Molecular length distribution and the formation of smectic phases

• Nadia Kapernaum,
• C. Scott Hartley,
• Jeffrey C. Roberts,
• Robert P. Lemieux and
• Frank Giesselmann

Beilstein J. Org. Chem. 2009, 5, No. 65, doi:10.3762/bjoc.5.65

• -(tetradecyloxy)pyrimidine) [1], where the aromatic core is substituted symmetrically with two alkoxy chains each with 14 methylene units. It exhibits a molecular length of 45.5 Å. For the short compound we used either the phenylpyrimidine 2PhP (2-[4-(butyloxy)phenyl]-5-(octyloxy)pyrimidine) [1] or the

• occur. Therefore, the structure of bidisperse smectics is signified by extensive out-of-layer fluctuations. Experimental Compounds 2-[4-(tetradecyloxy)phenyl]-5-(tetradecyloxy)pyrimidine (PhP14) [1], 6-[4-(butyloxy)phenyl]-3-(octyloxy)pyridazine (6PhPz) [3] and (R,R)-2-[4-(octyloxy)phenyl]-5-(2,3

• -difluorohexyloxy)pyridine (MDW510) [7] were synthesized according to published procedures and shown to have the expected physical and spectral properties. The liquid crystal 2-[4-(butoxy)phenyl]-5-(octyloxy)pyrimidine (2PhP) was obtained from a commercial source. X-Ray scattering experiments were performed with Ni

Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

• Gundula F. Starkulla,
• Elisabeth Kapatsina,
• Angelika Baro,
• Frank Giesselmann,
• Stefan Tussetschläger,
• Martin Kaller and
• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 63, doi:10.3762/bjoc.5.63

• hydrogen bonds seems to completely suppress the formation of mesophases. Furthermore, the polar pyrimidine ring seems to play an important role in promoting liquid crystalline properties. Experimental General Melting points were measured on a Mettler Toledo DSC822 and are uncorrected. NMR spectra were

Synthesis of 2-substituted 9-oxa-guanines {5-aminooxazolo[5,4-d]pyrimidin- 7(6H)-ones} and 9-oxa-2-thio- xanthines {5-mercaptooxazolo[5,4-d]pyrimidin- 7(6H)-ones}

• Subrata Mandal,
• Wen Tai Li,
• Yan Bai,
• Jon D. Robertus and
• Sean M. Kerwin

Beilstein J. Org. Chem. 2008, 4, No. 26, doi:10.3762/bjoc.4.26

• can be considered as 9-oxa-purine analogs of naturally occurring nucleic acid bases. Interest in this ring system has increased due to recent reports of biologically active derivatives. In particular, 5-aminooxazolo[5,4-d]pyrimidine-7(6H)-ones (9-oxa-guanines) have been shown to inhibit ricin. The

• to naturally occurring nucleic acid bases, this heterocyclic ring system continues to generate interest. Approaches to the oxazolo[5,4-d]pyrimidine ring system generally involve either cyclodehydration of an 5-(acylamino)-4-hydroxypyrimidine [6][7][8][9][10] or elaboration of a 4-cyano- or 4

• unsuccessful. An alternative route was sought in which the oxazole ring was formed first, followed by elaboration of the pyrimidine ring. Our previous work had demonstrated that in the case of ethyl 5-amino-2-methyloxazole-4-carboxylate 3a [20], direct annulation with chloroformamidine in DMSO at 120 °C or

Perhalogenated pyrimidine scaffolds. Reactions of 5-chloro- 2,4,6-trifluoropyrimidine with nitrogen centred nucleophiles

• Emma L. Parks,
• Graham Sandford,
• John A. Christopher and
• David D. Miller

Beilstein J. Org. Chem. 2008, 4, No. 22, doi:10.3762/bjoc.4.22

• functionalised pyrimidine derivatives are of great importance to the life-science industries and there exists a need for efficient synthetic methodology that allows the synthesis of polysubstituted pyrimidine derivatives that are regioselective in all stages to meet the demands of RAS techniques for applications

• in parallel synthesis. 5-Chloro-2,4,6-trifluoropyrimidine may be used as a scaffold for the synthesis of polyfunctional pyrimidine systems if sequential nucleophilic aromatic substitution processes are regioselective. Results Use of 5-chloro-2,4,6-trifluoropyrimidine as a core scaffold for the

• synthesis of functionalised pyrimidine systems is assessed in reactions with a small range of nitrogen centred nucleophiles. Mixtures of products arising from nucleophilic aromatic substitution processes are formed, reflecting the activating effect of ring nitrogen and the steric influences of the chlorine

