Three Component Reaction: An Efficient Synthesis and Reactions of 3,4-Dihydropyrimidin-2(1H)-Ones and Thiones Using New Natural Catalyst

Abstract

Synthesis of 3,4-dihydropyrimidin-2(1H)-one and 3,4-dihydropyrimidin-2(1H)-thione derivatives from aldehydes, 1,3-dicarbonyl derivatives and urea or thiourea using granite and quartz as new, natural and reusable catalysts. Some of the 3,4-dihydropyrimidin-2(1H)-thione derivatives were used to prepare new heterocyclic compounds. The antimicrobial activity of selected examples of the synthesized compounds was tested and showed moderate activity.

<strong>Synthesis and characterization of 2-arylidene derivatives of thiazolopyrimidines with potential biological activity</strong>

“…Although compounds 4, 5, and 6a had been reported before [8] , the current study provides a more complete characterization. Herein, we have used 1D-and 2D-NMR, as well as mass spectrometry (MS), for the full characterization of all compounds mentioned above (cf.…”

“…We used a multiple component Biginelli-type reaction between benzaldehyde (1), ethyl benzoylacetate (2) and thiourea (3) to obtain the parent compound, ethyl 4,6-diphenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (4), essentially as described [8] (Scheme 1). The thiazolo[3,2-a]pyrimidine 5 was then easily obtained by condensation with either ethyl chloroacetate or chloroacetyl chloride [8] .…”

“…The thiazolo[3,2-a]pyrimidine 5 was then easily obtained by condensation with either ethyl chloroacetate or chloroacetyl chloride [8] . Although 2-arylidene derivatives of 5 could be synthesized in a one-pot process, directly from 4 (Method A) [9] , we obtained better yields and purity using the isolated compound 5 as the starting material for condensation of the corresponding enolate with the appropriate aldehyde in the presence of piperidine (Method B) [8] (Scheme 1). The known compound 6a and its new analogues, 6b and 6c, were thus prepared as racemates in good yields.…”

“…Compound 4 was synthesized as previously described. [8] Briefly, a mixture of benzaldehyde (1 mmol), ethyl benzoylacetate (1 mmol), thiourea (1 mmol) and quartz (0.5 g) in ethanol (15 mL) was refluxed for 3h. After completion of the reaction, as monitored by thin layer chromatography (tlc), the catalyst was filtered off and the solution was kept overnight.…”

“…The precipitate formed on setting was filtered under suction and then recrystallized from ethanol to afford the pure product 4. Compound 5 was synthesized from 4, essentially as described [8] . Comparable results were obtained by reacting 4 (10 mmol) with either a) ethyl chloroacetate (20 mmol) and sodium acetate trihydrate (15 mmol) under reflux in ethanol (30 mL) for 7hr or b) with chloroacetyl chloride (10 mmol) in dry dioxane at room temperature.…”