No abstract

No abstract

No abstract

Alkyl isocyanides undergo a smooth reaction with isopropylidene Meldrum's acid in the presence of pyrrole or indole to produce 1-alkyl-3,3-dimethyl-4-(1H-pyrrole-2-carbonyl)-pyrrolidine-2,5-diones or 1-alkyl-4-(1H-indole-3-carbonyl)-3,3-dimethylpyrrolidine-2,5-diones in good yields.As part of our current studies on the investigation of the reaction between isopropylidene Meldrum's acid and alkyl isocyanides 1-3 in the presence of proton sources, we wish to report a simple one-pot reaction between alkyl isocyanides and isopropylidene Meldrum's acid in the presence of pyrrole or indole. This three-component reaction leads to highly functionalized 4-(1H-pyrrole-2-carbonyl)-pyrrolidine-2,5-dione or 4-(1H-indole-3-carbonyl)-pyrrolidine-2,5-dione derivatives in good yields.The reaction of alkyl isocyanides 1 with isopropylidene Meldrum's acid 2 in the presence of pyrrole 3 or indole 8 in CH 2 Cl 2 at room temperature leads to 1-alkyl-3,3-dimethyl-4-(1H-pyrrole-2-carbonyl)-pyrrolidine-2,5-diones 4 or 1-alkyl-4-(1H-indole-3-carbonyl)-3,3-dimethyl-pyrrolidine-2,5-diones 9. The reaction of 1 with 2 in the presence of pyrrole proceeded at room temperature in CH 2 Cl 2 and was complete within 24 hours. The 1 H NMR and 13 C NMR spectra of the crude products clearly showed the formation of 4 (see Scheme 1). Scheme 1The structures of compounds 4a-c were deduced from their elemental analyses and IR, 1 H, and 13 C NMR spectra. The mass spectra of these products displayed molecular ion peaks at appropriate m/z values. The IR, 1 H NMR, and 13 C NMR data for compounds 4a-c are given in the experimental section.The IR spectrum of 4a clearly exhibits NH stretching band at 3265 cm -1 . The 1 H NMR spectrum of 4a exhibits four sharp singlets arising from CMe 2 (d = 1.10 and 1.39 ppm), CMe 3 (d = 1.60 ppm) and CH (d = 4.06 ppm) protons. Three multiplet signals at d = 6.30, 6.91 and 7.10 ppm are observed for the C-H protons of the pyrrole residue, together with a signal at d = 10.25 ppm for the NH proton. The 13 C NMR spectrum of 4a shows thirteen distinct resonances in agreement with the proposed structure.The plausible way of formation of the product is proposed in Scheme 2. The reaction starts from [4+1] cycloaddition of the isocyanide to the electron-defficient heterodiene moiety of isopropylidene Meldrum's acid to form intermediate iminolactone 5. 4-6 This intermediate first loses acetone to give acyl ketene 6 which then reacts with pyrrole at the ketene carbonyl to form the second acyl ketene 7. Ring closure of this ketene leads to the product 4a. Scheme 2Similar reaction conditions as described above, were employed for indole (8a) and 2-methylindole (8b). Reaction of alkyl isocyanides with isopropylidene Meldrum's acid in the presence of 8a or 8b at room temperature in CH 2 Cl 2 leads to 9 (see Scheme 3).The essential structures of compounds 9a-f were deduced from their elemental analyses and 1 H NMR and 13 C NMR spectra as well as from the IR spectra, which exhibited NH band. The mass spectra of these products displayed molecular ...

A complementary site selective ortho- vs ipso-amination of aryl halides using non-electrophilic amine sources for construction of indole scaffolds is reported. A palladium-catalyzed alkyne insertion/C–H activation/palladacycle amination via merger of three easily diversified components including iodoarenes, alkynes, and amines delivers indoles with different substitution patterns even in gram scales. By employing ortho-bromoanilines, a consecutive annulative π-extension of indoles proceeds to construct indolo­[1,2-f]­phenanthridine scaffolds via four C–C and C–N bond formations in one pot.

No abstract

The novel coumarin‐3‐carboxamides (=2‐oxo‐2H‐1‐benzopyran‐3‐carboxamides) 5a–5g containing lipophilic spacers were synthesized through the Ugi‐four‐component reaction (Scheme 1). The reactions of aromatic aldehydes 1, 4,4′‐oxybis[benzenamine] or 4,4′‐methylenebis[benzenamine] as diamine 2, coumarin‐3‐carboxylic acid (=2‐oxo‐2H‐benzopyran‐3‐carboxylic acid; 3), and alkyl isocyanides 4 lead to the desired substituted coumarin‐3‐carboxamides 5a–5g at room temperature with high bond‐forming efficiency. These novel coumarin derivatives exhibit brilliant fluorescence at 544 nm in CHCl3.

A fast, high efficiency and environmentally friendly procedure for the synthesis of 2-aryl benzimidazole derivatives has been reported. Reaction between 1,2-phenylenediamine derivatives and arylidene malononitrile under aqueous media and also solvent-free conditions generates 2-aryl benzimidazole derivatives with a high yield.