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

• Jun Xu,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2008, 4, No. 18, doi:10.3762/bjoc.4.18

• . Results and Discussion On installation of pyrimidine bases into the gem-difluorinated allylic carbonates 1 and 4, our group found that the γ-substitution products 2, 3 and 5 were surprisingly generated exclusively in good yields, respectively, when the compounds 1 and 4 reacted with suitably protected

An easy synthesis of 5-functionally substituted ethyl 4-amino- 1-aryl- pyrazolo- 3-carboxylates: interesting precursors to sildenafil analogues

• Said A. S. Ghozlan,
• Khadija O. Badahdah and
• Ismail A. Abdelhamid

Beilstein J. Org. Chem. 2007, 3, No. 15, doi:10.1186/1860-5397-3-15

• -arylhydrazononitriles 1a-c react readily with chloroacetonitrile, ethyl chloroacetate, and with phenacyl chloride to give 4-aminopyrazoles 4a-e. The pyrazolo[4,3-d]pyrimidine derivatives 7 and 10 are synthesized via reaction of the aminopyrazole 4b with phenylisothiocyanate and DMFDMA/NH4OAc respectively. Background

• Interest in the chemistry of 4-aminopyrazole carboxylic acid derivatives has recently been recognized as their derivatives are ideal precursors for the synthesis of biologically active pyrazolo[4,3-d]pyrimidine ring systems [1][2][3][4][5][6]. The reported synthetic approaches to these derivatives are also

• expected. Compound 9 could be readily converted into pyrazolo[4,3-d]pyrimidine 10 on treatment with AcOH/NH4OAc mixture. (cf. Scheme 3) Compound 1 reacted with hydroxylamine hydrochloride in ethanol/sodium acetate solution to yield amidooxime 11 as in the literature [10]. Trials to cyclize the amidooxime

2-Arylhydrazononitriles as building blocks in heterocyclic synthesis: A novel route to 2-substituted- 1,2,3-triazoles and 1,2,3-triazolo[4,5-b]pyridines

• Saleh M. Al-Mousawi and
• Moustafa Sh. Moustafa

Beilstein J. Org. Chem. 2007, 3, No. 12, doi:10.1186/1860-5397-3-12

• [4,5-b]pyridine 8. Treatment of acetyl derivative 6 with DMFDMA gave enaminone 9. The enaminone 9 was coupled with benzenediazonium chloride to yield phenylazo-1,2,3-triazolo [4,5-b]pyridine 10. Trials to convert compound 14 into 1,2,3-triazolo [4,5-d]pyrimidine 15 via refluxing in AcOH/NH4OAc failed

Microwave assisted synthesis of triazoloquinazolinones and benzimidazoquinazolinones

• Aboul-Fetouh E. Mourad,
• Ashraf A. Aly,
• Hassan H. Farag and
• Eman A. Beshr

Beilstein J. Org. Chem. 2007, 3, No. 11, doi:10.1186/1860-5397-3-11

• or a completely reduced pyrimidine nucleus are of interest, since they display valuable pharmaceutical activities. [1][2] There has been an increasing interest in the chemistry of 4(3H)-quinazolinones because of their biological significance. Many of them show antifungal, [3] antibacterial, [4

Tether- directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

• Peter J. Jervis and
• Liam R. Cox

Beilstein J. Org. Chem. 2007, 3, No. 6, doi:10.1186/1860-5397-3-6

• precursors in hand, we were ready to conduct our intramolecular allylation study. Each aldehyde substrate (>95:5 d.r. in all four cases) was treated with TMSOTf in the presence of 2,4,6-tri-t-butyl pyrimidine (TTBP), [24] which acts as a Brønsted acid scavenger, in CH2Cl2 as solvent, conditions that had

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• synthesis of 5-hydroxyorotic acid from orotic acid is markedly affected by oxygen [5] but in a way opposite to the more usual observation that yields are improved by excluding oxygen. Here, in the absence of oxygen, yields are low and the pyrimidine ring undergoes cleavage to urea. Oxygen inhibits this side

Microwave- assisted ring closure reactions: Synthesis of 8-substituted xanthine derivatives and related pyrimido- and diazepinopurinediones

• Joachim C. Burbiel,
• Jörg Hockemeyer and
• Christa E. Müller

Beilstein J. Org. Chem. 2006, 2, No. 20, doi:10.1186/1860-5397-2-20

• -noradamantyl)carboxamido-6,8-dioxo-7-propyl-1,3,4,6,7,8-hexahydro-2H-pyrimido [1,6-a]pyrimidine (13) to the corresponding tricyclic derivative 5 was previously performed by heating it with HMDS under reflux conditions for 18 h [6]. We expected that microwave irradiation might shorten the reaction time here

