Complete assignment of the 1h- and 13c-nmr spectra of [1]benzothieno[2,3-c]naphtho[1,2-h]quinoline and [1]benzothieno[2,3-c]naphtho[1,2-h][1,2,4]triazolo[4,3-a]quinoline. Concerted use of two-dimensional nmr techniques

The ¹H- and ¹³C-nmr spectra of [1]benzothieno[2,3-c]naphtho[1,2-h]quinoline and [1]benzothieno[2,3-c]-naphtho[1,2-h][1,2,4]triazolo[4,3-a]quinoline were totally assigned using a combination of two-dimensional nmr techniques. After correlation of the proton signals by a COSY spectrum and one-bond heteronuclear correlation, complete assignment of the ¹H- and ¹³C-nmr spectra of the novel heterocyclic compounds required the application of long-range CH coupling information particularly for quarternary resonance assignments and the orientations of individual spin systems relative to one another.     

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.     

Total assignment of the 1H and 13C NMR spectra of pyrrolizino-[3,4,5-a,b]isoquinoline,benzo[1,2]pyrrolizino[3,4,5-a,b]isoquinoline and 2-methylthiopyrrolizino[3,4,5-a,b]isoquinoline

The total ¹H and ¹³C nmr spectral assignments of pyrrolizino[3,4,5-a,b]isoquinoline, benzo-[1,2]pyrrolizino[3,4,5-a,b]isoquinoline and 2-methylthiopyrrolizino[3,4,5-a,b]isoquinoline are reported. The concerted use of the COSY, HMQC, HMBC and nOe-difference experiments is used to generate total assignments of the ¹H and ¹³C nmr spectra.     

Assignment of the 1H- and 13C-NMR spectra of phenanthro[1,2-b]thiophene through the concerted application of two-dimensional NMR spectroscopic techniques

Two-dimensional nmr spectroscopy, by virtue of its second frequency domain which permits the segregation of spectral information along two frequency axes, considerably simplifies many assignment problems and facilitates others which may be impossible using conventional nmr methodology. A compound which falls into the latter category of assignment problem is phenanthro[1,2-b]thiophene. The assignment of the ¹H- and ¹³C-nmr spectra of phenanthro[1,2-b]thiophene are, however, reported through the concerted application of two-dimensional nmr techniques. Experiments utilized in making the assignments included: auto-correlated homonuclear (COSY) two-dimensional spectroscopy; heteronuclear two-dimensional J-resolved spectroscopy; proton-carbon chemical shift correlation two-dimensional spectroscopy; and two-dimensional ¹³C-¹³C double quantum coherence spectroscopy.     

The complete 1H and 13C chemical shift assignments of a cyclopropylpyrroloindole analog: Adozelesin

The ¹H and ¹³C nmr spectral assignments of [7bR]-N-[2-[(4,5,8,8a-tetrahydro-7-methyl-4-oxocyclo-propa[c]pyrrolo[3,2-e]indol-2(1H)-ylcarbonyl]-1H-indol-5-yl]-2-benzofurancarboxamide (Adozelesin) (1) are described. Complete and unambiguous assignments of the hydrogen and carbon spectra were made using a combination of conventional homonuclear and gradient-selected inverse-detected heteronuclear nmr experiments: double quantum filtered ¹H-¹H correlation spectroscopy (COSY), gradient-selected heteronuclear single quantum coherence spectroscopy (gs-HSQC), and gradient-selected heteronuclear multiple bond coherence spectroscopy (gs-HMBC). The enhanced sensitivity of these experiments allowed a smaller sample concentration and shorter spectral collection times for a full nmr analysis of this compound. The nmr data corroborates the published structure of this compound.     

Assignment of the proton and carbon NMR spectra of the indoloquinoline alkaloid cryptolepine

The relatively rare alkaloid cryptolepine, 5-methyl-5H-indolo[3,2-b]quinoline, was isolated from Cryptolepis sanguinolenta (Lindl.) Schlecter (Asclepiadaceae). Unequivocal proton and carbon nmr assignments in dimethyl sulfoxide are reported based on two-dimensional nmr methods, including COSY, inverse-detected direct (HMQC), and long-range (HMBC) correlations. Several of the assignments were confirmed using one-dimensional SIMBA spectra - a new, selective, one-dimensional analogue of the proton-detected long-range heteronuclear shift correlation experiment (HMBC). The SIMBA experiment was also used in an attempt to observe a two-bond coupling from the H11 proton to C10a at several optimizations.     

