o-Benzenedisulfonimide as a reusable acid catalyst for an easy, efficient, and green synthesis of tetrahydroisoquinolines and tetrahydro-β-carbolines through Pictet–Spengler reaction

Abstract

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Experimental and Theoretical Observations on the Intramolecular Nucleophilic Addition of α‐Amino Carbanions to Arynes: Synthesis of 1‐Aryl‐1,2,3,4‐tetrahydroisoquinolines

“…The resulting oily mass, after usual work‐up and purification by column chromatography on silica gel, gave pure 1‐aryl‐1,2,3,4‐tetrahydroisoquinoline ( 14a ) in a low yield of 43 %. [12b], The yield of the product was then optimised by varying different reaction parameters, including the solvent, the amount of base, and the quenching temperature (Table ). Increasing the amount of base from 3 to 5 equiv.…”

“…1‐(4‐Methoxyphenyl)‐1,2,3,4‐tetrahydroisquinoline (14b): [12b] Brownish oil (160 mg, 50 %). 1 H NMR (400 MHz, CDCl 3 ): δ = 7.12–7.09 (m, 2 H), 7.07 (d, J = 3.8 Hz, 2 H), 6.98–6.94 (m, 1 H), 6.79–6.76 (m, 2 H), 6.69 (d, J = 7.6 Hz, 1 H), 5.01 (s, 1 H), 3.71 (s, 3 H), 3.21–3.15 (m, 1 H), 3.04–2.93 (m, 2 H), 2.80–2.73 (m, 1 H), 2.38 (br.…”

“…6,7‐Dimethoxy‐1‐(4‐methoxyphenyl)‐1,2,3,4‐tetrahydroisoquinoline (14i): [12c] Brown solid (185 mg, 54 %), m.p. 89–90 °C (ref.…”

“…6,7‐Dimethoxy‐1‐(3,4‐dimethoxyphenyl)‐1,2,3,4‐tetrahydroisoquinoline (14k): [12c] Yellow oil (184 mg, 52 %). 1 H NMR (400 MHz, CDCl 3 ): δ = 6.86 (s, 1 H), 6.79 (s, 2 H), 6.61 (s, 1 H), 6.25 (s, 1 H), 5.06 (s, 1 H), 3.86 (s, 3 H), 3.85 (s, 3 H), 3.82 (s, 3 H), 3.64 (s, 3 H), 3.25–3.19 (m, 1 H), 3.08–2.96 (m, 2 H), 2.82–2.73 (m, 1 H) ppm.…”

“…Warkentin and Tomaszweski have reported an intramolecular cyclisation method involving the addition of aryl radicals to imines for the synthesis of THIQ moieties . Along with these commonly known procedures, some other methods have also been developed …”