Synthetic approaches towards indoles on solid phase recent advances and future directions

Heterogeneous Palladium Catalysts Applied to the Synthesis of 2- and 2,3-Functionalised Indoles

“…[1,2] The diversity of the structures encountered, as well as their biological and pharmaceutical relevance, have motivated research aimed at the development of new economical, efficient and selective synthetic strategies, particularly for the synthesis of functionalised indole rings. [3,4] Several classical methods have been reported, including the Fischer indole synthesis from arylhydrazones, [5,6] the Batcho-Limgruber synthesis from o-nitrotoluenes and dimethylformamide acetals, [7] the Gassman synthesis from N-haloanilines, [8,9] the Madelung cyclisation of Nacyl-o-toluidines [10 -12] and the reductive cyclization of o-nitrobenzyl ketones. [3] While these procedures have contributed to this important area, some remain limited when the synthesis of functionalised indoles is required.…”

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Abstract:Heterogeneous palladium catalysts ([Pd(NH 3 ) 4 ] 2 þ /NaY and [Pd]/SBA-15) were applied to the synthesis of 2-functionalised indoles, giving generally high conversions and selectivities ( > 89% yield) using only 1 mol % [Pd]-catalyst under standard reaction conditions (polar solvent, 80 8C). For the synthesis of 2,3-functionalised indoles by crosscoupling arylation, the [Pd]/SBA-15 catalyst was found to be particularly interesting, producing the expected compound with ¼ 35% yield after 12 days of reaction, which is comparable to the homogeneous catalyst, Pd(OAc) 2 ( ¼ 48% yield).

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Chirospecific synthesis: Catalysis and chiral pool hand in hand

“…Our understanding of the behavior of these molecules has required deeper theoretical understanding in their use [7]. Obviously, development of synthetic technologies is a natural extension of such chemical studies, and this has enticed us into applications in organocatalysis [8], solid-phase synthesis [9], and combinatorial chemistry [10]. The new potentials provided by the new chemistry have also lured us into journeying in bordering fields such as chemical biology [11,12].…”

Synthesis of 2-phenyl-5-sulpha/substituted-3- substituted phenyl azo indoles used as antifertility agent

“…Indenopyridines have been unique pharmacological properties, such as insecticidal, phosphodiesterase inhibiting, antifungal, antispermatogenic, antifertility, antagonistic and ant arrhythmic activities [12]. The diversity of the structure encountered, as well as their biological and pharmaceutical relevance, have motivated research aimed at the development of new economical, efficient and selective synthetic strategies, particularly for the synthesis of substituted indole rings [13,14]. Literature survey however reveals that no work have been done on sulpha/substituted indole and N-phenyl acyl sulpha/substituted azoindoles and their pharmacological activity.…”