Synthesis,purification and spectroscopic characterization of potential impurities of hexamethylmelamine

The syntheses and spectroscopic properties (ir, ¹H nmr, ¹³C nmr, uv and ms) of pure samples of 2-chloro-4,6-bis(dimethylamino)-s-triazine 1 , 4,6-dichloro-2-dimethylamino-s-triazine 2 , 4,6-bis(dimethylamino)-s-triazin-2(lH)-one 3 , 4-chloro-6-dimethylamino-s-triazin-2(1H)-one 4 , 6-dimethylamino-s-triazine-2,4(1H,3H)-dione 5 , and 2,4,6-tris(dimethylamino)-s-triazine (altretamine, HMM) are reported. Evidence for enol-keto equilibria are also presented for 3 , in which the enol form exhibits as an H-bonded dimer structure similar to the dimer of organic carboxylic acids.     

A comparison of crystallographic and NMR data for thieno[2,3‐b:4,5‐b′]dipyridine and its monohydroperchlorate salt

X‐ray crystallographic studies of thieno[2,3‐b:4,5‐b′]dipyridine ( 1 ) and its monohydroperchlorate salt ( 1a ) show that 1 is protonated at N1 in ring A and not at N6 in ring C. In each compound individual rings are planar, but there is a small dihedral angle‐of‐twist between the A and C rings. On going from 1 to 1a the largest changes in bond angles and bond lengths occur in ring A. ¹H and ^l3C nmr spectra of 1 plus the ¹³C nmr spectrum of 1a are reported.     

Structure analysis of some α‐(n‐methyl‐n‐formylaminomethyl)‐quinolines

The ¹H and ¹³C nmr spectra of the rotational isomers 3a and 3b of 6‐N‐methyl‐N‐formylaminomefhyl)‐thioquinanthrene were completely assigned with a combination of 1D and 2D nmr techniques. The key‐parts of this methodology were long‐range proton‐carbon correlations and NOE experiments with N‐methyl‐N‐formylaminomethyl substituent. The X‐ray study of 4‐methyl‐2‐N‐methyl‐N‐formylaminomethyl)quinoline 4a as well as ¹H and ¹³C nmr spectra show that N‐methyl‐N‐formylaminomethyl substituent in 4a and 4b has a different steric arrangement than the same substituent in 3a and 3b .     

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.     

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.     

Synthesis and molecular structure of novel 4‐aryloctahydropyrido‐[1,2‐c]pyrimidine derivatives

A series of new 4‐aryloctahydropyrido[1,2‐c]pyrimidine‐1,3‐diones 6a,b,d‐h and j were synthesized by intramolecular cyclization of α‐aryl‐α‐(1‐ethoxycarbonyl‐2‐piperidyl)‐acetamide derivatives 5a,b,d‐h and j . The structures of compounds were determined by ¹H and ¹³C nmr spectroscopy. Nmr and X‐ray diffraction data indicate that the configuration at the C4, C4a stereocenters constitute RR and SS pair.     

Eight-membered heterocycles. 12H-dibenzo[d,g][1,3,2]dioxaphosphocin and 12H-dibenzo[d,g][1,3,2]dioxaborocin derivatives

The synthesis of phosphonite and thiophosphite derivatives of the 12H-dibenzo[d,g][1,3,2]dioxaphosphocin ring system is described. The 'H nmr shows evidence for long-range coupling of the C-12 methine proton to phosphorus. The ¹H nmr of the 12H-dibenzo[d,g][1,3,2]dioxaborocin ring system is compared to that of the phosphorus analog. The nmr spectral data suggest that the phosphorus and boron containing ring systems have similar ring conformations.     

Synthesis and spectral properties of 2‐[(o‐ and p‐substituted)aminophenyl] ‐3H‐5‐[(o‐ and p‐substituted)phenyl]‐7‐chloro‐1,4‐benzodiazepines

A series of twelve new 2‐[(o‐ and p‐substituted)aminophenyl]‐3H‐5‐[(o‐ and p‐substituted)phenyl]‐7‐chloro‐1,4‐benzodiazepines, which have possible pharmacological properties has been obtained. The synthesis was carried out following six steps. The structure of all products was corroborated by ir, ¹H nmr, ¹³C nmr and ms. In addition for the compound 2‐(o‐chloroaminophenyl)‐3H‐5‐(o‐fluorophenyl)‐7‐chloro‐1,4‐benzodiazepine 7, its structure was confirmed by X‐ray diffraction.     

Synthesis, 1H, 13C-NMR and mass spectral study of aryloxyquinuclidinium salts

A series of 3 -aryl -3 -hydroxy-N -(4 ′-aryloxobutyl)quinuclidinium salts have been synthesized. The ¹H nmr, ¹³C nmr and mass spectra of these compounds are described and discussed.     

Synthesis,structural and conformational study of 6-hydroxy (or acyloxy) derivatives of the 1,3-dimethyl-1,3-diazoniatricyclo[3.3.1.13–7]decane system

1,3-Dimethyl-1,3-diazoniatricyclo[3.3.1.1^3–7]decan-6-ol, and his p-chlorobenzoxy and diphenylacetoxy derivatives have been synthesized and studied by ¹H and ¹³C nmr spectroscopy. The crystal structure of the alcohol 2a has been determined by X-ray diffraction. Each ring of the adamantane cage system is a nearly perfect chair. From the ¹H and ¹³C nmr data, several stereoelectronic effects have been deduced.     

