Preparation, structures and preliminary host–guest studies of fluorinated syn-bis-quinoxaline molecular tweezers

• Markus Etzkorn,
• Jacob C. Timmerman,
• Matthew D. Brooker,
• Xin Yu and
• Michael Gerken

Beilstein J. Org. Chem. 2010, 6, No. 39, doi:10.3762/bjoc.6.39

• reported procedures [29][30][31][32] did not significantly alter the outcome. It should be noted that all fluorinated bis-quinoxalines are stable compounds which do not show any decomposition over extended periods of time; loss of fluorine has only been observed under typical nucleophilic aromatic

• substitution conditions. Although the new compounds, in particular the cyclohexadiene-derived species 15b–c, were reasonably soluble in dipolar aprotic solvents (DMSO, DMF) or halogenated aromatic solvents (C6H5Cl), they only displayed poor solubility in several standard organic solvents (CHCl3, CH2Cl2, CH3OH

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

• 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

• derivatives can be isolated in acceptable yields using this methodology. Keywords: pyrimidine; rapid analogue synthesis; perfluoroheteroaromatic; nucleophilic aromatic substitution; Introduction Highly functionalised pyrimidine derivatives are of great importance to the life-science industries and, indeed

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• electron withdrawing behavior to the alkoxy group but also acts to deactivate the aromatic ring system [53]. Electrophilic Aromatic Substitution Trifluoromethoxybenzene, for example, undergoes nitration considerably (up to 5 times) more slowly than benzene. The electrophilic substitution occurs selectively

Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl

• Lukas Hintermann

Beilstein J. Org. Chem. 2007, 3, No. 22, doi:10.1186/1860-5397-3-22

• them from participating as electrophiles in aromatic substitution reactions. Conclusion The useful imidazolium salts IPr·HCl (1), IMes·HCl (2) and IXy·HCl (3) have previously been synthesized by a range of methods giving the products in variable purity and yields. We now present a protocol for the