Bioglycerol-derived carbon−SO₃H as a recyclable catalyst for the synthesis of tetrahydro-β-carbolines

Abstract

A variety of aldehydes undergo smooth coupling with N-tosyltryptamine in the presence of carbon−SO3H in ethanol at 80 °C to furnish the corresponding tetrahydro-β-carbolines in excellent yields with high selectivity. The coupling of tryptamine with isatins affords the respective spiro-tetrahydro-β-carbolines in good yields. The use of a recyclable solid acid catalyst makes this method simple, convenient, and cost-effective.

Practical Stereoselective Synthesis of C3‐Spirooxindole‐ and C2‐Spiropseudoindoxyl‐Pyrrolidines via Organocatalyzed Pictet‐Spengler Reaction/Oxidative Rearrangement Sequence

“…White solid, 26.1 mg, 54% yield; 1 H, 13 C NMR charts were consistent with previously reported data [24] . 1 H‐NMR (400 MHz, CDCl 3 ) δ 7.82 (brs, 1H), 7.66 (d, J =8.2 Hz, 2H), 7.65–7.61 (m, 1H), 7.43 (d, J =8.0 Hz, 1H), 7.25–7.21 (m, 2H), 7.17–7.11 (m, 5H), 7.09–7.05 (m, 1H), 6.56 (s, 1H), 4.07–4.01 (m, 1H), 3.76–3.69 (m, 1H), 2.88–2.71 (m, 2H), 2.34 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 143.35, 140.05, 136.48, 136.10, 133.24, 130.98, 129.66, 129.54, 129.40, 127.86, 127.25, 126.23, 122.53, 122.37, 119.64, 118.23, 111.02, 108.67, 55.39, 42.30, 21.38, 20.55; IR (KBr) 3398, 1468, 1336, 1162, 768, 740, 658 cm −1 ; HRMS (ESI) calcd for C 24 H 21 BrN 2 O 2 SNa: m/z ([M+Na + ]) 503.0394, found 503.0396; [α] D 20 =−138.7 ( c =0.12, in CHCl 3 for 95% ee); HPLC Daicel ChiralPak IF column, n ‐Hexane/ i ‐PrOH=7/1, 1.0 mL/min, λ=280 nm, tR=19.0 min (minor isomer) and 30.4 min (major isomer).…”

“…White solid, 25.6 mg, 67% yield; 1 H, 13 C NMR charts were consistent with previously reported data [24] . 1 H NMR (400 MHz, CDCl 3 ) δ 7.70 (brs, 1H), 7.61 (d, J =8.4 Hz, 2H), 7.31–7.24 (m, 2H), 7.16–7.12 (m, 1H), 7.07–7.02 (m, 3H), 5.19 (m, 1H), 4.10 (dd, J =15.6 Hz, 7.2 Hz, 1H), 3.45–3.37 (m, 1H), 2.48–2.27 (m, 2H), 2.26 (s, 3H), 2.02–1.94 (m, 1H), 1.86–1.79 (m, 1H), 1.55–1.50 (m, 1H), 1.08(d, J =6.8 Hz, 3H), 0.99 (d, J =6.8 Hz, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ 143.16, 137.95, 135.73, 133.55, 129.32, 126.75, 126.66, 121.81, 119.30, 117.98, 110.77, 107.33, 51.48, 44.94, 39.01, 24.65, 23.38, 21.99, 21.31, 19.51; IR (KBr) 3359, 1327, 1160, 734, 653, 583 cm −1 ; HRMS (ESI) calcd for C 22 H 26 N 2 O 2 SNa: m/z ([M+Na + ]) 405.1607, found 405.1598; [α] D 23 =−79.3 ( c =0.19, in CHCl 3 for 84% ee); HPLC Daicel ChiralPak AD‐3 column, n ‐Hexane/ i ‐PrOH=7/1, 1.0 mL/min, λ=280 nm, tR = 13.2 min (major isomer) and 16.2 min (minor isomer).…”