Tertiary amine oxides. XVIII. The reduction of 1-[(1-oxido-2-pyridyl)methyl]pyridinium salt was written by Hamana, Masatomo;Umezawa, Bunsuke;Noda, Kanji. And the article was included in Chemical & Pharmaceutical Bulletin in 1963.COA of Formula: C9H8N2O This article mentions the following:
By a modified King reaction, 2-picoline 1-oxide (I), C5H5N, and iodine in the molar ratio 1:2:1 refluxed 5 hrs. in dioxane gave 16% title compound (II) (X = I), m. 180-1° (decomposition). Change of solvent to xylene in the same procedure yielded unexpectedly 5% pyrido[1′,2′:3,4]imidazo[1,g-a]pyridinium salt (III) (X = I), m. 252-3°; picrate m. 217-18°. The structure of III was confirmed by a 2nd synthesis, whereby 2-(BrCH2)C5H4N and 2-BrC5H4N were refluxed 20 hrs. in MeCN to effect cyclization and to yield, after chromatography over Al2O3-Celite (2:1), 18% III (X = Br), m. 150-2°, converted to III (X = I) in 100% yield by refluxing 4 hrs. with NaI in Me2CO. The identity of the 2 samples of III (X = I) was established by both infrared and ultraviolet absorption spectra (curves shown). Refluxing II 5 hrs. in xylene, or with C5H5N.HI in xylene, or with iodine in xylene gave III in, resp., a small amount, 64%, and 53% yields. However, refluxing 1-(2-pyridylmethyl)pyridinium bromide (IV) 5 hrs. with C5H5N.HI in xylene left only unchanged IV; picrate m. 169-70°. This result indicated the essential role of the N-oxide group of H in the formation of III. Chromatography on Amberlite IRA-400 (Cl– or HO– type) effected the anion exchange in II (from X = I to X = Cl or HO). The selective reduction of either the N-oxide or the pyridinium group of II was studied under varied conditions. Catalytic hydrogenation (Raney Ni) of II (X = Cl) in MeOH or 4% AcOH, after absorption of 1 molar equivalent H, yielded, resp., 43 or 41% IV, and after absorption of 4 molar equivalents H, 74 or 91% N-(2-pyridylmethyl)piperidine (V), b4 100-15°; picrate m. 180-2°. Thus, Raney Ni was specific for the N-oxide rather than for the pyridinium reduction Catalytic hydrogenation (Raney Ni) of II (X = HO) after absorption of 4 molar equivalents H yielded (in MeOH solution) 71% V, and (in 1% NaOH solution) 91% V. II (X = Cl) catalytically reduced with Pd-C in acid medium also gave IV in 68% yield, whereas in neutral medium, Pd-C selectively reduced the pyridinium group of 2-[(1,2,3,6-tetrahydro-1-pyridyl)methyl]pyridine 1-oxide (VI) to yield 6.3% V and 40% 2-piperidinomethylpyridine 1-oxide (VII); picrate m. 132-3°. VI, picrate m. 115-16°, was prepared in 92% yield by reducing II (X = I) with NaBH4 at room temperature, and VI was deoxygenated by adding PCl3 in CHCl3 under ice cooling and refluxing the mixture 30 min. on a water bath to yield 34% 1-(2-pyridylmethyl)-l,2,3,6-tetrahydropyridine (VIII), b4 106-11° (picrate m. 171-2°), prepared also in 63% yield by warming 2-(BrCH2)C5H4N.HBr 30 min. with Δ3-piperidine-HCl and K2CO3 on a water bath. Similarly, refluxing free 2-(BrCH2)C5H4N with piperidine in EtOH 1 hr., evaporating the solvent, and making the residue alk. with K2CO3 yielded 100% V. VII, m. 93 5°, was prepared in 10% yield by refluxing 2-(BrCH2)C5H4NO 3 hrs. with piperidine in EtOH, and this, as was VI, was deoxygenated with PCl3 in CHCl3 to yield 48% V. VI and VIII sep. catalytically hydrogenated (Raney Ni) yielded, resp., 17% and 95% V. II, reduced by warming 3.5 hrs. at 60° with Zn dust and AcOH, was cleaved to yield 58% 2-picoline (picrate m. 164-5°) and 51% C5H5N (picrate m. 165-7°). In the experiment, the researchers used many compounds, for example, 1-Methyl-1H-benzo[d]imidazole-2-carbaldehyde (cas: 3012-80-4COA of Formula: C9H8N2O).
1-Methyl-1H-benzo[d]imidazole-2-carbaldehyde (cas: 3012-80-4) belongs to imidazole derivatives. Imidazole is the basic core of some natural products such as histidine, purine, histamine and DNA based structures, etc. Among the different heterocyclic compounds, imidazole is better known due to its broad range of chemical and biological properties. Imidazole also acts as a microtubule destabilizing agents and inhibits topoisomerase and Cytochrome P450 Family 26 Subfamily A Member 1 (CYP26A1) enzymes.COA of Formula: C9H8N2O
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem