The First Intramolecular Charge Transfer Transition Based on 2-Ureido-4[1H]-pyrimidinone Binding Module

The first intramolecular charge transfer transition based on 2-ureido-4[1H]-pyrimidinone binding module was reported.     

The mechanism of ureido-pyrimidinone:2,7-diamido-naphthyridine complexation and the presence of kinetically controlled pathways in multicomponent hydrogen-bonded systems

The kinetics of association of ureido-pyrimidinone (U) dimers, present either in the 4[1H]-keto form or in the pyrimidin-4-ol form, with 2,7-diamido-1,8-naphthyridine (N) into a complementary heterodimer have been investigated. The formation of heterodimers with 2,7-diamido-1,8-naphthyridine from pyrimidin-4-ol dimers is much faster than from 4[1H]-pyrimidinone dimers. Using a combination of simple measurements and simulations, evidence for a bimolecular tautomerization step is presented. Finally, the acquired kinetic knowledge of the different pathways leading from ureido-pyrimidinone homodimers to ureido-pyrimidinone:diamido-naphthyridine (U:N) heterodimers allows the prediction and observation of kinetically determined ureido-pyrimidinone heterodimers which slowly convert back to the corresponding homodimers.     

Synthesis of 6-acetylhomopterin. A naturally occurring pyrimido[4,5-b][1,4]diazepine

2-amino-4-oxo-6-acetyl-3,4,7,8-tetrahydro-3H,9H-pyrimido- [4,5-b][1,4]diazepine (or 6-acetylhomopterin), has been synthesised from 1-amino-4,4-diethoxy-3-pentanol and 2-amino-4-chloro-5-nitro-6(1H)-pyrimidinone.     

Photoinduced triplet-triplet energy transfer via the 2-ureido-4[1H]-pyrimidinone self-complementary quadruple hydrogen-bonded module

Phosphorescence quenching and flash photolysis experiments demonstrate that photoinduced intra-assembly triplet-triplet energy transfer can take place via a 2-ureido-4[1H]-pyrimidinone-bridged benzophenone-naphthalene assembly I with a rate constant of 3.0 x 106 s-1 and an efficiency of 95% in CH2Cl2. This new finding suggests that with high binding strength and directionality, the 2-ureido-4[1H]-pyrimidinone hydrogen-bonded module may serve as a new model to illustrate the fundamental principles governing the triplet-triplet energy-transfer process through hydrogen bonds.     

Acetals of lactams and acid amides. 40. Synthesis and hydrolytic cleavage of one-ring and two-ring derivatives of 4-pyrimidinone

The reaction of 1-benzyl-5-cyano-6-dimethylaminomethylene-1, 6-dihydro-4-pyrimidinone with acid leads to 5-benzyl-1,2,7,8-tetrahydropyrido[4,3-d]pyrimidine-1,8-dione, whereas the reaction with ammonia leads to a mixture of 3-cyano-4-benzylamino-2-pyridone and 1-amino-5-benzyl-7,8-dihydropyrido[4,3-d]-pyrimidin-8-one. Heating of the latter in aqueous ethylene glycol is accompanied by recyclization to give 4-benzylamino-5,6-dihydropyrido[2,3-d]pyrimidin-5-one. The reaction of 1-benzyl-4-ditnethylaminomethylene-5-cyano-1,6-dihydro-6-pyrimidinone with ammonia leads to 1-amino-7-benzyl-7,8-dihydropyrido[4,3-d]-pyrimidin-8-one. The rate constants for cleavage of the pyrimidine ring in a number of 4-pyrimidinone derivatives were measured.See [1] for communication 39.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 532–537, April, 1984.     

First fluorescent sensor for fluoride based on 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded AADD supramolecular assembly

A simple, highly selective, neutral, fluorescent sensor for fluoride anions is reported. It is based on 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded AADD supramolecular assembly, and its assembling and disassembling processes are also able to respond to external stimuli reversibly.     

Cyclic tetramer of a metalloporphyrin based on a quadruple hydrogen bond

[reaction: see text] This paper describes the selective formation of a cyclic tetramer from a readily synthesized metalloporphyrin with two self-complementary quadruple hydrogen-bonding units. The extremely strong quadruple hydrogen-bonding unit, 2-ureido-4[1H]-pyrimidinone, enabled the formation of a stable cyclic tetramer based on a tetraphenylporphyrin derivative over a wide concentration range. This hydrogen-bonded tetramer is a new functional unit for use in a higher-ordered architecture of a supramolecular porphyrin assembly.     

