Abstract
This paper describes a new strategy for the synthesis of 1‐trifluoromethyl‐ 9H‐pyrido[3,4‐b]indole 2 by one‐pot reaction of tryptophan methyl ester hydrochloride or tryptophan amide 1 and trifluoroacetic acid (TFA) in 60–78% yield via a possible intramolecular cyclization. The structures of 2a and 2e were confirmed by X‐ray crystallographic analysis.
Acknowledgment
This work was supported by the National Natural Science Foundation of China (No. 20272075).
Notes
1Crystal structure of 2a determination: Empirical formula: C14H9F3N2O2: Formula weight: 294.23. T = 273 (2) K. Wavelength: 0.71073 Å. Crystal system: Monoclinic, P2 1/n. Unit cell dimensions: a = 10.9191 (7) Å, α = 90°; b = 7.8212 (6) Å, β = 99.013 (3) °; c = 15.1663 (10) Å, γ = 90°. V = 1279.22 (15) Å3. Z = 4. ρCalcd = 1.528 g/m3. Absorption coefficient: 0.133 mm−1. F (000): 600. Crystal size: 0.29 × 0.27 × 0.07 mm3. Theta range for data collection: 2.15° to 25.02°. Limiting indices: −12 < h < 12, −9 < k < 7, −12 < l < 18. Reflections collected: 6450. Independent Reflections: 2260[R (int) = 0.0350]. Completeness to θ = 25.02°, 99.9%. Absorption correction: None. Max. and min. transmission: 0.9908 and 0.9625. Refinement method: Full‐matrix least–squares on F 2. Data/restraints/parameters: 2260/0/219. Goodness‐of‐fit on F 2: 1.438. Final R indices [I > 2σ (I)]: R 1 = 0.1361, wR 2 = 0.2070. R indices (all data): R 1 = 0.1407, wR 2 = 0.2089. Extinction coefficient: 0.0012 (12). Largest diff. peak and hole: 0.264 and −0.234 e Å−3. Crystal Structure of 2e Determination: Empirical formula: C17H15F3N2O2: Formula weight: 336.31. T = 298 (2) K. Wavelength: 0.71073 Å. Crystal system: Monoclinic, P2 1/n. Unit cell dimensions: a = 8.1231 (4) Å, α = 90°; b = 17.1197 (8) Å, β = 93.615 (2) °; c = 11.6388 (6) Å, γ = 90°. V = 1615.33 (14) Å3. Z = 4. ρCalcd = 1.383g/m3. Absorption coefficient: 0.115 mm−1. F (000): 696. Crystal size: 0.49 × 0.37 × 0.19 min3. Theta range for data collection: 2.12° to 25.01°. Limiting indices: −7 < h < 9, −20 < k < 20, −13 < l < 13. Reflections collected: 8369. Independent Reflections: 2850 [R (int) = 0.0321]. Completeness to θ = 25.01°, 99.9%. Absorption correction: Semi‐empirical from equivalents. Max. and min. transmission: 0.9785 and 0.9459. Refinement method: Full‐matrix least–squares on F 2. Data/restraints/parameters: 2850/0/227. Goodness‐of‐fit on F 2: 1.324. Final R indices [I > 26 (I)]: R 1 = 0.1756, wR 2 = 0.3339. R indices (all data): R 1 = 0.1813, wR 2 = 0.3369. Largest diff. peak and hole: 0.648 and −0.329 e Å−3.