• pyrimidopurine derivative 5 the addition of ammonium sulfate did not affect the reaction at all. Subsequently, we further investigated the scope of the method. We had previously demonstrated that pyrimido [1,6-a]pyrimidine derivatives like 13 and 15 could be converted to the tricyclic pyrimido [1,2,3-cd]purine

• -noradamantyl)carboxamido-6,8-dioxo-7-propyl-1,3,4,6,7,8-hexahydro-2H-pyrimido [1,6-a]pyrimidine (13) [6] (1.0 g, 8.4 mmol) in THF (3 ml) in a 10 ml pressure vial, HMDS (2 ml) was added. Microwave irradiation was applied (100 W, 140°C) for 20 min. The resulting yellow solution was hydrolyzed with 6 ml of

An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium- catalyzed multi- component domino reaction

• Dipak Prajapati and
• Mukut Gohain

Beilstein J. Org. Chem. 2006, 2, No. 11, doi:10.1186/1860-5397-2-11

• reaction of α,β-ethylenic ketones and ethyl vinyl ether or 2,3-dihydrofuran has remained unexplored.[11] Herein, we report the first example of indium(III) chloride catalysed synthesis of fused pyrimidine derivatives via a multicomponent domino Knoevenagel hetero Diels-Alder reaction. The reaction proceeds

• efficiently at ambient temperature in excellent yields (Scheme 1). Pyrimidine derivatives continue to be of great interest due to their wide range of biological activities.[12] Preparation of naturally occuring complex molecules containing a uracil ring pose significant synthetic challenges.[13] The

• , [19][20][21] most of which rely on multi-step reactions with yields being low. [22][23] The furo [2,3-d]pyrimidine derivatives act as useful sedatives, antihistamines, diuretics, muscle relaxants and antiulcer agents. Furthermore, pyrano [2,3-d]pyrimidines also represent broad classes of annelated

Crystal engineering of analogous and homologous organic compounds: hydrogen bonding patterns in trimethoprim hydrogen phthalate and trimethoprim hydrogen adipate

• Packianathan Thomas Muthiah,
• Savarimuthu Francis,
• Urszula Rychlewska and
• Beata Warżajtis

Beilstein J. Org. Chem. 2006, 2, No. 8, doi:10.1186/1860-5397-2-8

• Trimethoprim [2,4-diamino-5-(3',4',5'-trimethoxybenzyl)pyrimidine] is an antifolate drug. It selectively inhibits the bacterial dihydrofolate reductase (DHFR) enzyme. Results In the crystal structures of trimethoprim (TMP)-hydrogen phthalate (1) and trimethoprim-hydrogen adipate (2), one of the N atoms of the

• pyrimidine ring is protonated and it interacts with the deprotonated carboxylate oxygens through a pair of nearly parallel N-H...O hydrogen bonds to form a fork-like interaction. In the compound 1, the pyrimidine moieties of the TMP cations are centrosymmetrically paired through a pair of N-H...N hydrogen

• bonds involving 4-amino group and the N (N3) atom of the pyrimidine rings to form a 8-membered hydrogen bonded ring [R22(8)]. The 4-amino group of one TMP moiety and 2-amino group of another TMP moiety (both moieties are members of a base pair) are bridged by the carbonyl oxygen of the phthalate moiety

One-pot synthesis of novel 1H-pyrimido[4,5-c][1,2]diazepines and pyrazolo[3,4-d]pyrimidines

• Dipak Prajapati,
• Partha P. Baruah,
• Baikuntha J. Gogoi and
• Jagir S. Sandhu

Beilstein J. Org. Chem. 2006, 2, No. 5, doi:10.1186/1860-5397-2-5

• heteroannulation of uracils usually require either forcing conditions[16][17] or relatively longer synthetic pathways.[18] Also, pyrazolo [3,4-d]pyrimidines are a class of naturally occurring fused uracils that possess a wide range of biological activity.[19] Allopurinol (6-dehydroxy-pyrazolo [3,4-d]pyrimidine

• pyrimidine derivative, which will not only increase the synthetic scope of this hitherto under-developed reaction, but it will expand the synthetic versatility of uracil derivatives and provide diversity in the nature of the heterocyclic motif in a targeted library of potential products. Results and

• , we have isolated the corresponding 2,4-dioxo-pyrazolo [3,4-d]pyrimidine 6a in 80% yield instead of the expected seven-membered pyrimido[1,2]diazepine 7 or any other product (Scheme 3). The structure of the product 6a thus obtained was confirmed unambiguously by high resolution spectral techniques. To