S y n t h e s i s o f N -S u b s t i t u t e d P y r r o l e s i n W a t e rAbstract: An operationally simple, practical, and economical protocol for iron(III) chloride catalyzed Paal-Knorr pyrrole synthesis in water in good to excellent yields has been developed. Several Nsubstituted pyrroles are readily prepared from the reaction of 2,5-dimethoxytetrahydrofuran and aryl/alkyl, sulfonyl and acyl amines under very mild reaction conditions

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The versatility of palladium(II) acetate and palladium on activated charcoal catalysts with triethylsilane has been investigated in the hydrogenation and the isomerization of carbon-carbon double bond of 1-alkenes. The reduction of 1-alkenes was carried out in the presence of triethylsilane, ethanol and a catalytic amount of palladium(II) acetate or palladium on activated charcoal, at room temperature. This facile and efficient method affords high yields for hydrogenation of unsaturated alkenes to the corresponding alkanes. Then the carbon-carbon double bond isomerization of 1-alkenes was tested using the same catalysts in the absence of solvent. The system palladium(II) acetate-triethylsilane was found to be more effective compared with palladium on an activated charcoal-triethylsilane system at room temperature, while comparable results were obtained at 50 • C for both catalysts.

The efficient and very simple conjugate addition of aromatic and aliphatic amines to a,b-unsaturated carbonyl compounds under solvent-free conditions in the presence of catalytic amount of silicon tetrachloride is reported. The reaction of aryl and alkyl amines with different Michael acceptors gave the corresponding Michael adducts with simple catalyst and good to excellent yields.The aza-Michael addition reaction is one of the most important methodologies in synthetic organic chemistry for preparation of b-aminocarbonyl compounds, which not only constitute components of biologically important natural products but also serve as key intermediates for the synthesis of b-amino alcohols, antibiotics, b-amino acids, chiral auxiliaries, and other nitrogen-containing compounds. 1,2The Mannich reaction is a classical method for the synthesis of b-amino carbonyl compounds. However, the reaction has disadvantages such as harsh reaction conditions, long reaction times, and a relatively narrow scope of substrates. 3 The aza-Michael addition of nitrogen nucleophiles including amides, carbamates, sulfonamides, and amines to electron-deficient alkenes in the presence of strong base or acid catalyst has attracted considerable attention as an alternative route for the synthesis of b-amino carbonyl compounds. 4 Since some functional groups may be susceptible to strong acid or base, a variety of catalysts 5 and promoters for aliphatic amines 6 have been introduced over the past few years.However, there are still some limitations with the existing methods; for example, the range of amine nucleophiles and Michael acceptors well suited to both catalytic and stoichiometric methodologies is generally restricted to simple aliphatic amines and Michael acceptors and there have been few reports involving simple catalysts or reagents to effect these transformations. 7 Thus, development of an efficient catalytic protocol that could overcome the above-mentioned disadvantages and facilitate the addition of both aromatic/aliphatic amines to a,bunsaturated compounds remains a challenge.As a part of our research aimed at developing green chemistry by using water as the reaction medium or by performing organic transformations under solvent-free conditions, 8 we describe herein a simple, highly efficient, and eco-friendly method for the synthesis of b-amino carbonyl compounds from aromatic and aliphatic amines and a,b-unsaturated Michael acceptors under solvent-free conditions.In order to find the best reaction conditions, we first studied the reaction of aniline and methyl acrylate with different loadings of starting materials and catalyst. It was found that the reaction of methyl acrylate (1.04 equiv) and aniline (1 equiv) in the presence of commercially available silicon tetrachloride (2 mol%) under solvent-free conditions proceeded smoothly within four hours to afford the conjugate addition product exclusively and in quantitative yield. Furthermore, in organic solvents, such as CH 2 Cl 2 , MeCN, toluene, ethanol, water, and tetrahydrofuran the M...

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