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Metal-free rapid access to pyrrole-2,3-dione has been developed under mild conditions from easily available materials, which was utilized to synthesize pyrrolo[2,3-d]pyridazin-7-one's and pyrrolo[2,3-d]pyrizidines. The overall two-pot process proceeds through (i) the first pot, metal-free direct Mannich reaction-oxidative aromatization of succinaldehyde with C-acyl imine in situ generated to pyrrole-2,3-dione, and (ii) the second pot, further condensation with various hydrazines to synthesize several pyrrolo-pyrizidinones and pyrrolo-pyrizidines in moderate to good yields. [ABSTRACT FROM AUTHOR]

The synthesis of β-(C3)-functionalized pyrroles is a challenging task and requires a multistep protocol. An operationally simple direct catalytic synthesis of β-substituted pyrroles has been developed. This one-pot multicomponent method combined aqueous succinaldehyde as 1,4-dicarbonyl, primary amines, and isatins to access hydroxyl-oxindole β-tethered pyrroles. Direct synthesis of the β-substituted free NH-pyrrole is the central intensity of this work. DFT-calculations and preliminary mechanism investigation support the possible reaction pathway. [ABSTRACT FROM AUTHOR]

A sequential multicomponent synthesis of highly substituted pyrrole-3-carboxaldehydes has been developed under metal-free conditions. This one-pot protocol involves proline-catalyzed direct chemoselective Mannich reaction-cyclization between 1,4-ketoaldehyde and in situ generated Ar/HetAr-imines followed by aerobic oxidative-aromatization at room temperature. A series of fully substituted pyrrole-3-carboxaldehydes and other diverse fused heterocycles have been synthesized. These compounds were tested for in vitro antibacterial and antifungal activities, and the selected ones display significant activity against the tested bacterial strains with a MIC value of 16 μg mL−1, which is close to that of the standard drug chloramphenicol. The bioactivity outcome was further analyzed using docking studies. [ABSTRACT FROM AUTHOR]

A direct method for the synthesis of new tetracyclic oxazepine-fused pyrroles has been developed through [3+2] annulation between aqueous succinaldehyde and dibenzo[b,f][1,4]-oxazepines under metal-free conditions. This one-pot synthetic protocol involves proline-catalyzed direct Mannich/cyclization between aqueous succinaldehyde and seven-membered oxazepine-imines, followed by an IBX-mediated oxidation sequence with high yields (up to 90%). [ABSTRACT FROM AUTHOR]

A new method for one-pot synthesis of 2,3-substituted piperidine from N-PMP aldimine and aqueous glutaraldehyde via formal [4+2] cycloaddition is reported. This reaction involves organocatalytic direct Mannich reaction–reductive cyclization with high yields (up to 90%) and excellent enantioselectivities (up to ＞99%). The practicability of this method is also shown at a gram scale as well as through the synthesis of functionalized (−)-anabasine. [ABSTRACT FROM AUTHOR]

Amine catalysis, through HOMO-activating enamine and LUMO-activating iminium-ion formation, is receiving increasing attention among other organocatalytic strategies, for the activation of unmodified carbonyl compounds. Particularly, the HOMO-raising activation concept has been applied to the greatest number of asymmetric transformations through enamine, dienamine, and SOMO-activation strategies. Recently, trienamine catalysis, an extension of amine catalysis, has emerged as a powerful tool for synthetic chemists with a novel activation strategy for polyenals/polyenones. In this review article, we discuss the initial developments of trienamine catalysis for highly asymmetric Diels-Alder reactions with different dienophiles and emerging opportunities for other types of cycloadditions and cascade reactions.

A new method for asymmetric synthesis of 2,3-substituted pyrrolidines from N-PMP aldimines and succinaldehyde via formal [3+2] cycloaddition is reported. This reaction involves proline catalyzed direct Mannich reaction and acid catalyzed reductive cyclization with high yields (up to 78%) and excellent enantioselectivities (up to >99%).