Nitrogen bridgehead compounds,part 68. Studies on quinolizine derivatives. Part 2. Synthesis of 1,3-disubstituted-4H-quinolizine derivatives

Quinolizine compounds 1 and 2 or their monocyclic tautomers 3 and 4 have been synthesized using 2-pyri-dineacetic acid derivatives 6a, b, A, B and ethoxymethylenemalonic acid derivatives 7a, b, c in base catalyzed or thermic reaction. In the 6-unsubstituted series, both the 4-oxo and 4-imino derivatives could have been obtained, in the 6-substituted series, however the 4-oxo ones only, whereas instead of the 4-imino derivatives, their monocyclic tautomers 3, 4 have been isolated. In the 6-unsubstituted series, the primarily formed 4-imino compounds have been rearranged into 4-oxo ones under stronger conditions. The structure of the isolated compounds have been proved by ultraviolet, infrared and ¹H nmr spectra, that of 3B=C by X-ray analysis as well.     

Nitrogen bridgehead compounds. Part 70. Studies on quinolizine derivatives. Part 4. Ultraviolet-visible spectra and chemical properties of some quinolizine derivatives and their monocyclic tautomers

Ultraviolet-visible spectra of 4-oxo 1 and 4-imino 2 quinolizines or their monocyclic tautomers 3, 4 have been studied in neutral, acidic and basic ethanolic solution as well as in dimethyl sulfoxide and chloroform. Ring B of 4-oxo and 6-unsubstituted 4-imino compounds can be cleaved by sodium ethanolate more or less easily. Ring B of 6-methyl-4-iminoquinolizines is very unstable and they are present mainly in the monocyclic form which are partly dissociated in ethanol and dimethyl sulfoxide especially in higher dilution or in the presence of sodium ethanolate. In dilute acidic ethanol or chloroform, the dissociation is suppressed and in the latter solvent and in some cases, absorption bands can be observed due to a small amount of the 4-imino-6-methylquinolizines. In acidic solution of compounds 3B=C, 3D, 4E, 4F=G having simultaneously cyano and ethoxycarbonyl groups in 1 and 3 position, not simple reprotonation occurs but irreversible changes can be observed.     

Conformational analysis of benzoannulated nine-membered rings. Part 3. 1,4,5,7-Tetrahydro-3H-2,6-benzodiselenine and its 4-spiro derivatives

The ¹H and ¹³C nmr spectra of 1,4,5,7-tetrahydro-3H-2,6-benzodiselenine (1) and three 4-spiro derivatives 2–4 as well as the ⁷⁷Se nmr spectra of 2 have been recorded at different temperatures in order to investigate their conformational behavior. It was found that in analogy to corresponding dithionins the molecules adopt a chiral ground state conformation (Figure 2), and coalescence effects are due to racemization.     

Reaction of 4-hydrazinoquinolines with β-diketones. Synthesis and spectroscopy (1h, 13c nmr,ms) of some pyrazolylquinolines

A series of 4-pyrazolylquinolines have been prepared from 4-hydrazinoquinolines and β-dicarbonyl compounds and the previously proposed diazepine structure for the reaction products has been ruled out. A ¹³C nmr study established the 3-position of the methyl group when two isomers were possible. Finally, a careful ¹H nmr study of 2- and 4-pyrazolylquinolines led to the conclusion that intramolecular hydrogen bonds between aromatic (or heteroaromatic) C-H and pyridine like nitrogens is the factor that determines the conformation of these compounds.     

Syntheses and spectral properties of 2-Thiobiotin and biotin derivatives

A series of methylated derivatives of 2-thiobiotin (2-4) have been prepared as potential aids in elucidation of the mechanism of biotin catalysis. The syntheses and mass, infrared, ¹H nmr, and ¹³C nmr spectral properties for these substrates, their 2-thiobiotin precursors (6, 10-14) and the corresponding biotin analogs (1, 15, 31-34) are described. A series of selective proton-proton and proton-carbon decoupling experiments were employed to secure a number of the ¹H and ¹³C nmr assignments. Consistent patterns noted throughout the data set proved helpful in structure determination.     

2‐(4‐methylpyridin‐2‐yl)‐1H‐benzimidazole derivatives. Part II,lH nmr characterization

A selected series of 2‐(4‐methylpyridin‐2‐yl)‐1H‐benzimidazole derivatives, bases and cyclic mono‐ and bis‐salts, were synthesized. Complete ^'1H nmr characterization is reported. Ambiguous assignments were solved using ¹H‐¹H NOESY analysis. Significant ir and ¹H nmr data are presented concerning: i) tautomeric equilibrium of imidazole hydrogen; ii) hydrogen bonds; iii) conformational inversion of partially saturated rings.     

