1H,13C and 19F NMR data of N‐substituted 6‐(4‐methoxyphenyl)‐7H‐pyrrolo[2,3‐d]pyrimidin‐4‐amines in DMSO‐d6

Chemical shift assignment of seven N‐substituted 6‐(4‐methoxyphenyl)‐7H‐pyrrolo[2, 3‐d]pyrimidin‐4‐amines, six of which are fluorinated, have been performed based on ¹H, ¹³C, ¹⁹F, and 2D COSY, HMBC and HSQC experiments. Copyright © 2009 John Wiley & Sons, Ltd.     

Stereochemical assignments of aldol products of 2‐arylimino‐3‐aryl‐thiazolidine‐4‐ones by 1H NMR

The aldol reactions of 2‐arylimino‐3‐aryl‐thiazolidine‐4‐ones with benzaldehyde carried out at ?78 °C were found to produce sec‐carbinols. Intramolecular hydrogen bonding within the aldol products forming a six‐membered ring enabled the assignment of stereochemistries of the major and minor diastereomers via analysis of the syn and anti ³J_H,H ¹H NMR coupling constants. Copyright © 2012 John Wiley & Sons, Ltd.     

Discrimination of pseudo‐meta and pseudo‐para diamino‐octafluoro[2.2]paracyclophanes by 1H, 19F,and 13C NMR

Pseudo‐meta and pseudo‐para diamino‐octafluoro[2.2]paracyclophanes are challenging to separate either by chromatography or recrystallization, but through the use of a mixture of the two isomers, the ¹H, ¹⁹F, and ¹³C NMR spectra of these compounds have been fully and unambiguously assigned using ¹H COSY, ¹H‐¹⁹F HOESY, ¹H‐¹³C HSQC, ¹H‐¹³C HMBC, and ¹⁹F‐¹³C HSQC techniques. This permits the easy identification of either of the individual isomers. In addition, the ¹³C spectrum of the pseudo‐ortho analogue is reported and assigned for the first time. The gem shift effect in this series of bridge‐fluorinated paracyclophanes serves to deshield ¹H resonances and shield ¹³C. Copyright © 2012 John Wiley & Sons, Ltd.     

The first automated 470.59 MHz 19F NMR‐controlled titration: dissociation constants and ion‐specific chemical shifts of 2‐amino‐4‐fluoro 2‐methylpent‐4‐enoic acid

2‐Amino‐4‐fluoro‐2‐methylpent‐4‐enoic acid, obtained as a 1 : 1 salt with trifluoro‐acetic acid, was characterized by ¹H and ¹⁹F high‐resolution NMR spectroscopy. High‐precision potentiometry led to the dissociation constants pK = 1.879 and pK = 9.054. The first automated 470.59 MHz ¹⁹F NMR‐controlled titration yielded the dynamic chemical shift 〈δ_F〉 as a function of pcH or τ and the ion‐specific chemical shifts: δ_F(H₂L⁺) = ?94.81 ppm, δ_F(HL) = ?94.21 ppm, δ_F(L^?) = ?92.45 ppm. The deprotonation gradients were found to be Δ₁ = ?0.60 ppm and Δ₂ = ?1.76 ppm. Copyright © 2002 John Wiley & Sons, Ltd.     

Investigation of the correlations between 19F and 1H NMR signals for various mono‐ and di‐substituted octafluoro[2.2]paracyclophanes

A selection of mono‐ and pseudo ortho di‐substituted octafluoro[2.2]paracyclophane derivatives were analyzed using ¹⁹F‐¹H HOESY, ¹H COSY and ¹⁹F COSY techniques. This resulted in the unambiguous assignment of the ¹⁹F and ¹H NMR resonances, and also revealed interesting solvent effects and noteworthy coupling patterns for various J_HH, J_HF, and J_FF interactions, including observable through bond ⁷J_FF and ⁸J_FF couplings. For the four mono‐substituted derivatives, the assignments were achieved through the combination of ¹⁹F‐¹H HOESY, ¹H COSY and ¹⁹F COSY techniques. The C₂ symmetry of the six pseudo ortho di‐substituted derivatives that were examined produced simplified spectra, and careful inspection of the characteristic ¹H coupling patterns led to the assignment of ¹H signals. Therefore only ¹⁹F‐¹H HOESY experiments were required to complete the assignments for those molecules. Refinements and alternative strategies for previous protocols are presented for the molecules that were less responsive to nuclear Overhauser effect (nOe) experiments. Copyright © 2009 John Wiley & Sons, Ltd.     

