Total 1H and 13C chemical shift assignment of indolizino[3,4,5-a,b]-isoindole and 2-methylthiobenz[f]imidazo[5,1,2-c,d]indolizine

The ¹H and ¹³C nmr spectral assignment of indolizino[3,4,5-a,b]isoindole and 2-methylthiobenz[f]-imidazo[5,1,2-c,d]indolizine are described. A concerted interpretation of the HMQC, HMQC-TOCSY, HMBC and nOe-difference experiments were used to assign the ¹H and ¹³C resonances of indolizino-[3,4,5-a,b]isoindole, whereas for 2-methylthiobenz[f]imidazo[5,1,2-c,d]indolizine a concerted interpretation of the COSY, HMQC and HMBC experiments were used to generate spectral assignments.     

Low-temperature 1H and 13C NMR spectra of N-substituted 1,2,3,4-tetrahydropyrazino[1,2-a]indoles

The temperature-dependent (1)H and (13)C NMR spectra of 2-(2-butynyl)-10-methyl-1,2,3,4-tetrahydropyrazino[1,2-a]indole (4) (as a representative example of 1-9) in CFCl(3) + CD(2)Cl(2) solution are described and discussed. Below 183 K, the hexahydropyrazine ring inversions become slow on the NMR time-scale and 4 exists in principle as two conformational diastereomers. In fact, only one was observed with the N-2 substituent in an equatorial position as shown by a low-temperature NOESY experiment. The energy barrier for conformational interchange was calculated from NMR data to be 8.3 kcal mol(-1) (1 kcal = 4.184 kJ), in agreement with quantum chemical calculations. Unambiguous assignments for all proton and carbon resonances of 1-9 were made using 1D (APT, DEPT, NOE difference) and 2D (COSY, NOESY, gHMQC, gHMBC) NMR techniques.     

Total assignment of the 1H and 13C NMR spectra of benzo[f][1]benzothieno[2,3-c]quinoline by inverse-detected two-dimensional NMR techniques

The proton and carbon nmr spectra of benzo[f][1]benzothieno[2,3-c]quinoline have been totally assigned using a combination of 2D nmr methods including concerted use of HMQC (heteronuclear multiple quantum correlation) and HMBC (heteronuclear multiple bond correlation) experiments.     

1H NMR spectra of the 2-trifluoroacetyl derivatives of benzo[b]furan and benzo[b]thiophene

The ¹H NMR spectra of the 2-trifluoroacetyl derivatives of benzo[b]furan and benzo[b]thiophene were recorded at 200MHz in two solvents, chloroform and acetone. A long-range coupling constant, 5J(HF), between the fluorine nuclei of the trifluoroacetyl group and H-3, of a value higher than 1 Hz, was measured. From the comparison of the ¹H chemical shifts of, and the solvent effects on, the trifluoroacetyl compounds and those of the corresponding 2-acetyl derivatives, and on the basis of an empirical interpretation of the ⁵J(HF) coupling constant, a predominant Z conformation was tentatively assigned to these derivatives.     

1H NMR spectra of benzo[b]furan,benzo[b]thiophene and benzo[b]selenophene oriented in a lyotropic mesophase

The proton nuclear magnetic resonance spectra of benzo[b]-furan, -thiophene and -selenophene oriented in a potassium laurate lyotropic liquid crystal have been analyzed. Geometrical information has been obtained and compared to previous thermotropic results and various hypothetical models.     

Studies on the benzo[1,2]cyclohepta[3,4,5-d,e]isoquinoline ring system

The syntheses of various oxidation states of the novel benzo[1, 2]cyclohepta[3, 4, 5-d, e]-isoquinoline ring system is described. The ring system was obtained by the Schmidt rearrangement, with exclusive alkyl migration, of 1, 6, 7, 11b-tetrahydro - 2H - dibenz-[cd,h]azulen-2-one and by a Bischler-Napieralski reaction of suitable derivatives of 10, 11-dihydro-5H-dibenzo[a, d]cycloheptene - 5 - methylamine. 4, 5, 10, 11 - Tetramethoxy derivatives of the new ring system were best prepared by a Pictet-Spengler reaction of the appropriate amine.     

