A new and efficient one-pot synthesis of polysubstituted 2,5-dihydropyrrole derivatives by reaction between dialkyl acetylenedicarboxylates and b-aminoketones promoted by triphenylphosphine, is described. The prepared 2,5-dihydropyrroles can be easily oxidized to the corresponding pyrrole derivatives by chromium trioxide.The development of simple synthetic routes for widely used organic compounds from readily available reagents is one of the major tasks in organic synthesis. 1 2,5-Dihydropyrroles are important compounds which exhibit a wide range of biological activities and are useful intermediates in synthesizing natural products. Some 2,4-bisaryl-2,5-dihydropyrrole derivatives have been recently studied as novel, water-soluble KSP inhibitors. 2 2,5-Bisaryl-2,5-dihydropyrrole derivatives are part of an important class of photochromic compounds and often exhibit excellent photochromic properties, thermal and photochemical stability and very good fatigue resistance for photochemical reversibility. 3 In addition, their herbicidal, 4 pesticidal, 5 and anti-tumor 6 activities increasingly necessitate new research in order to simplify the synthesis of these materials. Despite their wide application range, available routes for the synthesis of 2,5-dihydropyrroles are limited. Previous syntheses of 2,5-dihydropyrroles utilized the Birch-reduction of electron-deficient pyrroles, 7 ring-closing metathesis (RCM) reactions, 8 1,3-dipolar cycloaddition of azomethine ylides to 2-(p-tolylsulfinile)acrylate, 9 and TiCl 4 /Zn promoted reductive cyclization of N,N-bis(2-aryl-2-oxoethyl)anilines. 3 Intramolecular Wittig reaction of the intermediates generated by the three-component addition reaction of activated acetylenes, triphenylphosphine and 2-amino carbonyl compounds has been recently used for the synthesis of five-membered nitrogen heterocycles. 10-12 In a continuation of our work on the reaction between trivalent phosphorus nucleophiles and electrondeficient acetylenic compounds in the presence of organic N-H acidic compounds, 13-15 here we wish to report an efficient, simple and one-pot synthetic method for some Nsubstituted 2,5-dihydropyrrole derivatives through the reaction of dialkyl acetylenedicarboxylates, a-arylaminoketones and triphenylphosphine.Thus, reaction between dimethyl acetylenedicarboxylate (2; DMAD), 1-(4-bromophenyl)-2-(4-methoxyphenylamino)ethanone (1a) and triphenylphosphine in dichloromethane at room temperature after 24 hours, afforded dimethyl 4-(4-bromophenyl)-1-(4-methoxyphenyl)-2,4-dihydro-1H-pyrrole-2,3-dicarboxylate (3a) in 90% yield. 16 Under similar conditions, different 2,5-dihydropyrrole derivatives were obtained using different derivatives of acetylene diesters and a-aminoketones (Table 1).The structures of compounds 3a-h were deduced from their elemental analyses and their IR, 1 H, and 13 C NMR spectra. The mass spectra of these 2,5-dihydropyrroles were fairly similar and displayed molecular ion peaks. The 500 MHz 1 H NMR spectrum of compound 3a exhibited three sharp signals at d = 3.70,...

Ninhydrin reacts with amides in ethanol to produce N- (2-hydroxy-1,3-dioxoindan-2-yl)amide derivatives in nearly quantitative yields. Reaction between these adducts and electron-deficient acetylenic esters in the presence of triphenylphosphine leads to dialkyl 8a-acetylamino-8-oxo-8,8a-dihydro-2H-1-oxacyclopenta[α]indene-2,3-dicarboxylate derivatives in good yields.

Pyrrole derivatives R 0120Efficient Synthesis of Functionalized 2,5-Dihydropyrrole Derivatives by Ph 3 P-Promoted Condensation Between Acetylene Esters and α-Arylamino Ketones. -The synthetically important dihydropyrroles can be easily oxidized to the corresponding pyrroles. -(ANARY-ABBASINEJAD*, M.; POORHASSAN, E.; HASSANABADI, A.; Synlett 2009 Synlett , 12, 1929 Synlett -1932 Dep. Chem., Islamic Azad Univ., Yazd, Iran; Eng.) -Mais 49-113