1H and 13C NMR analysis of 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamido‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamide derivatives

The complete assignment of the ¹H and ¹³C NMR spectra of various 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamide‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamides with p‐methoxy, o‐chloro and m‐chloro substituents is reported. Copyright © 2013 John Wiley & Sons, Ltd.     

Through‐space 19F–19F spin–spin coupling in ortho‐fluoro Z‐azobenzene

We report through‐space (TS) ¹⁹F–¹⁹F coupling for ortho‐fluoro‐substituted Z ‐azobenzenes. The magnitude of the TS‐coupling constant (^TSJ_FF) ranged from 2.2–5.9 Hz. Using empirical formulas reported in the literature, these coupling constants correspond to non‐bonded F–F distances (d_FF) of 3.0–3.5 Å. These non‐bonded distances are significantly smaller than those determined by X‐ray crystallography or density functional theory, which argues that simple models of ¹⁹F–¹⁹F TS spin–spin coupling solely based d_FF are not applicable. ¹H, ¹³C and ¹⁹F data are reported for both the E and Z isomers of ten fluorinated azobenzenes. Density functional theory [B3YLP/6‐311++G(d,p)] was used to calculate ¹⁹F chemical shifts, and the calculated values deviated 0.3–10.0 ppm compared with experimental values. Copyright © 2015 John Wiley & Sons, Ltd.     

Heterocyclic analogs of xanthiones: 5,6‐fused 3‐methyl‐1‐phenylpyrano[2,3‐c]pyrazol‐4(1H) thiones—synthesis and NMR (1H, 13C, 15N) data

Various [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐ones with Lawesson's reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts (¹H, ¹³C, ¹⁵N) and coupling constants (¹H,¹H; ¹³C,¹H) was achieved by the combined application of various one‐ and two‐dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most ¹³C,¹H spin coupling constants is accomplished by 2D (δ, J) long‐range INEPT spectra with selective excitation. Copyright © 2010 John Wiley & Sons, Ltd.     

Complete assignment of 1H and 13C NMR spectra of α‐phenylsulfinyl‐N‐methoxy‐ N‐methylpropionamide and some p‐substituted derivatives

The complete assignment of the ¹H and ¹³C NMR spectra of the diastereomeric pairs of some α‐arylsulfinyl‐substituted N‐methoxy‐N‐methylpropionamides with the substituents methoxy, methyl, chloro, nitro is reported. Copyright © 2008 John Wiley & Sons, Ltd.     

General model of assignment of the relative stereochemistry in the Nicholas reaction products resulting from chiral dicobalthexacarbonyl‐1‐alkoxy‐propargylium cations

The Nicholas reaction of chiral 1‐alkoxy‐dicobalthexacarbonyl‐propargylium cations with linear and/or cyclic silyl enol ethers resulted in the formation of two pairs of diastereoisomers (syn‐1, syn‐2 and anti‐1, anti‐2), depending on the relative stereochemistry of the two new stereocenters formed in the reaction products. Here, we present a model to establish the relative stereochemistry of those stereocenters on the basis of a correlation of their ¹H and ¹³C NMR spectra, together with their conformational analysis and a study of the stereoelectronic interactions conditioning the chemical shifts and coupling constants. The importance of this method is based on its applicability to the assignment of the relative stereochemistry of non‐separable components of a diastereomeric mixture or, when diastereomers are non‐crystallizable oily products, not suitable for X‐ray diffraction analysis. Copyright © 2002 John Wiley & Sons, Ltd.     

