The conformational flexibility and effects of the substituents in 2-oxo-and 2-thioxo-1,2,3,4-tetrahydropyrimidines were studied by the semiempirical quantum-chemical AMI method. The substituents at the double bond have no appreciable effect on the conformational characteristics of the heterocycle. The introduction of substituents to the saturated carbon atom results in the conversion of the tetrahydrocycle to a half-chair conformation and in a substantial decrease in the ring flexibility. The results of calculations are confirmed by the X-ray study of both compounds.Key words: 2-oxo-l,2,3,4-tetrahydropyrimidine, 2-thioxo-l,2,3,4-tetrahydropyrimidine, conformational analysis, AMI, molecular structure, X-ray study.Studies of the conforrnational flexibility of six-membered carbo-and heterocycles we had undertaken recently I-3 showed that it is a property intrinsic in dihydrogenated rings of all types. The previously studied compounds contained two endocyclic double bonds. At the same time, the tetrahydropyrimidine cycle in the uracyl molecule was also shown to possess a high conforrnational flexibility) In this connection it was of interest to study this property in other tetrahydro analogs of dihydroazines.This work is dedicated to the investigation of the molecular structure al 3 A / R2"7- and conformational flexibility of 2-oxo-and 2-thioxo-1,2,3,4-tetrahydropyrimidines as well as of their 4-phenyl-, 5-carbomethoxy-, and 6-rnethytsubstituted derivatives (1--16). ExperimentalThe structures of molecules 1--16 were calculated by the semiempirical quantum-chemical AIM 1 method 5 with full geometry optimization. The conformational flexibility of tetrahydro cycles was studied by scanning the C(=X)--N--C(sp3)--C= torsion angle in the +30 ~ interval for compounds 1--3, 5, 9--11, 13 and in the +40 ~ to -30 ~ interval for molecules 4, 6--8, lZ, 1,1--16 with an increment of I0 ~ and full optimization of the remaining geometric parameters of the molecules_ The results of calculations are listed in Tables 1 and 2. X-ray study of compounds 20 and 21. Crystals of compound 20 are triclinic. The parameters obtained at 20 ~ are a = 7.347(4), b = 9.503(11), e = 12.273(14) A, ct = 71.80(4) ~ , 13 = 88-38(4) ~ , ~ = 70.31(4)% V-777(1) A 3, dca]c = 1.519 g cm -3, ~t = 2.78 mm -l, space group P~, and Z = 2. The intensities of 2755 independent reflections (Rim -----0.08) were measured on an automatic four-cimle Syntex P21 diffractometer ()~-Mo-Kct, 1t-filter, 0/2_0 scan, 20ma x = 50~ The profile analysis of the totality of reflections obtained was performed using the PROFIT programflThe structure was solved by direct methods using the SHELXTL PLUS 5.0 program package. 7 The absorption correction was introduced semiempirically using the W-scan data ( Tmin = 0.603, Tma x = 0.891 ). The positions of hydrogen atoms were calculated geometrically and refined using the riding model with fixed Uis o values for the C or N atom bonded to the corresponding H atoms (5]so = n(f~q, n = 1.5 for the H atoms

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The reaction of aroyl[bis(4 hydroxycoumarin 3 yl)]methanes with 1,2 phenylenediamines in Pr i OH is accompanied by the recyclization to 8 R or 7 R 4 (2 hydroxyphenyl) 1,5 benzodiazepin 2 ones, whereas the reaction with o phenylenediamine and its 4 methyl sub stituted derivatives in MeOH produces organic ionic salts of the bis coumarin anion with monoprotonated o phenylenediamine as the cation.Key words: aroyl[bis(4 hydroxycoumarin 3 yl)]methanes, 4 R 1,2 diaminobenzenes, 8 R (7 R) 4 (2 hydroxyphenyl) 1,5 benzodiazepin 2 ones, recyclization, ionic salts, X ray diffraction study.Various 4 hydroxycoumarin derivatives have found use as drugs. 1-5 Among these is neodicoumarin (ethyl di(4 hydroxycoumarin 3 yl)acetate), which is used in medicine as an anticoagulant. 6 These bis adducts based on heterocyclic CH acids and active carbonyl compounds (aldehydes or glyoxals) have attracted interest because their molecules contain several electrophilic centers, thus giving promise that various heterocyclization path ways are possible in the reactions with binucleophilic re agents.Earlier, 7 we have demonstrated that the reaction of aryl(aroyl)[bis(5,5 dimethyl 1,3 dioxocyclohexan 2 yl)]methanes with o phenylenediamine (o PDA) produces hexahydrobenzo[b,e] 1,4 diazepin 1 one derivatives 1A or 9 aryl(aroyl) 10 (2 aminophenyl)decahydroacridine 1,8 dione derivatives 2 depending on the electronic char acter of the substituent in the aryl or aroyl fragments. Electron withdrawing substituents in the aromatic moi ety facilitate the formation of the diazepine ring, whereas the formation of acridones is typical of the starting polyketones containing electron releasing substituents in the benzene ring.In the present study, we investigated the reaction of 4 R benzoyl[bis(4 hydroxycoumarin 3 yl)]methanes 3a-c with o PDA (4a) and its substituted derivatives 4b-d with the aim of synthesizing diazepines 1B, which are structurally similar to diazepines 1A and in which the diazepine fragment is annulated with the coumarin ring. The starting ketones 3a-c were synthesized in good yields by heating 4 hydroxycoumarin with p substituted aryl glyoxals in AcOH for a short period of time. Their struc tures were confirmed by 1 H NMR spectra, which show singlets for the methine protons at δ 6.2-6.4 and multi R = Ar, COAr

Abstract:The 1 H-NMR and quantum chemical analysis of the stability of tautomers of cinnamoyl pyrone derivatives and vinylogs has been studied. The relationship between the structure of the most stable tautomer and its spectral properties has been investigated. It has been determined that the tautomer of highest stability (88-100 molar %) has an α-pyrone structure and exhibits a trans-conformation in the cinnamoyl fragment. An intense fluorescence of dyes has been observed in non-polar solvents with cinnamoyl fragments having electron-donating substituents or several double bonds in the polymethine chain. A gradient in solvent polarity resulted in fluorescence quenching which permits the use of the dyes as intensometric fluorometric probes for medium polarity examination. Sp. z o.o. © Versita

The regioselective three-component condensation of azomethine ylides derived from isatins and α-amino acids with acrylamides or aroylacrylic acids as dipolarophiles has been realized through a one-pot 1,3-dipolar cycloaddition protocol. Decarboxylation of 2'-aroyl-2-oxo-1,1',2,2',5',6',7',7a'-octahydrospiro[indole-3,3'-pyrrolizine]-1'-carboxylic acids is accompanied by cyclative rearrangement with formation of dihydropyrrolizinyl indolones.117