Regioselective Synthesis of 1,2-Dihydroquinolines by a Solvent-Free MgBr₂-Catalyzed Multicomponent Reaction

Abstract

A highly efficient and regioselective synthesis of 1,2-dihydroquinolines via a multicomponent reaction between an aniline and two ketones is described. This reaction was catalyzed by magnesium bromide and carried out under solvent-free conditions. When the reaction was performed by using 3-substituted anilines and nonsymmetrically substituted ketones, principally a single product was found among the four expected regioisomers. A variety of anilines and ketones, including cyclic ketones, were evaluated providing a series of 1,2-dihydroquinolines with diverse substitution patterns. A study of the mechanism is discussed. There is evidence of the in situ formation of the imine as a result of the reaction between the aniline and one of the ketones, before annulation to the heterocyclic ring.

Domino Processes of Arynes Reacting with Three Classes of Nucleophiles for Organic Syntheses

“…invent an aza‐Michael/Aldol reaction for the asymmetric synthesis of 1,2‐dihydroquinolidines by using organo catalysts. Tamariz et al [30] . report a solvent‐free MgBr 2 ‐catalyzed multicomponent reaction.…”

“…Córdova et al [29] invent an aza-Michael/Aldol reaction for the asymmetric synthesis of 1,2dihydroquinolidines by using organo catalysts. Tamariz et al [30] report a solvent-free MgBr 2 -catalyzed multicomponent reaction. Rueping and co-workers [31] perform an asymmetric synthesis of dihydroquinolines through a combined metal catalysis and organo catalysis process.…”

Synthesis of a Series of 2-Indolylmethylene-Linked Compounds by Thermal Knoevenagel Condensation Under Catalyst- And Solvent-Free Conditions

“…Organic reactions under solvent-free and catalyst-free [18][19][20][21][22][23] conditions have increasingly attracted interest of chemists, particularly from the viewpoint of green chemistry. Though a number of solvent-free methodologies are known for effecting Knoevenagel condensation 13,15,16,24 , only a few catalyst-free reaction conditions are reported 25,26 .…”

Brønsted‐Acid‐Catalyzed Substrate‐Controlled and Site‐Selective Friedel–Crafts Alkylation: A New Strategy for Post‐Modification of 1,2‐Dihydroquinolines

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Av ariety of C3-, C6-, C8-and C13-functionalized 1,2-dihidroquinolines (1,2-DHQs)h ave been prepared through post-modification of simple 1,2-DHQs by regioselective Friedel-Crafts alkylations. For example, transition metals such as palladium, [8] ruthenium,s ilver,a nd gold catalyzed reactions of anilines with alkynes, [9] (Scheme 1a); scandium triflate, [10] silicotungstic acid, [11] HNO 3 , [12] iodine, [13] zeolite, [14] MgBr 2 and Li 2 CO 3 , [15] organo-catalyst [16] catalyzed reactions of anilines with ketones and other miscellaneous methodsw ith specific substrates [17] (Scheme 1a). For instances, 1, 2-DHQs were widely used as antibacterial, [1] antitrypanosomal, [2] antioxidant [3] anda ntidiabetic agents, [4] anti-juvenile hormonei nsecticides, ( Figure 1).

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“…For example, transition metals such as palladium, [8] ruthenium,s ilver,a nd gold catalyzed reactions of anilines with alkynes, [9] (Scheme 1a); scandium triflate, [10] silicotungstic acid, [11] HNO 3 , [12] iodine, [13] zeolite, [14] MgBr 2 and Li 2 CO 3 , [15] organo-catalyst [16] catalyzed reactions of anilines with ketones and other miscellaneous methodsw ith specific substrates [17] (Scheme 1a). Recently,e fficient strategies toward the synthesis of dihydroquinolines have been focusedo nac atalytic version.…”