Fluorine–proton correlation from isolated trifluoromethyl groups using unresolved J‐couplings

Fluorine‐containing compounds are rare in biological systems, so fluorine NMR spectroscopy can selectively detect and quantify fluorinated xenobiotics in crude biological extracts. The high sensitivity of fluorine NMR allows the detection of compounds containing isolated trifluoromethyl groups at nanogramme levels. However, it only provides limited structural information about trifluoromethyl‐containing compounds owing to the difficulty of interpreting fluorine chemical shifts and the low sensitivity of HOESY experiments used to correlate fluorine nuclei with protons in the same compound. This paper demonstrates that long‐range fluorine–proton J‐couplings can be used to correlate isolated trifluoromethyl groups with nearby protons with significantly higher sensitivity than HOESY. Fluorine‐observe fluorine–proton HMQC can even give correlations when the fluorine–proton J‐couplings are less than the observed fluorine resonance linewidth, so it provides a useful alternative source of structural information about fluorinated xenobiotics. Copyright © 2012 John Wiley & Sons, Ltd.     

Complete assignment of the 1H and 13C NMR spectra of antimicrobial 4‐arylamino‐ 3‐nitrocoumarin derivatives

Herein, we describe the synthesis and complete assignment of the ¹H and ¹³C NMR chemical shifts of a series of antimicrobial 4‐arylamino‐3‐nitrocoumarin derivatives based on a combination of ¹H and ¹³C NMR, ¹H‐¹H‐COSY, NOESY, HSQC and HMBC experiments. Conformational effects upon the chemical shifts of the coumarin moiety arising from the anisotropy of the aryl side group are briefly discussed. This study provides the first complete and fully assigned NMR data for this important group of antimicrobial compounds and bridges the gap existing in the literature with regard to NMR structural data for 4‐arylamino‐3‐nitrocoumarins. Copyright © 2010 John Wiley & Sons, Ltd.     

Photo‐induced cross‐linking mechanism in azide–novolac negative photoresists: molecular level investigation using NMR spectroscopy

Negative photoresists are composed of a photoactive component (aromatic azides/bisazides) and cyclized rubber or novolac resin dissolved in an organic solvent. Hydrogen abstraction and/or insertion reaction of the reactive nitrene intermediate formed during photoirradiation of the azide result in a cross‐linked network of the novolac resin. The molecular weight of novolac resin in the exposed part of the photoresist film thus increases compared with that of the unexposed part. This makes the exposed part insoluble in the alkaline developer. Exploiting this change in physical property, a pattern can be transferred to a substrate from a mask. A better understanding of the exact mechanism of cross‐linking reactions is very important to the design of a high‐performing negative photoresist. A quinone–imine‐type complex has been proposed earlier involving the aromatic moiety of novolac resin as the reaction site. A more recent study focuses the attack of nitrene on the methylenic bridge and hydroxyl group of novolac resins, which were found to be responsible for the cross‐linking reaction along with the aromatic moiety of novolac resin. However, in our study no evidence was found for the involvement of a methylenic hydrogen or aromatic moiety of novolac resin in the cross‐linking reaction. The ¹H NMR, ¹³C NMR and DEPT‐135 spectra before and after photolysis indicate that the cross‐linking site is predominantly the hydroxyl group of novolac resin. Multiple reaction sites of attack for the nitrene intermediate have been demonstrated in cashew nut shell liquid (CNSL)‐based novolac resin by ¹H NMR spectroscopy, which in turn further increases the cross‐linked network in the exposed part of a negative photoresist. Copyright © 2003 John Wiley & Sons, Ltd.     

Complete NMR assignment of (+)‐10β,14‐dihydroxy‐allo‐aromadendrane

The assignment of ¹H and ¹³C NMR of the sesquiterpene (+)‐10β,14‐dihydroxy‐allo‐aromadendrane by means of two‐dimensional NMR is reported. Copyright © 2003 John Wiley & Sons, Ltd.     

