112,025 research outputs found
Tautomerism and hydrogen bonding in reaction products from 4-aminopent-3-en-2-one and diazonium ions
No full textThe azo-coupling products have been prepared from 4-aminopent-3-en-2-one and 4-chloro- or 4-nitrobenzenediazonium ion.
Structure of the products obtained was studied by means of multinuclear NMR spectroscopy in CDCl3 solutions and X-ray
diffraction in solid state. Both products are predominantly present as azo forms in both the solution and the solid state, the azo
form content being higher in solid state. The substituent effect on azo-hydrazone tautomeric equilibrium of the substances is
more significant in solution than in solid state
Hydantoins and thiohydantoins derived from 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid
No full textThe reaction of methyl (S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate with isocyanates (phenyl, naphthalen-1-yl, cyclohexyl, (S)-1-methylbenzyl) in ether has been used to prepare N-substituted methyl (3S)-2-aminocarbonyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylates. These compounds were cyclised by action of CF3COOH to give the corresponding 2-substituted (10aS)-10,10a-dihydroimidazo[1,5-b]isoquinoline-1,3(2H,5H)-diones (hydantoins Tic-H). Hydantoins Tic-H were also prepared by the reaction of methyl (S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate with isocyanates (methyl, (1S)-1-methylbenzyl, 4-methylphenyl, 3-methylphenyl, 4-chlorophenyl, 2,4-dichlorophenyl, 4-methoxyphenyl, 5-chloro-2-methoxyphenyl, 3-chloro-4-ethoxyphenyl) and triethylamine in CH2Cl2. 2-Substituted (10aS)-3-thioxo-1,2,3,5,10,10a-hexahydroimidazo[1,5-b]isoquinolin-1-ones (thiohydantoins Tic-TH) were prepared analogously by the reaction of methyl (S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate with isothiocyanates (methyl, ethyl, allyl, phenyl). The optical purity of selected substances was determined chromatographically
Structure and reactivity of 3,3-disubstituted 1-(5-nitro-2,1-benzisothiazol-3-yl)triazenes
No full textThe reaction between 5-nitro-2,1-benzisothiazole-3-di-
azonium species and N-substituted anilines produces the 1-
(5-nitro-2,1-benzisothiazol-3-yl)-3,3-disubstituted triazenes
1. These triazenes are highly stable, and even in strongly
acidic medium (0.5 molL−1 H2SO4) they are only slowly de-
composed back to the diazonium ion and substituted anilin-
ium ion (for the N-ethyl derivative in 0.5 mol·L−1 H2SO4 at
25 °C, t1/2 7 h). A series of six triazenes were characterised
by their 1H and 13C NMR spectra and mass spectra. Two of
the triazenes were also identified by X-ray crystallography
Solution and solid state structure and tautomerism of azo coupled enaminone derivatives of benzoylacetone
No full textThe reaction of 4-substituted benzenediazonium tetrafluoroborates with 3-amino-1-phenylbut-2-en-1-one, 4-amino-4-phenylbut-3-en-2-one and their N-aryl derivatives 1a-1g has been used to prepare the respective azo coupling products i.e. compounds 2-5 from enaminone 1a, compounds 6-9 from enaminone 1c, compound 10 from enaminone 1d, compound 11 from enaminone 1e, compounds 12, 13 from enaminone 1f, compounds 14, 15 from enaminone 1b and compound 16 from enaminone 1g. Tautomerism of the azo coupling products prepared has been investigated in CDCl3 solutions by means of H-1, C-13 and N-15 NMR spectra. Crystal structures of selected products have also been investigated by means of X-ray diffraction
Synthesis, NMR and X-ray characterisation of 6-substituted 4-amino-5-aryldiazenyl-1-arylpyridazinium salts
No full textA new simple method has been used to prepare 6-substituted 4-(subst. amino)-5-aryldiazenyl-l-arylpyridazinium salts from N-methyl- or N-aryl-3-amino-l-phenylbut-2-en-l-ones and 4-aminopent-3-en-2-ones and substituted benzenediazonium tetrafluoroborates or hexafluorophosphates. The structure of selected derivatives was studied by means of N-15 NMR spectra and X-ray
