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    Union Catalogue of Agricultural Libraries in the Netherlands

    The WUR Library Catalogue contains bibliographic data on books and periodicals held by the libraries of Wageningen University and Research Centre and some 15 associated libraries. Holding data are added to each record.

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Record number 104678
Title Ring transformations in reactions of pyrimidine and N-alkylpyrimidinium salts with nucleophile
show extra info.
[door] E.A. Oostveen
Author(s) Oostveen, E.A.
Publisher Wageningen : Pudoc
Publication year 1977
Description 58 p.
Notes Proefschrift Wageningen
Tutors Plas, Prof. Dr. H.C. van der
Graduation date 1977-06-08
Dissertation no. 690
Author abstract show abstract

Paper I

On treatment with liquid ammonia at -33°C, the quaternary pyrimidinium salts, i.e. 1-methylpyrimidinium methyl sulfate, 1,2-dimethylpyrimidinium iodide, 1,4,6-trimethyl-pyrimidinium iodide and 1,2,4,6-tetramethylpyrimidinium iodide demethylate yielding pyrimidine. 2-methyl-, 4,6-dimethyl- and 2,4.6-trimethylpyrimidine, respectively. It was observed that under these conditions 1-methyl-[1,3- 15N]-pyriniidiniuni methyl sulfate yields [1- 15N]-pyrimidine. By measuring the PMR spectra of above- mentioned pyrimidinium salts in liquid ammonia it is shown that these salts undergo covalent amination on the 1,6-azomethin bond. These results indicate that the demethylation reaction occurs via an Addition-NucleophileRing-Opening-Ring Closure mechanism.

Paper II

On treatment with active methylene compounds in basic media the quaternary pyrimidinium salts, i.e. methyl 1-methylpyrimidinium sulfate, 1-methyl-4-phenylpyrimidinium iodide and 1-methyl-5- phenylpyrimidinium iodide are converted into pyridine derivatives. The mechanism of the reaction is discussed.

Paper III

On treatment of the quaternary pyrimidinium salts i.e. 1-methyl-4-phenylpyrimidinium iodide and 1-methyl-5-phenylpyrimidinium iodide with cyanamide, O -methylisouronium chloride or bis[S-methylisothiouronium] sulfate in basic media, 2-amino-4-phenylpyrimidine and 2-amino-5-phenylpyrimidine are formed respectively. A ring transformation is involved in which the two-atom fragment N(1)-C(2) of the pyrimidine ring is replaced by an N-C fragment of the reagent. On reacting 1-methylpyrimidinium iodide with benzamidinium chloride or pivalamidinium chloride in a solution of sodium ethoxide in ethanol, 2-phenylpyrimidine and 2- tert -butylpyrimidine are formed respectively.

It is proved by 15N-labelling that this nucleophilic substitution occurs via a ring transformation in which the N(1)- C(2)-N(3) fragment of the pyrimidine is replaced by the N-C-N fragment of the amidine. These reactions are new examples of a nucleophilic substitution occurring according to an S N (ANRORC) mechanism.

Paper IV

Reaction of 4-alkoxy- or 4,6-dialkoxypyrimidines with 1 equivalent of triethyloxonium tetrafluoroborate yields 4-alkoxy-N-ethyl or 4,6-dialkoxy-N-ethylpyrimidinium salts, respectively. With two or more equivalents of this reagent, rearrangement of N-ethyl-alkoxypyrimidinium salts into 1-ethyl-3-alkyl-1,4(3,4)-dihydro-4-oxopyrimidinium salts takes place. These rearrangements can also be performed by heating. The mechanism of these rearrangement reactions is discussed.

Paper V

The crystal and molecular structures of two isomeric compounds, 1-ethyl-4,6-diethoxypyrimidinium tetrafluoroborate and 1,3-diethyl-1,4(3,4)-dihydro-6-ethoxy-4-oxopyrimidinium tetrafluoroborate, reaction products of 4,6-diethoxypyrimidine with Meerwein reagent [O(C 2 H 5 )3+BF4-] , have been determined by means of X-ray diffraction.
1-Ethyl-4,6-diethoxypyrimidinium tetrafluoroborate is monoclinic a=10.794, b=13.361,c=10.892 Å,  β =112.6°, space group P2 1 /n, four molecules per unit cell.
1,3-Diethyl-1,4(3,4)-dihydro-6-ethoxy-4-oxopyrimidinium tetrafluoroborate is monoclinic, a=17.637, b=14.054, c=11.501 Å,  β =101.7°, space group C2/c, eight molecules per unit cell.
In both structures the fluoroborate ions are disordered. The bond distances in the π-electron systems are reasonably well described in terms of a small number of resonance structures.

Paper VI

Treatment of 1,3-diethyl-1,4(3,4)-dihydro-4-oxopyrimidinium tetrafluoroborate and its 2-phenyl, 6-phenyl, 6-methyl and 6-ethoxy derivatives with aqueous ammonia resulted in the formation of a mixture of open-chain compounds i.e. N -formyl(acetyl,benzoyl)- N -ethyl-3-(ethylamino)acrylamides and N -ethyl-3-[formyl(acetyl,benzoyl)ethylamino]-acrylamides. They are formed by cleavage of the pyrimidine ring between the N(1)-C(2) and N(3)-C(2) bond, respectively. In liquid ammonia the same ring cleavage generally occurs; however, in the case where a 6-ethoxy group is present, recyclisation can take place, leading to 6-(ethylamino)pyrimidine derivatives. This degenerate ring transformation has been observed also with the 2-methyl and 2-phenyl derivative of 1,3-diethyl-1,4(3,4)-dihydro-6-ethoxy-4-oxopyrimidinium tetrafluoroborate. Evidence is presented by means of  1H-NMR and 13C-NMR spectroscopy that all these reactions are iniated by attack of NH 3 at the C(2)-position. Some of the above-mentioned open-chain compounds underwent a ring closure to the initially used 1,3-diethyl-1,4(3,4)-dihydro-4-oxopyrimidinium tetrafluoroborates on treating them with hydrofluoroboric acid in absolute ethanol.

Paper VII

On treatment with liquid ammonia at -33° the quaternary pyrimidinium salts i.e. 4-ethoxy-1-ethyl- and 4,6-diethoxy-1-ethylpyrimidinium tetrafluoroborate undergo amino-de-ethoxylation, yielding 1,4-dihydro-1-ethyl-4-iminopyrimidine hydrogen tetrafluoroborate and a mixture of 1,4-dihydro-6-ethoxy-1-ethyl-4-imino-  and 1,6-dihydro-4-ethoxy-1-ethyl-6-iminopyrimidine hydrogen tetrafluoroberate, respectively. 1H-NMR and 13C-NMR spectroscopic evidence is presented for the fact that compounds 1 and 3 easily give σ-adducts at position 2. Using 15N-labelled ammonia it was shown that in these amino-de-ethoxylation reactions the substitution at C(4) or C(6) does not involve ring opening but probably occurs via an S N (AE n ) process. Reaction of 4-ethoxy-1-ethyl-2-phenyl-, 6-ethoxy-1-ethyl-4-phenyl-, 4,6-dimethoxy-1-ethyl-2-phenyl- and 4,6-dimethoxy-1-ethyl-2-methylpyrimidinium tetrafluoroborate with liquid ammonia gives besides the amino-de-ethoxylation product degenerate ring transformations leading to the N-deethylated products 14-16 and 4(6)-ethylaminopyrimidines 17-19. The salt 11 and 1,6-dihydro-1-ethyl-6-imino-4-phenylpyrimidine hydrogen tetrafluoroborate undergo, with potassium hydroxide, a Dimroth rearrangement to pyrimidines 20 and 17, respectively.

Paper VIII

The mechanism of the conversion of pyrimidine into 5-ethyl-2-methylpyridine has been investigated. It has been proved, using the labelled compounds [1,3- 15N]pyrimidine, [4,6- 14C]pyrimidine and [5- 14C]pyrimidine, that this reaction proceeds via a mechanism, in which the pyrimidine ring is fragmentated into two molecules of HCN and one molecule of N -methylacetaldimine. Four molecules of this imine undergo an aldol type condensation leading to 5-ethyl-2-methylpyridine.

Online full textINTERNET
On paper FORUM ; STACKS ; NN08200,690
FORUM ; STACKS ; NN08202,690
Keyword(s) (cab) pyrimidines / chemical reactions
Categories Organic Chemistry
Publication type PhD thesis
Language English
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