Peculiar reaction behaviour of barbituric acid derivatives towards aromatic amines

New spiro (thio) barbiturates based on cyclohexanone and bicyclo [3.1.1]heptan-6-one by nonconcerted [1+5] cycloaddition reaction and their conformational structures

“…Representatively, the mechanism for the formation of 7fa'b'' and/or 7fb'b'' is shown in Scheme 2. The nucleophilic attack of 1,3-dimethyl barbituric acid 4b'' to β-position of 3fa' and/or 3fb' as an α,β-unsaturated carbonyl compound (intermolecular Michael addition) [55,56] Representatively, the 1 H NMR spectrum of 7fa'b'' shows two singlets for N-CH 3 protons at δ 2.88 and 3.03 ppm, two doublet of doublets at δ 2.65 and 4.05 ppm for two diastereotopic methylene protons, a triplet at δ 3.75 ppm (essentially, it is doublet of doublets) for benzylic proton on chiral stereogenic center and a multiplet at δ 7.07-7.28 ppm for aromatic phenyl protons. 13 C NMR spectrum of this compound shows thirteen distinct peaks.…”

Behavior of 2‐iminothiazolidin‐4‐one with different reagents

“…In light of the pharmaceutical importance of several fused bicyclic ring systems, the most important are those containing a nitrogen ringjunction, where a nitrogen is common to two rings [11,12], such as levamisole (imidazo [2,1-b]thiazole) (4) [12]. So, the objective of this work was directed to annulate 2-imino-4-thiazolidinone (5) via cycloaddition followed by cyclo-condensation reaction, as a part of our continuing interest in the synthesis of biologically active molecules [13][14][15][16][17].…”

Synthesis, antimicrobial activity and molecular modeling study of substituted 5-aryl-pyrimido[5,4-c]quinoline-2,4-diones

“…Thus, 1 H NMR spectrum of 5c does not show the signals corresponding to AA'-BB' system for a p-substituted benzene ring, however, it showed a new ABX system attributed for 1,2,4-trisubstituted benzene. Previously, we reported a suggested mechanism for the formation of 5a 32 . In general, the suggested mechanism for the formation of pyrimido [5,4-c]quinolines 5a-k, involves addition reaction of aniline derivative 4a-d to the 5-arylidine derivative 3a-d, followed by cyclization to dihydropyrimido [5,4-c]quinoline intermediate which was subsequently autooxidized (Figure 2).…”