Summary. Proton-NMR. spectra of amino-and hydroxypyrimidines including biologically important bases have been measured in four solvents : CF,COOH, CF,COOH-SO,, FSO,H and FSO,H-SbF5-SO, a t 27" and -55°C. In CF,COOH mono-cations are formed, whereas in FSO,H and FSO,H-SbF5-SO, double protonation occurs. I n each case the structures of the protonated species are derived from the chemical shifts of CH, NH and OH protons and proton-proton spin coupling constants. A combination of the measurements described leads to a complete assignment of all proton resonances of the protonated pyrimidines. This approach is also recommended for the structural determination of heterocyclic compounds. Die hier aufgefiihrten Forineln fur die Neutralmolekeln konnen auf Grund der bisherigen Studien 2, iiber die Tautomerie substituierter Pyrimidine als die vorherrschenden tautomeren Strukturen betrachtet werden.
In fruheren Mitteilungen1. Pyrimidin (1). Die Spektren des Grundkorpers in den vier Losungsmitteln sind in Fig. 1 a-f (1)
Methylenaktive Ketone 2 kondensieren mit den vinylogen Amidacetalen und Aminalestern 1 a, b oder rnit den vinylogen hmidiniumsalzen 8 und Natriummethylat zu substituierten 5-(Dimethylamino)pentadienonen 3a-m, 4a, Sa-d und 6a-c, entsprechend rnit 9 zu Heptatrienonen 10af. Erhitzen von 10a-f fiihrt unter RingschluB und Dimethylaminabspaltung zu den Phenylketonen 14a-f. Die Kinetik der elektrocyclischen Reaktion von 10a zu 14a wurde gemessen. Aus den Verbindungen 3a-m, 4a, 5a-b, 6a gewonnene Polymethiniumsalze 22a-m, 23a-25b und 27 werden rnit Ammoniakl Ammoniumchlorid oder in einer Ammonacetatschmelze zu den Pyridinen 29a-m, 30a-32b und 33 cyclisiert. Aus 33 kann das neue Pseudoazulen 35 gewonnen werden.
Reaction of Vinylogous Formamidinium Salts with Nucleophiles, 11. -Polymethinium Salts from Methylene-Active KetonesThe rnethylene-active ketones 2 condense with the vinylogous amide acetales and aminal esters 1 a, b or with the vinylogous amidinium salts 8 in the presence of sodium methoxide to give substituted 5-(dimethy1amino)pentadienones 3a-m, 4a, 5ad and 6a-c ; analogously, condensation with 9 affords the heptatrienones 10a-f. Heating of 1Oa-f leads, via ring closure and elimination of dimethylamine, to the phenyl ketones 14a-f. Rates and kinetics for the electrocyclic transformation of 10a into 14a were measured. The polymethinium salts 22a-m, 23a-2Sb and 27 formed from compounds 3a-m, 4a, 5a-b and 6a cyclize on treatment with ammonia/ammonium chloride or with molten ammonium acetate to the pyridines 29a--m, 30a-32b and 33. The new pseudoazulene 35 can be prepared from 33.In einer vorhergehenden Mitteilungl) haben wir gezeigt, daB vinyloge Formamidiniumsalze 8 Ausgangsverbindungen zur Synthese von Pyrimidinen sind In der vorliegenden Arbeit wird ein einfacher Weg zu neuartigen, meist hochsubstituierten Polymethiniumsalzen, Polyenonen und deren Folgereaktionen beschrieben 2). *) Korrespondenz bitte an diesen Autor richten.
Proton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF3COOH, FSO3H and FSO3HSbF5SO2 at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono‐, di‐ and tri‐cations are described and fully assigned.
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