The first synthesis of thieno[c]isoquinolines and an improved synthesis of phenanthridine and thieno[c]quinolines through pd(0) catalyzed coupling of ortho-formylarylboronic acids with functionalized aryl halides

All three isomeric hitherto unknown thieno[c]isoquinolines have been synthesized in high yields by the Pd(0)-catalyzed coupling of 2-formylbenzeneboronic acid with t-butyl-N-(ortho-halothienyl)carbaniates. When 2-bromoacetanilide, instead of 2-bromoaniline, was coupled with orth-formylarylboronic acids under Pd-catalysis, phenanthridine and thieno[c]quinolines were obtained in improved yields. Total assignments of ¹H nmr spectra of thieno[c]isoquinolines and thieno[c]quinolines are reported. Assignments are based on high resolution 300 MHz ¹H nmr spectra, two-dimentional ¹H-¹³C chemical shift correlation spectra and one-dimentional INADEQUATE ¹³C nmr spectroscopy.     

Proton,carbon-13 and fluorine-19 NMR studies of 9,10,11,12-tetra-fluoro-5,6-dihydrobenzo[b]naphth[2,1-f]oxepin: ‘Through-space’ carbon-fluorine coupling was revealed

The ¹H, ¹³C and ¹⁹F nmr spectra of 9,10,11,12-tetrafluoro-5,6-dihydrobenzo[b]naphth[2,1-f]oxepin ( 1 ) were totally assigned using a combination of two-dimensional nmr techniques. Unequivocal interpretation of the spectral data allowed the complete assignments of the resonances. In addition, the spectra of compound 1 revealed an unusual through-space carbon-fluorine coupling which was further supported by NOE and modeling experiments.     

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.     

Assignment of the 1H- and 13C-NMR spectra of congested helicenes using two-dimensional NMR methods: Phenanthro[3′,4′:3,4]phenanthro[2,1-b]thiophene

Phenanthro[3′,4′:3,4]phenanthro[2,1-b]thiophene has been prepared and its highly congested proton and carbon nmr spectra assigned. The nmr assignments required concerted utilization of two-dimensional nmr techniques which included: COSY, direct and long range optimized heteronuclear chemical shift correlation and heteronuclear relayed coherence transfer.     

Benzannelated analogs of phenanthro[1,2-b]- and [2,1-b]thiophene: Synthesis and structural characterization by two-dimensional NMR and X-ray techniques

Syntheses of benzo[3,4]phenanthro[1,2-b]thiophene, benzo[3,4]phenanthro[2,1-b]thiophene and their 1-methyl analogs are reported as potential constituents of solvent refined coal liquids and for mutagenicity testing. The attempted synthesis of the 13-methyl analogs which gave the 11-methyl isomers is also described. Total assignments of the ¹H- and ¹³C-nmr spectra based on long range optimized heteronuclear protoncarbon two-dimensional chemical shift correlation are reported. Carbon assignments obtained for benzo[3,4]-phenanthro[1,2-b]thiophene using this approach were confirmed with a 125 MHz ¹³C–¹³C INADEQUATE spectrum. X-Ray crystal structures were determined for benzo[3,4]phenanthro[1,2-b]thiophene and 1-methyl-benzo[3,4]phenanthro[2,1-b]thiophene. Both molecules were helically distorted from planarity. Close intramolecular contacts between the bay region H1–H13 and ClMe-H13 of 2.03 and 2.28 Å, respectively, were responsible for the distortions. There were no close intermolecular contacts of <3.5Å. both molecules refined to an R value of <0.05.     

NMR study of 1-azatricyclo[3.3.1.13-7]decane derivatives

1-Azatricyclo[3.3.1.1^3-7]decan-4-one (4-oxo-1-azaadamantane) and 1-azatricyclo[3.3.1.1^3-7]decane-4-α(β)-ol (4-α-(β)-hydroxy-1-azaadamantane) have been studied by ¹H and ¹³C nmr methods. From this study several stereo and stereoelectronic effects have been deduced. The complete proton and carbon chemical shift assignments for the title compounds have been made, with the aid of two-dimensional nmr techniques.     

1H and 13C NMR Spectra of 9H-Pyrimido[4,5-b]indoles

Based on analysis of ¹H and ¹³C NMR spectra of 9H-pyrimido[4,5-b]indole and its 4-phenyl-2-substituted derivatives, we have made assignments for the signals from the ¹H and ¹³C atoms of these compounds.     

Cage compounds IV. 1H and 13C NMR study of 3,6-epoxypentacyclo-[6.2.2.02,7.04,10.05,9]dodecane and 3,6-epoxypentacyclo-[6.2.1.02,7.04,10.05,9]undecane

The complete ¹H and ¹³C NMR assignments for 3,6-epoxypentacyclo[6.2.2.0^2,7.0^4,10.0^5,9]dodecane and 3,6-epoxypentacyclo[6.2.1.0^2,7.0^4,10.0^5,9]undecane are reported. The difference between the ¹H and ¹³C chemical shifts and one-bond proton-carbon coupling constants of these two compounds are adequately explained by the difference in the hybridization of the C? H bonds.     