Enantioselective cyclization of racemic supramolecular polymers

Homochiral hydrogen-bonded cyclic assemblies are formed in dilute solutions of racemic supramolecular polymers based on the quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidinone unit, as observed by 1H NMR and SEC experiments. Preorganization of the monomers and the combined binding strength of the eight hydrogen bonds result in a very high stability of the cyclic aggregates with pronounced selectivity between homochiral and heterochiral cyclic species, usually only observed in crystalline or liquid crystalline phases.     

Hydrogen-bonded cyclic tetramers based on ureidopyrimidinones attached to a 3,6-carbazolyl spacer

Direct attachment of two 2-ureido-4-[1H]-pyrimidinone (UPy) subunits to a 3,6-carbazolyl core gives rise to a highly viscous, supramolecular polymer. However, insertion of a methylene spacer between the UPy's and the carbazole leads to a well-defined, cyclic tetramer, in a belt-shaped arrangement, as evidenced by MALDI-TOF, DOSY, and NOESY spectra.     

Disulfide exchange in hydrogen-bonded cyclic assemblies: stereochemical self-selection by double dynamic chemistry

Stereoselective cyclization of cystine-based bifunctional 2-ureido-4[1H]-pyrimidinone derivatives in CDCl(3) solutions was demonstrated by (1)H NMR spectroscopy. Thiolate-catalyzed disulfide exchange in solution led to the equilibration of different diastereomers of 1. At low concentrations, where formation of cyclic assemblies is the dominant mode of association, the molecules act as their own template. At these concentrations the meso diastereomer is formed preferentially, indicating a higher stability of its cyclic assemblies under the applied conditions, in comparison to the other diastereomers.     

Singlet-energy transfer in quadruple hydrogen-bonded oligo(p-phenylenevinylene)perylene-diimide dyads

The photophysical properties of a supramolecular donor-acceptor dyad consisting of an oligo(p-phenylenevinylene) unit and a perylene-diimide unit are described. The dyad is created by functionalising the two chromophores with quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidinone units, which provide a high association constant (K approximately 10(8) M-1 in toluene). This feature enabled us to study the time-resolved photoinduced singlet-energy transfer reaction between the two chromophores in dilute solution with transient pump-probe spectroscopy. This energy transfer occurs with a time constant of 5.1 ps.     

Solid-state NMR study of ureidopyrimidinone model compounds

High-resolution (1)H and (15)N{(1)H} solid-state NMR experiments were conducted on two ureidopyrimidinone model compounds: dimeric 2-butylureido-6-methyl-4-pyrimidinone (1) and its bifunctional analogue N,N-1,6-hexanediyl(2-ureido-6-methyl-4-pyrimidinone) (4). High magic angle spinning rates and (1)H decoupling schemes were used to increase the proton spectral resolution. Upon heating 1 to 440 K, an increase in mobility was observed for non-hydrogen-bonded protons; the dimer remained in keto tautomeric form, which is capable of much stronger intermolecular hydrogen bonding than the enol tautomer. From these findings, it was concluded that this ureidopyrimidinone moiety should allow the design of strongly bonded molecular assemblies whose thermal stability compares favourably with that of conventional engineering polymers.     

2-脲基-4[1氢]-嘧啶酮四氢键萘-蒽超分子组装体系:"通过键"机制的单重态能量传递

设计合成了基于2-脉基-4[1氢]-嘧啶酮AADD四氢键萘-葱超分子组装体系UPNa·UPAn.稳态和时间分辨荧光光谱研究表明UPNa·UPAn四氢键组装体可以发生从茶到葱的高效、快速的单重态能量传递过程.体系内光诱导单重态能量传递的速度和效率远大于通过F(o)rster机制的单重态能量传递速率,表明组装体系UPNa·...     

Selective synthesis of fused cyclooctatetraenes by [4 + 4] coupling between two different diene units

In the presence of CuCl and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, the [4 + 4] coupling between zirconacyclopentadienes and 1,3-diiodobutadienes fused through an oxygen or nitrogen five-membered ring proceeded at ambient temperature to afford fully substituted polycyclic cyclo-octatetraenes in good yields. The fused ring moiety of the diiodides plays a critical role. The corresponding acyclic diiodide and a cyclohexane-fused analogue gave no coupling product, and a cyclopentane derivative showed only moderate reactivity. Correlation of the structures of the diiodides and their reactivity was established by an X-ray and density functional study.     