Formation of pyridazinium salts by azo coupling of N-substituted 3-amino-1-phenylbut-2-en-1-ones and diazonium salts
No full textTreatment of 3-(2,4-dimethoxyphenylamino)- and 3-methylamino-1-phenylbut-2-en-1-ones with some benzenediazonium tetrafluoroborates gives, besides the usual azo coupling products [i.e., 3-(substituted imino)-1-phenylbutane-1,2-di-ones 2- (4-substituted phenylhydrazones) and 2-(4-methoxy-phenyldiazenyl)-3-methylamino-1-phenylbut-2-en-1-one, respectively], the previously unreported 1,4,5,6-tetrasubstituted pyridazinium tetrafluoroborates. The pyridazinium salts have been identified by X-ray analysis and by their H-1, C-13, N-15, B-11 and F-19 NMR spectra. Their formation is most probably the result of nucleophilic attack on the carbonyl carbon by the nitrogen of the hydrazone group and subsequent dehydration
An NMR and X-ray study of the structure of the azo coupling product of 4-dimethylaminopent-3-en-2-one and benzenediazonium-tetrafluoroborate
No full text4-Dimethylaminopent-3-en-2-one reacts with two molecules of benzenediazonium-tetrafluoroborate to give compound 1. The structure of this compound was determined by means of X-ray analysis of its crystal and 1H, 13C and 15N NMR spectra of its solution in CDCl3. The molecule of this compound contains one azo group and one hydrazone group. The substance exists, both in crystal form and in solutions of concentrations above 0.1
mol-1, in the form of a dimer, in which the pair of molecules are bound by two hydrogen bonds N–H ... N. On diluting the
solution, the dimers decompose, the two forms being in an equilibrium that is rapid on the NMR time scale
Novel 5-(4-substituted-phenyldiazenyl)-1,3,2 lambda(4)-oxazaborines and their rearrangement to 1,2,4,3 lambda(4)-triazaborines
No full textThe reaction of substituted benzenediazonium tetraphenylborates with the beta-enaminones derived from pentane-2,4-dione, 1-phenylbutane-1,3-dione, and 1,4-diphenylbutane-1,3-dione with a primary or secondary (N-methyl, N-phenyl) amino group in CH2Cl2 gives 5-(substituted-phenyldiazenyl)-2,2-diphenyl-4,6-disubstituted- 1,3,2 lambda(4)-oxazaborines or 5-(substituted-phenyldiazenyl)-2,2-diphenyl-3,4,6-trisubstituted-1,3,2 lambda(4)- oxazaborines, respectively. The reaction intermediate of these compounds has been identified, and a mechanism for the reaction has been suggested. Substituted 1,3,2 lambda(4)-oxazaborines gradually rearrange into 1,2,4,3 lambda(4)-triazaborines at temperatures above 100 degrees C
Structure and base catalysed cyclization of methyl (2,6-disubstituted-4-nitrophenylsulphanyl)ethanoates
No full textThe conformation of side chain –SCH2COOCH3 in title compounds in crystal agrees with the reactivity of these compounds
in base catalysed ring closure in solution. In the 2,4-dinitro derivative, the side chain is oriented towards the unsubstituted
ortho-position of benzene ring, in the case of the 2-methoxycarbonyl derivative towards this substituent
Derivatives of 1,2,3,4-Tetrahydroisoquinoline-3-carboxylic Acid
No full textThe following derivatives of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid have been prepared in their (S)-form and as racemates: hydrochloride of methyl ester, N-carboxy anhydride, and N-acetyl derivative. All the substances were fully characterised by elemental analyses, H-1 and C-13 NMR spectra, and optical rotation, as the case may be; the M-carboxy anhydride was also characterised by means of X-Ray diffraction. Also identified was the intermediate of the reaction of the title acid with phosgene, the N-chlorocarbonyl derivative, and the respective methyl ester was prepared. The dioxopiperazine of the title acid was prepared and characterised both in pure (S,S)-form and in the form of a mixture of two racemates. The optically pure dioxopiperazine was prepared by a reaction of the N-carboxy anhydride in solid phase
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