Autocorrelated 13c-13c double quantum coherence two-dimensional nmr spectroscopy: Utilization of a modified version of the technique as an adjunct in the total assignment of the 1h- and 13c-nmr spectra of the mutagen phenanthro[3,4-b]thiophene

Development of successively higher field nmr spectrometers has facilitated the study of increasingly more complex molecules, although smaller molecules such as phenanthro[3,4-b]thiophene still offer very substantial assignment problems because of the highly congested nature of their ¹H- and ¹³C-nmr spectra. Assignments of such spectra, if they are to be unequivocal, frequently require the utilization of two-dimensional nmr spectroscopic techniques. Total assignments of the ¹H- and ¹³C-nmr spectra of phenanthro[3,4-b]thiophene are reported. Assignments were based on a conventional high resolution 500 MHz ¹H-nmr spectrum, autocorrelated two-dimensional ¹H-nmr spectra (COSY), two-dimensional ¹H-¹³C chemical shift correlation spectra and a modified version of autocorrelated ¹³C-¹³C double quantum coherence two-dimensional nmr spectroscopy. From NOE measurements, a separation of 1.99 Å between H1 and H11 was computed, suggesting that phenanthro[3,4-b]thiophene has a pronounced helical conformation in solution.     

On the chemistry of pyrrole pigments: 57—Phytochrome model studies: Complete assignments of the 13C NMR spectra of phytochrome model compounds

A strategy for the assignment of aromatic ¹³C NMR resonances of pyrrole pigments is presented which makes use of two-dimensional chemical shift correlation spectroscopy via one-bond and long-range C,H coupling constants. The complete ¹³C NMR assignments for a 3,4-dihydropyrromethenone and three phytochrome model compounds (2,3-dihydrobilatrienes-abc) are given.     

Application of 1H and 13C NMR to the structural elucidation of tetrahydroquinoxalines condensed with five-membered heterocycles

¹H and ¹³C NMR spectral data for 21 N-methyltetrahydroquinoxalines annelated with furan, pyrrole, imidazole or thiazole rings are reported. Unambiguous assignments of the ring junction ¹³C resonances were made on the basis of selective decoupling experiments and with the aid of one-bond and long-range ¹³C–¹H coupling constants. The effects of five-membered heterocycles on the ¹H and ¹³C chemical shifts of the ring junction hydrogen and carbon atoms are considered. Values of one-bond ¹J(CH) and vicinal ³J(HH) coupling constants between the ring junction protons are also discussed as a diagnostic means for structural elucidation of tetrahydroquinoxalines condensed with five-membered heterocycles.     

A synthetic entry into the quino[2,1-b][1,3]benzoxazine ring system

The double ring closure of N-(2-hydroxybenzyl)anthranilic acids 1 with acetic anhydride or its acyclic analogous (RCH₂CO)₂O 2b and 2e lead to the formation of novel 12H-quino[2,1-b][1,3]benzoxazin-5-ones. The structure of the obtained compounds was proved with the use of their ir, mass, ¹H and ¹³C nmr spectra. Homo- and heteronuclear two-dimensional nmr experiments were performed to unambiguously assign all proton and carbon chemical shifts.     

The synthesis of novel polycyclic heterocyclic ring systems.. Benzo[e][1]benzothieno[3,2-g][1]benzothiophenes

The novel polycyclic heterocyclic ring system compound, methyl 3-chlorobenzo[e][1]benzothieno-[3,2-g][1]benzothiophene-2-carboxylate was synthesized. The assignment of its ¹H and ¹³C nmr spectra was also accomplished by utilizing two-dimensional nmr methods.     

Synthesis and spectroscopic characterizations of both 4b,5-dihydro-4b-methyl-11H-isoindolo[2,1-a]benzimidazol-11-ones and 2,3,3a,4-tetrahydro-3a-methyl-1H-pyrrolo[1,2-a]benzimidazol-1-ones

The complete assignment of the ¹H and ¹³C nmr spectra of some derivatives of both 4b,5-dihydro-4b-methyl-11H-isoindolo[2,1-a]benzimidazol-11-one I and 2,3,3a,4-tetrahydro-3a-methyl-1H-pyrrolo[1,2-a]-benzimidazol-1-one II was herein reported by the combined use of one and two-dimensional nmr techniques. Eight compounds, three of which are novel, 2a, 3, 6 , were thus prepared. Their uv and ir spectra were also obtained. In addition, the mass spectra of compounds 1, 2a, 2b, 3 and 6 are reported.