Chemistry of heterocyclic compounds. 98. Syntheses, conformational studies, and reactions of heteromacrocycles. Bis(2-pyridyl) ketone derivatives

Abstract

with chloroform and the combined organic layers were washed with water, saturated brine, and dried (MgS04). The solvent was removed under reduced pressure. The residue and DBU (2 equiv) were refluxed together in benzene under nitrogen for 3 h. The mixture became black and formed a thick precipitate. The reaction mixture was cooled to 20 °C and poured onto excess dilute HC1 and the layers separated. The aqueous layer was extracted with ether and the combined organic layers were washed with water and saturated brine and dried (MgS04). Solvent was removed under reduced pressure, and the residual oils were purified by preparative TLC to give, as the major or only product, the para-substituted product, as shown by NMR comparison with known compounds. Compound 9a gave 12a in 68% yield. Compounds 13a and 13b both gave 14a in 58% yield. Compound 9c gave 12c in 53% yield.General Procedure for Aromatiration of Trisubstituted Diene Diels-Alder Adducts. The dienone 15 (1 equiv) and DBU(1 equiv) were refluxed together in benzene under nitrogen for 3 h. The reaction became black and formed a thick precipitate. The mixture was cooled to 20 °C and poured onto excess dilute HC1. The layers were separated and the aqueous layer was extracted with ether. The combined organic layers were washed with water and saturated brine and dried (MgS04). The solvent was removed under reduced pressure, and the residual oil was purified by preparative TLC to give as the major, or only aromatic product, the para-substituted aromatic as shown by NMR comparison with known compounds. Compounds 15a and 15b both gave 12a in 100% yields. Compounds 15 g and 15 h gave 14 in 70% and 100% yields, respectively. Compounds 15c and 15d gave 12c in 40% and 100% yields, respectively. Compound 15e gave 12e in 88% yield. Compound 15f gave 12f in undetermined yield (due to the presence of MVK dimer).p-(Phenylseleno)acetophenone (12c). Acetyl chloride (0.13 mL, 1.8 mmol) was added dropwise to a stirring solution of diphenyl selenide (0.41 g, 1.8 mmol) and anhydrous aluminum chloride (0.29 g, 2.2 mmol) in carbon disulfide (5 mL) at 20 °C under nitrogen. There was a violent exothermic reaction, and the mixture was stirred for 1.5 h after the addition was completed. The reaction was quenched by pouring onto water (10 mL) and the layers were separated. The aqueous layer was extracted with ether (2 X 10 mL). The combined organic layers were washed with water (10 mL) and saturated brine (10 mL) and dried (MgS04). The solvent was removed under reduced pressure to yield a yellow oil which was purified by preparative TLC eluting with 10% ethyl acetate/hexane to give 13c (0.14 g, 28%). Recrystallization from 95% EtOH gave yellow crystals: mp 47.5-49 °C.

Structural and Magnetic Studies of Copper(II) and Zinc(II) Coordination Complexes Containing Nitroxide Radicals as Chelating Ligands

“…[32,33] A mixture of bis(2-pyridyl) ketone (9.71 g, 51.7 mmol), freshly distilled 2-amino-2-methylpropan-1-ol (110 mL, 1130 mmol), and concentrated H 2 SO 4 (25 drops) in toluene (200 mL) was refluxed for 4 d. The water generated was removed by means of a Dean-Stark trap containing 4-Å molecular sieves. The reaction mixture was then cooled to room temperature and concentrated under reduced pressure.…”

New Synthetic Approach to Polyaryl Strands Containing Pyridine and Pyrimidine Units

“…Ϫ Compounds 1, 7, 8 were obtained according to literature methods. [15,18,19] Ϫ 1 H and 13 C nuclear magnetic resonance spectra were recorded on Bruker AC-300 (300.13 MHz) and Bruker AC-400 (400.13 MHz) spectrometers, chemical shifts are reported in ppm downfield from Me 4 Si. Ϫ IR spectra were obtained on a PerkinϪElmer 983 G spectrometer (as KBr or CsI pellets).…”

A Family of Immobilizable Chiral Bis(pinenebipyridine) Ligands

“…Scheme 1 Synthetic strategy used in the preparation of L3-5 An alternative pathway for the preparation of the key intermediate 6 is by protecting the sterically hindered diaryl keto group of 3 either with 2-chloroethanol in the presence of a weak base, or with ethylene glycol in acidic media. 26 Subsequently the sterically less hindered dioxolane rings protecting the acetyl groups of 4 were selectively hydrolyzed using mild acidic conditions, yielding the desired intermediate 6. Kröhnke annulation using this substrate was found to give bisbipyridine ligand L3 in good yields with no detectable side products.…”

“…26 Subsequently the sterically less hindered dioxolane rings protecting the acetyl groups of 4 were selectively hydrolyzed using mild acidic conditions, yielding the desired intermediate 6. Kröhnke annulation using this substrate was found to give bisbipyridine ligand L3 in good yields with no detectable side products.…”

“…Such enantiopure ligands that can be immobilized on nano supports open new perspectives for 'greener' enantiocatalytic processes in which very specific catalysts can be recovered and reused. 27 Compounds 3, 5, 23 and 7 26 were prepared using literature procedures. Crystals suitable for single-crystal X-ray diffraction were obtained by cooling sat.…”