1H, 13C and 15N NMR spectra of [1,2-15N2]pyrazole derivatives

The chemical shifts and coupling constants of [1,2-¹⁵N₂]pyrazole, 2-(1-[1,2- ¹⁵N₂]pyrazolyl)-2-[l,3-²H₆]propanol, 1-nitro[1,2¹⁵N₂] and 3-nitro[1,2-¹⁵N₂]pyrazole are reported.     

13C NMR spectra of benzo[b]thiophene and 1-(X-benzo[b]thienyl)ethyl acetate derivatives

Carbon-13 chemical shift assignments are reported for benzo[b]thiophene and 1-(X-benzo[b]thienyl)ethyl acetate derivatives, where X=? CH(OAc)CH₃ substituted at positions 2-7. Substituent chemical shift (SCS) effects for the ethyl acetate group are additive at all positions. A substantial upfield shift was observed at C-3, arising from the peri interaction of H-3 and the 4-ethyl acetate substituent. Carbon-13 relaxation times (T₁) and nuclear Overhauser enhancements (η) have been measured for benzo[b]thiophene and its derivatives, and the contributions of dipolar, T^DD₁, and spin rotation, T^SR₁, relaxation have been determined. Intramolecular dipole–dipole interactions are found to provide by far the most important spin-lattice relaxation mechanism whenever protons are bound directly to the carbons under investigation. Nonprotonated ring carbons are relaxed by both DD and SR mechanisms. Anisotropic motion has an easily observable effect on the DD contribution to T₁, and can form the basis for spectral assignments, as in 1-phenylethyl acetate. Long-range ¹³C? ¹H coupling constants were observed both between ring carbons and between ring carbons with ring side-chain hydrogens. These results have been used for the structure determination of the title compounds.     

Unequivocal total assignment of 13C and 1H NMR spectra of some pyrido[1,2‐a]pyrimidine derivatives by 2D‐NMR

We report the total assignments of the ¹³C and ¹H NMR spectra of some 4‐methyl‐2‐oxo‐(2H)‐pyrido[1,2‐a]pyrimidine and 2‐methyl‐4‐oxo‐(4H)‐pyrido[1,2‐a]pyrimidine derivatives. The products were characterized by ¹H and ¹³C NMR and reported data for similar compounds. No comparative data for the two sets of isomeric compounds with respect to ¹³C and ¹H NMR have been reported to date. We made some detailed studies of the 2D NMR spectra of these compounds and observed that assignments made for non‐protonated carbon atoms by us and those reported in the literature for similar compounds need correction. The revised assignments were made on the basis of heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) techniques. Copyright © 2003 John Wiley & Sons, Ltd.     

Complete 1H and 13C NMR spectral assignment of benzo[d]isothiazole derivatives and of an isoindole isoster

The complete (1)H and (13)C NMR assignments of the novel compound methyl 2-amino-3-(benzo[d]isothiazol-3-yl)propanoate (1), of 3-amino-5-methylbenzo[d]isothiazole (2) and N-(t-butyloxycarbonyl)-2-aminobenzo[d]isothiazol-3(2H)-one (3) and of the desulfurated isostere of 3, N-(t-butyloxycarbonyl)-2-aminoisoindolin-1-one (4), using 1D and 2D NMR techniques, including COSY, INADEQUATE, HSQC, and HMBC experiments are reported.     

NMR studies of sulphur heterocycles: III—13C spectra of benzo[b]thiophene and the methylbenzo[b]thiophenes

All carbon resonances in the title compounds have been unequivocably assigned. Steric effects in the peri substituted compounds have been compared with analogous effects in naphthalene and benzo[b]furan. The observed effects are not explained by current theory. Unusual deshielding steric shifts are observed at some carbons. Methyl substituent effects are not additive at any position in the sterically crowded 2,3-disubstituted compounds.     

1H and 13C NMR spectra of new 2-thiabicyclo[3.2.0]hept-3-enes

Three new compounds, one with the molecular formula C₆H₈S and two corresponding to C₇H₁₀S have been isolated together with the main product, divinyl sulphide, from the reaction products of acetylene with sodium sulphide. Structure determination through ¹H and ¹³C NMR with selective ¹³C? {¹H} decoupling, showed C₆H₈S to be a new heterocyclic compound, 2-thiabicyclo[3.2.0]hept-3-ene, and the two C₇H₁₀S compounds its exo- and endo-6-methyl derivatives. Since the spectral parameters of these heterocycles were not known, all possible structures corresponding to the molecular formulae were considered.     

