Pyridine, 2-methylthio

Thiazolo[5,4-6]pyridine, 2-methylthio- H NMR, 6, 674 (76JHC491) Thiazolo[3,2-a]pyridinium... 

Imidazo[l,2-n]pyridine, 5-methyl-2-methylthio-3-substituted synthesis, 5, 632... 

To a solution of methyl 3-oxobutanoate 127 (580 mg, 5 mmol) and l-methyl-2-methylthio-l//-imidazole-5-carboxaldehye 128 (390 mg, 2.5 mmol) in 5 mL of absolute methanol was added a solution of ammonium hydroxide (25%, 0.4 mL). The reaction was heated at reflux overnight before cooling to room temperature and removing the solvent. The crude product was purified by preparative TLC to afford 526 mg of dimethyl l,4-dihydro-2,6-dimethyl-4-(l-methyl-2-methylthio-5-imidazolyl)-3,5-pyridine-dicarboxylate 129 (60%) as a solid, mp = 200-201 °C (MeOH). 

The 3-amino-8-oxo derivative of 1,2,4,5,7-pentaazanaphthalene (475) is known as well as various 3-substituted derivatives of the 6,8-dioxo compound. The 3-methylthio- and 3-ethylthio-6,8-dioxo derivatives and their 7-methyl and 5,7-dimethyl analogs were prepared by ring-closure. 3-Ethylthiopyrimido[4,5-e]-as-triazine-6,8-dione was 3-substituted with alkali 2N, 100°, > 30 min) or acid 2N, 100°, < 2 hr, 70% yield) and with ammonia, aniline, piperidine, or monoalkylamines (in pyridine, 115°, 4 hr, 75-85% yield). ... 

Wlieii thiomethoxymethyl hexachloroaiitimoiiate was treated with pyridine, a methylthio derivative 28 was isolated in low yield in addition to the expected chlorinated sulfides (71T4209). Several A, A -haloalkyl-bis-4,4 -pyridiniumethenes 29 have been reported in a Japanese patent (80JAP75479). Tliese compounds are promising candidates for the construction of electrochromic display devices (Scheme 7). 

Thus, heating under reflux a mixture of 10 and 12 in pyridine afforded, in each case, one product whose H NMR spectrum showed the absence of the methylthio (6 2.55-2.65) and amino (6 5.0-5.03) proton signals present in the spectra of the respective 4-amino-3-methylthio-l,2,4-triazinones 12. Instead, the spectra of the products isolated revealed in each case a characteristic one proton singlet (N-H) in the region S 9.0-9.4. These findings indicate that route A seems to be the most plausible mechanism for the studied reactions of 10 with either 8 or 12 <2000JPR342>. 

Electrophilic cyclization of the precursors 8, which are available from 3-(methylthio)pyridine by regioselective lithiation, followed by introduction of CBr4, and a subsequent Sonogashira coupling, has resulted in a series of thieno[3,2-b]pyridines 9... 

Thiation of [l,2,4]triazino[3,2-h]quinazoline-3,10-dione 782 with phosphorus pentasulfide in pyridine proceeded selectively to give the 3-thioxo analogue 783. The latter was converted to the corresponding 3-methylthio derivative 784 by reaction with methyl iodide. Treatment of 784 with hydrazine gave 785, which was converted to 786 and 787 by cyclization with formic acid or carbon disulfide (90JHC591). Cyclization of 785 with sodium nitrite in hydrochloric acid gave 788 (90JHC591). 

Several Sonogashira adducts of heteroaromatics including some pyridines (see Section 4.3) and pyrimidines underwent an unexpected isomerization [69]. This observed isomerization appeared to be idiosyncratic, and substrate-dependent. The normal Sonogashira adduct 100 was obtained when 2-methylthio-5-iodo-6-methylpyrimidine (99) was reacted with but-3-yn-ol, whereas chalcone 101, derived from isomerization of the normal Sonogashira adduct, was the major product when the reaction was carried out with l-phenylprop-2-yn-l-ol. 

Heating to reflux a pyridine solution of 3-substituted-5-(l-aroyl-l-bromo)methylthio-4-phenylamino-4//-[l,2,4]tria-zoles 81 (available from the corresponding 1,2,4-triazoles with phenacyl bromides and subsequent ultraviolet (UV) light-induced bromination) affords 3-substituted-6-aroyl-5,6-dihydro-5-phenyl[l,2,4]triazolo[3,4-6][l,3,4]thiadiazoles 82 (Equation 19) <1993IJH135>. 

The reactions of 5-methylthio-3-amino- or 3,5-diamino-l,2,4-triazole and diethyl 1-ethoxyethylidenemalonate in boiling ethanol in the presence of sodium ethylate for 1.5-3.5 hr gave l,2,4-triazolo[l,5-a]pyrimidin-7-ones (1123, R = MeS, NH2, R1 = Me) in 44% and 20% yields, respectively. The reaction of 5-methylthio-3-amino-l, 2,4-triazole (R = MeS) and 2-ethoxyethylidenemalonate in boiling pyridine for 4 hr gave 1,2,4-tria-zolo[l,5-a]pyrimidin-5-one (1122, R = MeS, R1 = Me) in 12% yield (61JCS3046). 

The electron impact induced ortho effects in 2-nitro-substituted aromatic sulphides containing e.g. 2-pyridyl, 2-(5-methylthio-l,3,4-thiadiazolyl) moieties have been studied105, the 2,6-bis(nitrophenylthio)pyridines being typical representatives for the compounds studied105. 

The nucleophilic properties of the media are crucial for the nature of the methylthio products formed. With pyridine, a product of vicinal methylthiation-pyridination was obtained. In pure acetonitrile the solvent itself plays the role of a nucleophile [127], whereas in a low-nucleophilic liquid SO2 a product of... 

Under Pummerer rearrangement conditions, a-methylthio amide 248 affords a mixture of 2-piperidone 249 and pyridin-2-(3//)-one 250 (86CPB1061). 

Reaction of methyl 4-amino-l-benzyl-l,2,5>6-tetrahydropyridine-3-carboxylate 601 with ethyl isothiocyanoacetate in refluxing pyridine or ethyl iV-[bis(methylthio)methylene]glycinate (BMMA reagent) in AcOH at reflux temperature gave the pyrido[4,3-r7 pyrimidines 603 and 604, respectively, via intermediate 602 (Equation 50) <2001H(55)115>. 

Nitro-phenyl)-2-piperidino-l,3,4-oxadiazol248 9,1 g (50 mmol) 4-Nitro-benzhydrazid, 80 ml trockenes Pyridin und 12,0 g (56 mmol) (Chlor-methylthio-methylen)-piperidinium-chlorid erhit/t man 2 h auf 70°. AnschlieBend verdiinnt man mit 4%iger Natronlauge, filtricrt und kristallisiert aus Ethanol um Ausbeute 7,3 g (54%) Schmp. 176°. 

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