Dihydro pyrimidones

Fig. 3. Photochemical transformation, on irradiation at 254 nm in 0.01 M phosphate buffer pH 7.1, of 6,6 -f>M-(l-methyl-3,6-dihydro-pyrimidone-2) with regeneration of l-methylpyrimidone-2. The curve marked o is that for the initial reduction product numbers beside other curves are times of irradiation in min.

SYN S 2,3-DIHYDRO-6-PROPYL-2-THIOXO-4(lH)-PYREvIIDINONE 2-MERCAPTO-4-mT)ROXY-6-N-PROPYLPYRIMIDINE 2-MERCAPTO-6-PROPM.-4-PYRIMIDONE 2-MERCAPTO-6-PROPYLPYRIMID-4-ONE PROCASIL PROPACIL PROPILTHIOURACIL... 

The electrophor of derivatives of 2-aryl-5,6-dihydro-4-pyrimidone is similar to that of benzamidine and the reduction of the azomethine group is observed. The product, a geminal amine, may be hydrolyzed with loss of an arylaldehyde [401]. 

Each of the diazines can be constructed from an appropriate source of two nitrogens and a dicarbonyl compound. In the case of pyridazines, the nitrogen source is, of course, hydrazine and this in combination with 1,4-dicarbonyl compounds readily produces dihydro-pyridazines, which are very easily dehydrogenated to the aromatic heterocycle. Pyrimidines result from the interaction of a 1,3-dicarbonyl component and an amidine (as shown) or a urea (giving 2-pyrimidones) or a guanidine (giving 2-amino-pyrimidines), without the requirement for an oxidation step. 

The addition of ketene to amidines (1,3-diazadienes) leads to [4 - - 2] cycloaddirion to form 5,6-dihydro-4-pyrimidones. When diazabutadienes 360 are employed as the diene constituent, either [2 + 2] 361 or [4 + 2]... 

A soln. of dimethyloxosulfonium 1,4-dihydro-1-(2,3-0-isopropyIidene-/ -D-ribo-furanosyl)-4-oxo-2-pyrimidinemethylide in aq. 50%-ethanol treated 10 min. at room temp, with active Raney-Ni l-(2,3-0-isopropylidene-/ -D-ribofuranosyl)-2-methyl-4(lH)-pyrimidone. Y 95%. F. e., also by photoreduction with NaBH4, s. T. Kunieda and B. Witkop, Am. Soc. 93, 3487 (1971). 

Mobinikhaledi et al., in 2007, achieved the synthesis of 3-oxo-2-[(Z)-l-phenylmethylidene]-5H-[l,3]thiazolo[3,2-a] pyrimidine derivatives 14 (Scheme 5) in good yields by the reaction of an appropriate 3,4-dihydro-2(H)-pyrimidone 13, chloroacetic acid, sodium acetate and benzaldehyde [23],... 

Aryl/alkyl-3, 4-dihydro-2(lH)-pyrimidone esters and 5-acetyl-4-aryl/alkyl-6-methyl-3,4-dihydropyrimidin-2(l)-ones were prepared under microwave radiations efficiently using montmorillonite clay-Cu(N03)2.2.5H20 system (Sitha et al., 2010). The reaction rate was enhanced in presence of microwave irradiation... 

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