NMR studies of indoles and their N‐carboalkoxy derivatives

Abstract

The 13C NMR assignment of indoles and 5-methoxyindoles substituted at position 3, and some of their N-carboalkoxy derivatives, was achieved from one-and two-dimensional NMR experiments. Substituent chemical shifts and 'J(CH) values were evaluated. The dynamic processes of N-carboalkoxyindoles and N-carboalkoxyindoline observed by high-field 'H NMR show the existence of two preferred rotamers around the carbamate N-C(=O)OR bond, which was interpreted in terms of frequency/field strength-dependent phenomena.

Configuration, stereodynamics and crystal structure of 3-substituted-2-oxofuro[2,3-b]indoles

“…The broadness of these signals suggests the presence of conformational isomers arising from slow rotation around the N-CO 2 Me bond. 8 Of additional interest is that the chemical shift of the proton (H-3) bonded to the carbon at which CN or CO 2 Me group is attached exhibits a strong solvent dependence. For example, the shift of H-3 for exo-1a is seen at δ 4.10 in CD 2 Cl 2 and δ 5.07 in (CD 3 ) 2 SO, whereas H-3 for exo-2a is seen at δ 3.90 in CD 2 Cl 2 and δ 4.28 in (CD 3 ) 2 SO, indicating hydrogen bonding associations involving the H-3 and the DMSO solvent.…”

Identification and Biological Evaluation of Secondary Metabolites from the Endolichenic Fungus Aspergillus versicolor

“…Theknown compounds were identified as diorcinol ( 16) [13], diorcinol D(17) [11], violaceol I(18) [23], cordyol C(19) [24], 3,7-dihydroxy-1,9-dimethyldibenzofuran (20) [14], violaceol II (21) [ 23], sydowic acid (22) [ 17], sydonic acid (23) [25], sydowiol A (24) [22], sydowiol B(25) [22], aversin (26) [26], 6,8-di-O-methylnidurufin (27)[27], 4hydroxybenzaldehyde (28) [ 28], and 3-formyl-1H-indole (29) [29]bycomparing their spectroscopic data (MS, [a] D ,U V, IR, and 1D-NMR)w ith those reported previously.…”

Electron ionization mass spectra of indolenines obtained using sector and ion trap mass spectrometers

“…This compound was prepared in 24% overall yield in two steps by refluxing methyl 1‐carbomethoxy‐3‐indolylcyanoacetate7 (1.0 g, 3.6 mmol) and sodium (84.3 mg) in diethyl carbonate (33 mL) for 30 min to give methyl 1‐carbethoxy‐3‐indolylcyanoacetate (32% yield, yellow oil); R f : 0.20 (1:4 EtOAc/hexane); IR (CHCl 3 ): ν max 3026, 2258, 1748, 1256 cm −1 ; 1 H NMR (CDCl 3 ): δ 8.24 (1H, br d, J = 8.7 Hz, H‐7), 7.86 (1H, s, H‐2), 7.66 (1H, dd, J = 8.9, 1.9 Hz, H‐4), 7.43 (1H, td, J = 8.7, 1.9 Hz, H‐6), 7.34 (1H, td, J = 8.9, 1.9 Hz, H‐5), 4.95 (1H, s, H‐8), 4.51 (2H, q, J = 7.1 Hz, OCH 2 ), 3.84 (3H, s, OCH 3 ), 1.49 (3H, t, J = 7.1 Hz, CH 3 ); 13 C NMR (CDCl 3 ) δ 164.8 (CO), 150.4 (NCO), 135.6 (C‐7a), 127.4 (C‐3a), 125.7 (C‐6), 125.1 (C‐2), 123.6 (C‐5), 119.0 (C‐4), 115.6 (C‐7), 114.9 (CN), 110.2 (C‐3), 63.8 (OCH 2 ), 54.1 (OCH 3 ), 35.4 (C‐8), 14.4 (CH 3 ). The product, in glacial acetic acid, was treated with HNO 3 following the procedure described5b for 1 , to give 5 in 76% yield; mp 161–163°C; R f : 0.11 (1:4 EtOAc/hexane); IR (CHCl 3 ): ν max 3026, 2222, 1724, 1590, 1272 cm −1 ; 1 H NMR (CDCl 3 ): δ 8.45 (1H, br d, J = 8.0 Hz, H‐4), 7.95 (1H, br, H‐7), 7.58 (1H, td, J = 7.9, 1.3 Hz, H‐6), 7.18 (1H, td, J = 8.0, 1.2 Hz, H‐5), 6.78 (1H, br s, H‐2), 4.41 (1H, br s, OH), 4.39 (2H, q, J = 7.3 Hz, OCH 2 ), 3.94 (3H, s, OCH 3 ), 1.42 (3H, t, J = 7.3 Hz, CH 3 ); 13 C NMR (CDCl 3 ): δ 161.2 (CO), 160.3 (C‐3), 152.0 (NCO), 147.1 (C‐7a), 137.2 (C‐6), 126.7 (C‐4), 124.0 (C‐5), 122.6 (C‐3a), 115.7 (C‐7), 115.4 (CN), 97.6 (C8), 83.0 (C2), 63.0 (OCH 2 ), 53.5 (OCH 3 ), 14.5 (CH 3 ).…”