible arrow 11; Scheme 3). The structures of the highly functionalized compounds 10 were corroborated spectroscopically (IR, H-1- and C-13-NMR, and EI-MS), by elemental analyses, and, in the case of 10a, by X-ray crystallography. A plausible mechanism for the reaction is proposed (Scheme 4).