Nitrogen bridgehead compounds. Part 76 Synthesis and stereochemistry of ethyl 9-benzylidene-6,7,8,9-tetrahydro-2-oxo-2H- and 4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylates and their homologues

Ethyl 4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylates 1–4 , their piperidine ring homologues 5–6 and their 2-oxo isomers 7–9 were reacted with benzaldehyde. At low temperature, kinetically stable addition products were formed. Thermodynamically stable condensation products were obtained at higher temperature, which were also formed when the addition products were refluxed in benzene. The 9-benzyl derivatives were prepared by the hydrogenation of the condensation products over Pd/C. The stereochemical features of the new compounds were determined via ¹H and ¹³C nmr chemical shift and coupling constant analysis and NOE measurements.     

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.     

Quinone chemistry. Synthesis and tautomerism of 4,7-indazolequinones

The reaction of 1 with hydrazines provided hydrazinium-4,7-dioxo-4,7-dihydroindazol-3-olates 2a-e and 4,7-indazolequinones 3f,g depending upon the nature of the substituent present in the reactants. Compounds 3a-g were obtained by treatment of 2a-e with sodium hydroxide. Fixed tautomers 4a-b and 5c-f were synthesized by methylation of the corresponding 3a-f or 2a-2e with diazomethane. Migration of a methyl group of 5c-f from the oxygen at C₃ to N₁ on heating afforded 6c-f . The tautomerism of 2a-e and 3a-g has been studied by comparing ir, uv, ¹H nmr and ¹³C nmr spectra with those of the fixed tautomers.     

Tetronic acids and derivatives. Part XI . Structure of coupling products of tetronic acids with benzenediazonium sulfate

¹³C Nmr, ¹H nmr and ir parameters of coupling products of tetronic acids (4-hydroxy-5H-furan-2-ones) with benzene diazonium sulfate are only consistent with a phenylhydrazone formulation with an almost equal ratio of the syn and anti configurations. These results contrast with those of coupling products of acyclic 3-ketoesters, existing mainly as anti tautomers, and more sharply with the 3-parabromophenylhydrazone of L-dehydro ascorbic acid, which is exclusively syn.     

Investigation in tetronic acid ketoxime derivatives. Structure and beckmann rearrangement. Synthesis of 3-acetamidotetronic acids

The structure and tautomeric equilibria of 3-(1-hydroxyiminoethylidene)tetronic acids have been investigated by ¹H and ¹³C nmr spectroscopy. These oximes are convertible into 3-acetamidotetronic acids.     

Carbon-13 nuclear magnetic resonance spectra of 1,2,3,4-tetrahydroquinazoline and some 3-benzyl derivatives

The concerted use of the ¹H/¹³C shift correlation with full ¹H/¹H decoupling and the modified COLOC sequence for long-range X/H correlation 2D nmr spectroscopy allows the total assignment of the ¹³C nmr resonances of 1,2,3,4-tetrahydroquinazoline and 3-benzyl-1,2,3,4-tetrahydroquinazoline. From these data, the ¹³C nmr chemical shifts of a series of 3-benzylsubstituted-1,2,3,4-tetrahydroquinazolines are deduced.     

Imination of N-methylpyridinium salts by liquid ammonia-potassium permanganate. A new synthesis of nudiflorine

Reaction of substituted 1-methyl(benzyl)pyridinium salts ( 1 ) with liquid ammonia/potassium permanganate leads to introduction of the imino group at the carbon adjacent to the nitrogen. The regiospecificity of the reaction strongly depends on substituent X: at C-6 for X = H, CONH₂, C₆H₅ and at C-2 for X = CH₃. 3-Aminocarbonyl-1-t-butylpyridinium iodide ( 5 ) on treatment with liquid ammonia/potassium permanganate exclusively gives the 4-imino compound 8 ; ¹H nmr spectroscopy shows that 5 in liquid ammonia gives a mixture of the σ-adducts 4-amino-1,4-dihydro- and 6-amino-1,6-dihydro-3-pyridinecarbonamide ( 6 and 7 ). Surprisingly, an oxodemethylation reaction is observed on treatment of 3-aminocarbonyl-1,6-dimethylpyridinium iodide ( 13 ) with liquid ammonia/potassium permanganate, 1,6-dihydro-1-methyl-6-oxo-3-pyridinecarboxamide ( 14 ) being obtained. This compound can easily be converted by phosphorus oxychloride into the alkaloid nudiflorine ( 15 ).     