One‐Pot,Pseudo‐Five‐Component Synthesis of Bis[2‐(arylimino)‐1,3‐thiazolidin‐4‐ones]

Synthesis and characterization of bis[2‐(arylimino)‐1,3‐thiazolidin‐4‐ones] are described. The one‐pot, pseudo‐five‐component reaction of an aliphatic diamine, isothiocyanatobenzene, and dialkyl but‐2‐ynedioate at room temperature in anhydrous CH₂Cl₂ gives the title compound in relatively high yield. Under the same conditions, aromatic 1,2‐diamines yield 2‐(arylimino)‐N‐(enaminoaryl)‐1,3‐thiazolidin‐4‐ones in a pseudo‐four‐component reaction. Their structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme 3).     

Isolation and spectral study of 4‐methyl‐6,8‐dihydroxy‐7H‐benz[de]anthracen‐7‐one

4‐Methyl‐6,8‐dihydroxy‐7H‐benz[de]anthracen‐7‐one was isolated from the sap of Aloe by column chromatography. Its ¹H and ¹³C NMR spectra were completely assigned by utilizing two‐dimensional ¹H‐detected heteronuclear one‐bond (HMQC) and multiple‐bond (HMBC) chemical shift correlation experiments together with ¹H–¹H COSY and DEPT techniques. These techniques were also valuable in assigning the protons and carbons of those benzanthrone compounds which were previously incompletely reported because of the overlap of proton signals. The molecular structure was elucidated by 2D NMR analysis. The spectral properties (MS, IR and UV) are also presented. Copyright © 2003 John Wiley & Sons, Ltd.     

1H and 13C NMR spectral assignments of pyridinium salts linked to a N‐9 or N‐3 adenine moiety

¹H and ¹³ C NMR spectral data of 13 new compounds containing a 4‐(dimethylamino)‐ or 4‐(pyrrolidin‐1‐yl)pyridinium moiety linked to the N‐9 or N‐3 nitrogen atom of an adenine moiety were assigned. 1D and 2D NMR experiments (DEPT, HSQC and HMBC) allowed the unequivocal identification of N‐9 and N‐3 isomers. Copyright © 2012 John Wiley & Sons, Ltd.     

Complete assignment of NMR data of 22 phenyl‐1H‐pyrazoles' derivatives

Complete assignment of ¹H and ¹³C NMR chemical shifts and J(¹H/¹H and ¹H/¹⁹F) coupling constants for 22 1‐phenyl‐1H‐pyrazoles' derivates were performed using the concerted application of ¹H 1D and ¹H, ¹³C 2D gs‐HSQC and gs‐HMBC experiments. All 1‐phenyl‐1H‐pyrazoles' derivatives were synthesized as described by Finar and co‐workers. The formylated 1‐phenyl‐1H‐pyrazoles' derivatives were performed under Duff's conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydroacridines: Part 23. 1H and 13C NMR spectra of sym‐octahydroacridine,its 9‐(3‐pyridyl) and 9‐(4‐pyridyl) derivatives and the corresponding N(10)‐oxides. An experimental approach to the diamagnetic anisotropy of the pyridine nucleus

The complete ¹H NMR chemical shift assignments of 1,2,3,4,5,6,7,8‐octahydroacridine ( 1 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(3‐pyridyl)acridine ( 2 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(4‐pyridyl)acridine ( 3 ) and the corresponding N(10)‐oxides 1a , 2a and 3a , respectively, were achieved on the basis of 400 MHz ¹H NMR spectra and proton–proton decoupling, HMQC and NOEDIFF experiments. The spectral data for the above compounds provided the first experimental evidence of the difference in the anisotropy effect of the two non‐symmetrical moieties of the pyridine nucleus, and allowed us to ascertain that the shielding effect of the moiety defined by the C(2′)—N—C(6′) atoms is weaker than that of the C(3′)—C(4′)—C(5′) moiety. The ¹³C NMR spectra of 1 – 3 and 1a – 3a and the effect of N(10)‐oxidation on the ¹³C NMR chemical shifts are also discussed. The N‐oxidation of 2 and 3 with m‐chloroperbenzoic acid occurred regiospecifically, affording the N(10)‐oxides 2a and 3a free of N(1′)‐oxide isomers. Copyright © 2002 John Wiley & Sons, Ltd.