Simple and efficient access to pyrazine-2,5- and -2,6-dicarbaldehydes

Abstract

Supporting Information Experimental proceduresCopies of NMR, IR and Raman spectra X-Ray structure data EXPERIMENTAL Measurements. NMR spectra were recorded on Varian SYSTEM 300 and Bruker Avance-III 600 instruments and referenced to residual solvent signal. IR spectra were recorded on Nicolet Avatar 370 FT-IR and Thermo Nicolet 7600 FTIR spectrometer equipped with a Spectra Tech InspectIR Plus microscopic accessory using KBr-diluted samples and diffuse reflectance technique (DRIFT) (128 or more scans at resolution 4 cm -1 ). Raman spectra of solid samples were recorded on a DXR Raman microscope (Thermo Scientific) using excitations at 532 and 780 nm and the laser power at sample from 2 to 5 mW. Mass spectra were recorded with Q-Tof micro (Waters) instrument. Crystallographic data for aldehydes 1, 2 and dihydropyrazine 11 were collected on Nonius Kappa CCD diffractometer equipped with Bruker APEX-II CCD detector, using monochromatic MoKα radiation (λ = 0.71073 Å). The structures were solved by direct methods (SHELXS) [1] and refined by full matrix least squares based on F 2 (SHELXL97). [1] The hydrogen atoms on carbon were fixed into idealized positions (riding model) and assigned temperature factors either H iso (H) = 1.2 U eq (pivot atom) or H iso (H) = 1.5 U eq for methyl moiety. Melting points were measured on Büchi Melting Point B-545 (± 0.2 °C).Materials. Solvents were dried by standard procedures. Silica gel (Merck, 0.040-0.063 mm) was used for column chromatography. A radial-layer chromatograph (Chromatotron) was used for purification of crude products as well. All starting compounds, reagents and solvents were purchased from commercial suppliers. Anhydrous zinc chloride was dried using thionyl chloride. [2] Dimethyl pyrazine-2,5-dicarboxylate, [3] 2,5-bis(chloromethyl)pyrazine [4] and N,N,N´,N´-tetramethyl(benzene-1,2-diamine)-N-oxide [5] were prepared according to the published protocols. Dimethyl pyrazine-2,6-dicarboxylate was prepared by adopting the literature protocol for 2,5-isomer. Both dimethyl pyrazinedicarboxylates were purified by recrystallization/vacuum sublimation (white solids) for further use.

Heterometallic Coordination Polymers with Pyrazine 2,6‐Dicarboxamide: Sequential Metallation of Co(III) and Ag(I)

“…The synthesis was started with commercially available 2, 6‐dimethylpyrazine. It was first oxidized with SeO 2 followed by esterification to afford substituted pyrazine diester 1 . 1 was treated with different amines such as 4‐picolyl amine, 3‐picolyl amine and 2‐picolyl amine resulted three different substituted amides, as 2 a , 2 b and 2 c respectively (Figure ).…”

Self‐Assembly of Cyclohelicate [M3L3] Triangles Over [M4L4] Squares, Despite Near‐Linear Bis‐terdentate L and Octahedral M

“…iii) a: O 3 , MeOH, −78 °C, b: Na 2 S 2 O 5 , continuous extraction (38 %) . iv) OsO 4 , NaIO 4 , THF/H 2 O (2:1), Ar (40±5 %) . v) m ‐CPBA, EtOAc (90 %) .…”