Ligand isotope studies of Zeise's salt derivatives (and their CO analogues) with some aza-heterocycles and their N-oxides. II : Their preparation,characterisation, and use in developing 1H nmr and infrared spectra as a diagnostic tool

Forty-one π-acid complexes of the type cis-[Pt(bipyO₂H)(A)X₂]X and trans-[PtL(A)X₂] (A = C₂H₄, CO; X = Cl, Br; L = pyridazine {pdz}, pyrazine N-oxide {pzO}, quinoline {quin}, quinoline N-oxide {quinO}, 2,2′-bipyridine {bipy}, 1,10-phenanthroline {phen}) and their deuterated L and C₂D₄ analogues have been characterised employing infrared and ¹H nmr spectroscopy. The employment of v₁₂ (CH₂ scissors ∼1460 cm⁻¹) of η²-ethene as a diagnostic probe in distinguishing between 4- and 5-coordination is proposed, while the summed percentage decrease of v₂+v₃ (vC=C/δCH₂) may be used to distinguish between N- and O-coordination. The use of chemical shifts (¹H nmr spectroscopy) is confirmed as a suitable means to distinguish between 4- and 5-coordination and is also shown to be suitable for distinction between N- and O-coordination in four coordinate Pt(II) η²-ethene complexes. In contradiction of previous reports, it is found that J_Pt-H cannot be employed to determine the coordination number.     

STUDIES OF PHOSPHAZENES. PART VI.1 THE PREPARATION OF THE ISOMERIC TETRACHLOROBIS-ISOPROPYLAMINOCYCLOTRIPHOSPHAZATRIENES

Abstract

The three isomers of N₃P₃Cl₄(NHPr¹)₂ have been prepared and separated by gas-liquid chromatography. Their structures have been assigned on the basis of ¹H and ³¹P nmr data.     

Synthesis and isolation of iodocarbazoles. Direct iodination reaction of N‐substituted carbazoles

Iododerivatives of N‐methylcarbazole ( 1 ), N‐phenylcarbazole ( 2 ), N‐benzylcarbazole ( 3 ), 2‐methoxy‐N‐methylcarbazole ( 4 ) and 3‐acetamido‐N‐ethylcarbazole ( 5 ) are synthesised. N‐Iodosuccinimide (NIS) in tetrahydrofurane/H₂SO₄ (catalyst), a mixture of KIO₃ ‐ KI ‐ H₂SO₄ (catalyst) in ethanol and a mixture of KIO₃ ‐ KI in glacial AcOH as iodinating agents have been used and their uses have been compared. The preparation, isolation and characterization of compounds 1a, 1b, 1c, 1d, 2a, 2b, 3a, 3b, 4a, 4b, 4c and 5a are reported (mp, t_R, R_f, ¹H‐nmr, ¹³C‐nmr, IR and ms). All of them are described for the first time except 3,6‐diiodo‐N‐phenyl‐carbazole ( 2b ). Semiempirical PM3 calculations have been performed to predict reactivity of N‐substituted carbazoles and their iododerivatives. Theoretical and experimental results are discussed briefly.     

Synthesis and NMR studies of thiazolidine-4-carboxylic acid derivatives containing a nitro ester function

The preparation of thiazolidine-4-carboxylic acid derivatives containing a 2-nitrooxyethylamine group, potentially active as vasodilators, is reported. Their ¹H nmr studies carried out to establish the configuration of the C2 stereocenter and the full assignment of their ¹H and ¹³C nmr spectra, are also reported.     

Identification of some isomeric 3,5-unsymmetrically substituted 1-aroyl-pyrazole derivatives by NMR spectroscopy

The ¹H and ¹³C nmr chemical shifts are used for the structural assignment of isomeric 1-aroyl-4,5-dihydro-5-hydroxy-4,4-dimethyl-1H-pyrazoles 1 unsymmetrically substituted with phenyl or methyl in the 3,5-positions of the pyrazole ring. The ¹H nmr spectra of 1-aroyl- or 1-acetyl-4-methyl-1H-pyrazoles 2 are useful in structure elucidation of unsymmetrically 3- or 5-methyl substituted derivatives.     

Synthesis of some oxadiazole derivatives of d-mannose

The syntheses of 2-methyl-5-[1′,2′,3′,4′,5′-penta-O-benzoyl-D-manno-pentitol-1′-yl]-1,3,4-oxadiazole and 5-methyl-3-[1′,2′,3′,4′,5′-penta-O-benzoyl-D-manno-pentitol-1-′yl]-1,2,4-oxadiazole, as well as their intermediate products, are described. Their ¹H and ¹³C nmr and ms spectra are presented and their preferential conformation in solution are proposed.     

Annelated derivatives of 2-phenylquinoline, 2-(2′-pyridyl)quinoline and 2-phenyl-1,8-naphthyridine

Annelated derivatives of 2-phenylquinoline, 2-(2′-pyridyl)quinoline, and 2-phenyl-1,8-naphthyridine have been prepared where the bridging unit contains from one to four methylene units. The conformational properties of these molecules have been analyzed by ¹H nmr and uv spectroscopy as well as by pK_a determinations.