Conformational control in the cyclization of hydrogen-bonded supramolecular polymers

Bifunctional 2-ureido-4[1H]-pyrimidinone (UPy) derivatives can form small cyclic oligomers as well as long supramolecular polymers in chloroform solutions using the quadruple hydrogen-bonding motif. Ring-chain equilibria of a set of supramolecular monomers containing methyl-substituted alkyl linkers between the hydrogen-bonding UPy moieties were investigated by (1)H NMR spectroscopy and viscometry. The data were characterized in terms of critical concentration (CC, denoting the onset of polymerization) and equilibrium cyclic dimer concentration (EDC, representing preorganization of the monomer toward selective formation of cyclic dimer). Methyl substituents in the monomer were found to promote conformations favorable for cyclic dimerization, leading to an increase in both the EDC and the CC with respect to unsubstituted monomer. Furthermore, we observed an odd-even effect in the CC and EDC with increasing length of the linker between the hydrogen-bonding units. The combined results allow tuning of the critical concentration over a broad range and offer detailed information on the correlation between monomer structure, conformation, and polymerizability which may provide new insights for the study and design of other ring-chain equilibria or helix-random coil transitions.     

Generation-independent dimerization behavior of quadruple hydrogen-bond-containing oligoether dendrons

[reaction: see text] A new series of self-assembling G1-G3 dendronized dimers bearing oligoether dendrons and a dimeric 2-ureido-4-pyrimidinone (UPy) quadruple hydrogen-bonding core were prepared and characterized. It was found that the nonpolar microenvironment created by the dendrons preserved the UPy unit in its DDAA tautomeric form. As a result, the stabilities of the dimers were exceptionally strong for all three generations (K(dim) > 2 x 10(7) M(-)(1) in CDCl(3) at 25 degrees C). Furthermore, the steric size of the dendrons did not exhibit a significant effect on their dimerization behavior.     

Pyrimidines. 24. Analogues and derivatives of 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP)

Preparation of a number of derivatives of 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP) including the 2-dialkylaminoalkylamino-, 2-hydroxyalkylamino-, 2-ethoxycarbonylamino- and 2-alkylaminocarbonyl-amino- groups substituted on the pyrimidine ring as well as preparation of 1-(alkylaminoalkyl)-4,6-dioxo-8-phenyl-2,3,4,6-tetrahydro-1H-pyrimido[1,2-α]pyrimidines and 3,5-dioxo-7-phenyl-1,2,3,5-tetrahydroimidazo-[1,2-α]pyrimidines with or without the bromo-substitution are reported.     

1,3,4-Oxadiazolo[3,2-α]pyrimidinium salts

5-Amino-1,3,4-oxadiazolium perchlorates react with 1,3-carbonyl-functional compounds to give 1,3,4-oxadiazolo[3,2-α]pyrimidinium perchlorates. The latter are cleaved by both alkali and strong acid to give 1-amino-2-pyrimidinone or 5-amino-1,3,4-oxadiazole derivatives. The l,3,4-oxadiazolo[3,2-α]pyrimidinium perchlorates react with anailine and hydrazines to give sym-triazolo[1,5-α]pyrimidinium salts and with acetylacetone to give pyrazolo[1,5-α]pyrimidines.     

Synthesis and study of 2-(1-pyrazolyl)purine derivatives

Derivatives of 2-(1-pyrazolyl)-4(3H)-pyrimidinone and 2-(1-pyrazolyl)purine were obtained, and their UV and IR spectra were studied. It is shown that alkyl derivatives of hypoxanthine and 6-chloro- and 6-ethoxypurine exist in the 7H form, which is stabilized by an intramolecular hydrogen bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1404–1406, October, 1977.     

Parallel solution-phase synthesis of 4-dialkylamino-2-methylsulfonyl-6-vinylpyrimidines

A simple and straightforward methodology for the parallel, solution-phase synthesis of novel 4-dialkylamino-2-methylsulfonyl-6-vinylpyrimidines 9a-j has been developed. Starting from 2-methylthio-6-[2-(p-toluensulfonyloxy)ethan-1-yl]-4(3H)-pyrimidinone (6), a three-step procedure (namely, tosylate substitution by amines, base-catalyzed rearrangement, and sulfide to sulfone oxidation) using a Buchi Sincore synthesizer gave the final products in high yield after simple ethyl acetate extraction and without further purification. Interestingly, when the final oxidation step was performed on 4-arylpiperazine derivatives 8g-j, the corresponding highly polar piperazine N-oxides 9g-j were obtained, which conversely needed chromatographic purification in order to give the pure products.