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.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 10. Synthesis and structure determination of naphtho[1′,2′:4,5]thieno[3,2-a]-4,7-phenanthroline

Naphtho[1′,2′:4,5]thieno[3,2-a]-4,7-phenanthroline, a novel hexacyclic ring system has been synthesized in four steps. The ¹H and ¹³C nmr assignments have been made using two-dimensional nmr techniques. The tertiary helical structure was determined by X-ray crystallographic analysis.     

Synthesis of s-triazolo[4,3-b]pyridazine C-nucleosides

A one step synthesis of s-triazolo[4,3-b]pyridazine using 3-chloro-6-hydrazinopyridazine and an appropriate thioformimidate is described. Applying this procedure to 5-O-benzoyl-1-benzylthio-1-formimidate-D-ribofuranose, 5′ benzoyl-6-chloro-3β-D-ribofuranosyl-s-triazolo[4,3-b]pyridazine was obtained. Substitutions of chlorine by nucleophilic reagents afforded some derivatives of a new series of C-nucleo-sides. Structural determination including anomeric configuration assignment is discussed based mainly on ¹H nmr spectroscopy.     

Complete spectroscopic structural characterization of novobiocin,isonovobiocin, decarbamylnovobiocin, 2″-(o-Carbamyl)novobiocin,and novobiocin-2″,3″-carbonate

The rigorous structural characterization of novobiocin, is reported using mass spectrometric, infrared and nmr spectroscopic analysis. Complete nmr assignments are reported. Previous reports in the literature had left some quaternary carbon resonances unassigned. Isonovobiocin and decarbamylnovobiocin, although known in the literature for a number of years, have never been completely characterized. Mass spectrometric fragmentation pathways and complete ¹H and ¹³C nmr assignments are reported for these congeners for the first time. The mass spectral fragmentation pathway and nmr assignments are also reported for 2″-(O-carbamyl)novobiocin although the nmr assignments at lower field were reported previously. The structural characterization of novobiocin-2″,3″-carbonate observed in the Test Assay procedure used for Novobiocin is reported for the first time.     

Nitrogen bridgehead compounds. Part X (1). 1H and 13C nmr study of pyrido[1,2-a]pyrimidines

By ¹H nmr, the predominance of the conformer with a quasi-axial 6-methyl group was established for the pyrido[1,2-a]pyrimidines I-III. The ¹³C nmr spectra of I-III were completely assigned. The conjugative effect of substitution at G-3 on ¹H and ¹³C chemical shifts of the C-9 methylene group parallels its effect on reactivity.     

Synthesis of 3-(6-alkylaminopurin-9-yl)-2,3-dideoxy-D-thero-pentopyranoses and their reduction to 3-(6-alkylaminopurin-9-yl)-2,3-dideoxy-D-thero-pentitols

3-(6-Alkylaminopurin-9-yl)-2,3-dideoxy-D-threo-pentopyranoses 3 were prepared by condensation of unprotected 2-deoxy-D-ribose (2) with N⁶-alkyladenines 1 in a phosphorus pentoxide reagent mixture. Reduction of the pentoses 3 gave the corresponding 3-(6-alkylaminopurin-9-yl)-2,3-dideoxy-D-threo-pentitols 4. The structures of 3 and 4 were determined by ¹³C nmr, ¹H nmr and 2D ¹H nmr (COSY).     

Synthesis,structural and conformational study of 4-α-(or β)-p-chlorobenzoyloxy-1-azaadamantane hydrochloride

4-α-(or β)-p-Chlorobenzoyloxy-1-azaadamantane hydrochloride have been synthesized and studied by ¹H and ¹³C nmr spectroscopy, and the crystal structure of the α-epimer has been determined by X-ray diffraction. Each ring of the adamantane cage system is a nearly perfect chair, the substituted cyclohexane and piperidine rings, in endo and exo position respectively, having the biggest deviation. From the ¹H and ¹³C nmr data, several stereoelectronic effects have been deduced.     

A highly selective hydrogen-deuterium exchange in indolium heptamethine cyanines

Chemical shift assignments in ¹H nmr spectra of four tricarbocyanines have been made. Studies by ¹H nmr have shown a rapid acid-catalyzed proton exchange at positions 1′,7′ and a much slower exchange at positions 3′,5′ of the heptamethine chain. Base catalysis results in a slow exchange at positions 1′,7′ only.     

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.     

Dipolar additions with 1-(4,6-dimethylpyrimidin-2-yl)- and 1-(4,6-dimethoxy-s-triazin-2-yl)-3-oxidopyridinium betaines

Cycloaddition to 1-(4,6-dimethylpyrimidin-2-yl)- and 1-(4,6-dimethoxy-s-triazin-2-yl)-3-oxidopyridinium betaines across the 2,6-positions of the pyridine rings with indene, acenaphthylene and ethyl cinnamate gave substituted 8-aza[3.2.1]bicycIooct-3-en-2-ones, whereas the [6π + 4π] cycloaddition reaction with 6,6-dimethylfulvene gave a tricyclo[6.3.1.0^2.6]dodeca-2,(6),4,9-trien-11-one. Structural and configurational assignments of the cycloadducts were deduced from ¹H nmr and ir spectral data.