Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones and Their Corresponding 2(1H)Thiones Using Trichloroacetic Acid as a Catalyst under Solvent-Free Conditions

Abstract

Trichloroacetic acid was found to be a convenient catalyst for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones and their corresponding 2(1H)-thiones through a one-pot three-component reaction of aldehydes, alkyl acetoacetate, and urea or thiourea at 70°C under solvent-free conditions.

Iron-catalyzed four-member multicomponent reaction for assembly of (E)-6-arylvinyl-3,4-dihydropyrimidin-2(1H)-ones

“…It is noteworthy that as one of the most important applications, very recently, we have used compounds 4 to prepare potential bioactive pyrido [4,3-d]pyrimidines 6 in the presence of NaOH in EtOH at reflux. 5 This chemistry was also extended to the other b-dicarbonyl compounds such as ethyl acetoacetate (1u) and acetylacetone (1v), but they only gave the corresponding Biginelli products 5u and 5v in 85% and 81% yields, respectively (Eq. 4).…”

“…(5) is very important for this vinylogous aldol condensation reaction. 5 A possible mechanism of the tandem Biginelli reaction/vinylogous aldol condensation is proposed in Scheme 1. We proposed a mechanism for the first stage (1 to 5) similar to that of Folkers and Johnson, 6k Kappe, 6j Hu, 6i and Lu 6d for Biginelli reaction.…”

“…For the vinylogous-aldol reaction stage, the vinylogous enolate C 12a,15 was firstly formed in the presence of FeCl 3 . The nitrogen of the amide moiety contributed its lone-pair electrons to the conjugated system, which would enhance the nucleophilicity of the vinylogous enolate C. 5,16 The addition of the reactive species C to aldehydes 2 with the terminal carbon of its double-bond system (the g-carbon/position), followed by dehydration to afford the products 4. 16d,17…”

“…The known compounds 4aae4aj, 4ap, and 4b were identified by comparison of their 1 H NMR with those of authentic samples. 5 The new compounds (4ake4ao) listed in Table 2 were properly characterized by melting point, 1 H NMR, 13 C NMR, and HRMS. 1 H NMR and 13 C NMR spectra were recorded on a 400 MHz NMR spectrometer ( 1 H: 400 MHz, 13 C: 100 MHz at 25 C).…”

“…Please cite this article in press as:Zhang, Z.; et al, Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.07.039 amount of the benzaldehyde to 3 equiv or carried out the reactions in the presence of molecular sieve under anhydrous condition. The Biginelli products bearing 5-ester or 5-acyl group are not the substrates of vinylogous aldol reaction under present conditions.…”