N-(2-Aminobenzylidene)-4-methylanilines—stable and cheap alternate for 2-aminobenzaldehydes: concise synthesis of 3-unsubstituted-2-aroylindoles

Synthesis of 2-Acylindoles via Ag- and Cu-Catalyzed anti-Michael Hydroamination of β-(2-Aminophenyl)-α,β-ynones: Experimental Results and DFT Calculations

“…12 These procedures, although efficient, require the presence of a directing group linked to the N 1 atom of the indole, which allows activation of the C 2 −H bond by cyclometalation; hydrolytic cleavage is then necessary to obtain the free N−H indole. Other recent routes toward 3-unsubstituted 2-acylindoles include the reaction of sulfur ylides and N-(orthochloromethyl) aryl amides in the presence of cesium carbonate, 13 rhodium(I)-catalyzed reductive N-cyclization of 2-vinylnitroarenes using CO as a reducing agent, 14 reaction of 2-aminobenzaldehyde equivalents with αbromoketones, 15 Cu(I)-mediated cyclization of o-bromochalcones, 16 I 2 -mediated intramolecular α-amination of ketones, 17 and domino Pd-catalyzed cyclization of 2-gem-dibromovinylanilines-carbonylative Suzuki coupling. 18 The 5-endo-dig cyclization of 2-alkynylaniniles 1 through transition metal (TM)-catalyzed hydroamination represents an efficient and atom-economical tool for the preparation of 2substituted indole derivatives 2 (Scheme 1a).…”

Synthesis of Fused Quinoline Derivatives from Easily Accessible N‐(2‐aminobenzylidene)‐4‐methylanilines under Catalyst‐Free Conditions in Water

“…In our previous communication, we have demonstrated the utility of N ‐(2‐aminobenzylidene)‐4‐methylanilines as 2 aminoarylaldehyde equivalent for the synthesis of 3‐unsubstituted‐2‐aroylindoles [19] . In continuation of this work, herein, we report the synthesis of a variety of fused quinoline derivatives including pyrimido[4,5‐ b ]quinoline‐2,4(1 H ,3 H )‐diones,2‐thioxo‐2,3‐dihydropyrimido[4,5‐ b ]quinolin‐4(1 H )‐one, 6 H ‐chromeno[4,3‐ b ]quinolin‐6‐ones and 2,2‐dimethyl‐4 H ‐[1,3]dioxino[4,5‐ b ]quinolin‐4‐one starting from N ‐(2‐aminobenzylidene)‐4‐methylanilines and heterocyclic 1,3‐dicarbonylcompounds.…”

α-Hydroxydimethylacetal/ketal as an α-hydroxycarbonyl equivalent in interrupted Heyns/Amadori rearrangement: regioselective synthesis of substituted C2- and C3-acylindoles

“…Due to the inherent reactivity of the indole moiety, the synthesis of 3-acylindole derivatives 13 has been relatively well established compared to the 2-acylindoles. 14 However, most of the known strategies suffer from harsh conditions and poor regioselectivity, and require precious metal catalysts as well as pre-functionalized indoles as precursors, which limits their synthetic applicability. Therefore, the development of an unified, regioselective, metal-free and complementary strategy for the synthesis of 2- and 3-acylindoles is in high demand.…”