Mass spectra of pyrrolo [1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives

The closeness of the electronic structures of the ions formed in the first act of disintegration of the ions is responsible for the monotypic character of the subsequent fragmentation of pyrrolo[1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives. The mass-spectrometric disintegration of the investigated systems has something in common with the fragmentation of thiazolo[3,2-a]benzimidazole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1124–1127, August, 1975.     

Total assignment of 1H and 13C NMR spectra of the alkaloid 3,3-diisopentenyl-N-methyl-2,4-quinoldione and novel reaction derivatives

One- and two-dimensional NMR experiments were used for the unambiguous assignment of the 1H and 13C NMR chemical shifts of 3,3-diisopentenyl-N-methyl-2,4-quinoldione and five novel reaction derivatives.     

Total structural assignment and absolute configuration of terreinol by 13C and 1H NMR

The carbon-carbon connectivity of terreinol, a new metabolite isolated from Aspergillus terreus, and its previous (13)C assignments were confirmed by a two-dimensional INADEQUATE experiment using a few milligrams of the compound with natural (13)C abundance. The carbon-carbon correlations were determined by computational analysis (with >99% probability) of this experiment. Additionally, the absolute configuration of terreinol was achieved indirectly via its corresponding secondary alcohol by the modified Mosher method allied to conformational analysis. The shielding effect of the phenyl group of methoxytrifluoromethylphenylacetic acid (MTPA) on the substituents of the carbonylic centre gave a fully regular Deltadelta(SR) sign distribution, allowing reliable assignment of the R configuration for terreinol.     

Efficient One-pot Synthesis of Pyrrolo[2,1-a]isoquinoline and Pyrrolo[1,2-a]quinoline Derivatives

A one-pot sequential reaction for efficient synthesis of pyrrolo[2,1-a]isoquinoline and pyrrolo[1,2-a]-quinoline derivatives has been developed. The reaction included firstly the Cu-catalyzed three-component reaction of isoquinoline(quinoline), acetylenedicarboxylate and alkynylbenzene and then Cs₂CO₃-promoted intramolecular cyclization reaction of initially formed 1-alkenyl-2-alkynyl-1,2-dihydroisoquinoline(1,2-dihydroquinoline).     

Analysis of the 1H and 13C NMR spectra of bicyclo[6.2.1]undecane ring systems

A detailed NMR analysis with full assignment of the ¹H and ¹³C spectral data for two polycyclic compounds is described. These compounds are derivatives of the product obtained from the pericyclic reaction between cyclopentadiene and tropone. Peculiar intriguing conformational features of these molecules are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

A new synthesis of imidazo[1,2-a]pyridine and imidazo[2,1-a]isoquinoline derivatives

A new synthesis of imidazo[1,2-a]pyridine and imidazo[2,1-a]isoquinoline derivatives 4 and 8 , respectively by 1,5-dipolar cyclization reactions of stabilized pyridinium N-ylides 3a-e or isoquinolinium N-ylide 7 is described. The starting N-ylides 3a-e and 7 are prepared by the reaction of the corresponding pyridinium salts 1a-e or isoquinolinium salts 6 with N-bis(methylthio)methylene-p-toluenesulfonamide (2) .     

The 13C NMR spectra of 1,2,3-triazolo[1,5-a]pyridine and some monodeuteriated derivatives

The ¹³C signals of 1,2,3-triazolo[1,5-a]pyridine (1) are assigned, using the corresponding 3-, 6- and 7-deuterio-heterocycles; coupling constants are also given for compound 1.     

13C and1H NMR spectra and structure of 2-aryl-1,3-dibenzoyl-1,3-diazabicyclo[3.3.1]nonanes

Conclusion ¹³C and¹H NMR spectroscopy was used to determine the structures of 2-aryl-1,3-dibenzoyl-1, 3-diazabicyclo[3.3.1]nonanes and 2-aryl-1-benzyl-3-benzoyl-1,3-diazabicyclo[3.3.1]nonane. These compounds were found to exist predominantly in the boat-chair conformation (boat for the diaza ring), while the 2-aryl substituents occupy the exo or endo position.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1023–1028, May, 1988.