Three series of organoboron-based molecules, including biphenyls 1a, 1b, 1c, diphenylacetylenes 2a, 2b, 2c, and stilbenes 3a, 3b, 3c, in which the electron-accepting boryl and the electron-donating amino groups are introduced at different positions, have been comprehensively investigated to explore the effect of the substitution pattern on the intramolecular charge-transfer emissions. In cyclohexane solution, the change of substitution pattern from p,p′ to o,p′ by introduction of boryl at the lateral o-position rather than the terminal p-position leads to bathochromism in the absorption and emission spectra. With further variation of the amino position from the terminal p′-position in o,p′-substitution to the lateral o′-position in an o,o′-substitution pattern, a blueshift was observed in the absorption owing to the less-efficient conjugation extension of the amino group as the result of sp³ hybridization. It is notable that the emission of the three series of molecules changes with completely different trends. Only the emission of the biphenyl is redshifted further from o,p′-substituted 1b to o,o′-substituted 1a, whereas o,o′-substituted diphenylacetylene 2a maintains almost the same spectrum as that of o,p′-substituted diphenylacetylene 2b and the fluorescence of o,o′-substituted stilbene 3a is even blueshifted compared with o,p′-substituted stilbene 3b. As a result, the o,o′-substituted biphenyl 1a shows the longest emission wavelength despite the limited conjugation of the parent biphenyl skeleton. The long emission wavelength of 1a may arise from its extremely twisted structure, which would cause a significant structural relaxation in the exited state. In the solid state, 1a still keeps almost the longest emission wavelength. In addition, its quantum yield is also among the highest. The unusual properties, intense solid-state emission together with long emission wavelength, and particularly large Stokes shift, which are difficult to attain by structural modification of other parent π-conjugated frameworks, have been achieved by the introduction of boryl and amino groups at the o,o′-positions of the biphenyl skeleton.

A novel seven-step methodology for the synthesis of N-substituted-6-alkoxypteridin-4-amine has been developed with the total yields of 35.4–41%. Twenty new compounds were synthesized by heterocyclization of easily prepared 3-amino-6-bromopyrazine-2-carboxamide, subsequent alkoxylation, chlorination, and nucleophilic substitution. Their structures were confirmed by ¹H-NMR, ¹³C-NMR, ESI-MS, and elemental analysis. The structure of N-(3-chloro-4-fluorophenyl)-6-ethoxypteridin-4-amine was further determined by X-ray crystallographic analysis. It was found that different chlorinating reagents gave different products. The possible chlorination mechanism was discussed.

A series of novel 2-aryl-3-ethoxycarbonyl-4-phenylpyrido[1,2-a]benzimidazole derivatives were synthesized by the tandem reaction of 2-benzoyl benzimidazole and (Z)-ethyl 4-bromo-3-arylbut-2-enoate in the presence of potassium carbonate. The compounds were characterized using IR, ¹H-NMR, ¹³C-NMR, HRMS and the structure of 6f was further determined by X-ray crystallography. Both absorption and fluorescence spectra characteristics of the compounds were investigated in acetonitrile and dichloromethane. The results showed that the absorption maxima of the compounds varied from 220 to 284 nm, depending on the structure of 2-aryl group. The fluorescence results revealed that these compounds exhibited blue-green fluorescence (463–475 nm) in dilute solutions and showed acceptable fluorescence quantum yields (Ф_PL = 0.13–0.73) in dichloromethane. Copyright © 2011 John Wiley & Sons, Ltd.

A series of novel pyrazole-based lipoprotein-associated phospholipase A₂ (Lp-PLA₂) inhibitors have been designed and synthetized by a variety of acetophenones via a 10-step convergent approach. The synthetic approach is carefully optimized, and an unsuccessful alternative route is also discussed. The in vitro biological activity reveals that all the synthesized compounds are potent Lp-PLA₂ inhibitors with compound 13b being the most potent one (Lp-PLA₂, IC₅₀=1.5 nmol/L).

The synthesis of a designed, sterically congested geminal dimethyl-bearing PAR-1 antagonist was achieved by a route of ten steps, with the oxidation of an electron-rich benzaldehyde, the construction of a tertiary alkyl azide, and the selective hydrogenolysis of a 1,5-fused tetrazole to generate the cyclic amidine with Raney-Ni being the key steps. The selective hydrogenolysis of 1,5-fused tetrazole to generate the cyclic amidine with Raney-Ni was discovered and may be generally used for the synthesis of structurally unusual cyclic amidines. Several unsuccessful attempts to construct the desired geminal dimethyl-bearing cyclic amidine were also discussed.