2- pyridine 1-hydroxy sulfide

Many of these a-hydroxy sulfides can be cleaved by a reagent composed of lead tetraacetate, pyridine, and acetic acid in a molar ratio of about 2 4 3 per mole of substrate. A tran -diaxial arrangement is required and highly hindered a-hydro"Xy sulfides are not cleaved. 

Table 12. l-[l-(Phenylsulfanyl)cyclopropyl]alkenes by Dehydration of /J-Hydroxy Sulfides with Thionyl Chloride in Pyridine at 0°C ... 

In contrast to the 4-hydroxy isomers, the thermally stable 5-hydroxy-THISs add to the C=C bond of cyclopropenylidenes (4. 18, 27. 28). The adducts eliminate carbonyl sulfide, and the strained bond breaks resulting in ring-expansion with formation of pyridin-4-ones. -thiones, or -imines. or 4-alkylidenedihydropvridines (20, X = 0. S.NR. or CRR ) (Scheme 19). 

Replacement of a hydroxy with a thiol group, using phosphorus penta-sulfide in refluxing pyridine, has been reported for pyrazolo[4,3-c]pyrid-4-(54-75%)144,146 and pyrazolo[3,4-c]pyrid-7-ones (67%). 10... 

Chloro-l-methylpyridinium iodide (683) functions as an important mediator in a variety of different reactions. Esters are formed in high yield from acids and alcohols when reacted with one equivalent of (683) in the presence of two equivalents of triethylamine (Scheme 158) (75CL1045). cv-Hydroxy acids are lactonized under similar conditions (76CL49). The pyridinium salt (683) will also convert thioureas into carbodiimides (77CL575) and pyridine-2-thiones to pyridyl sulfides (75CL1159). 

REDUCTION, REAGENTS Bis(N-methylpi-perazinyl)aluminum hydride. Borane-Di-methyl sulfide. Borane-Tetrahydrofurane. Borane-Pyridine. n-Butyllithium-Diisobu-tylaluminum hydride. Calcium-Amines. Diisobutylaluminum hydride. 8-Hydroxy-quinolinedihydroboronite. Lithium aluminum hydride. Lithium 9-boratabicy-clo[3.3.1]nonane. Lithium n-butyldiisopro-pylaluminum hydride. Lithium tri-j c-butylborohydride. Lithium triethylborohy-dride. Monochloroalane. Nickel boride. 2-Phenylbenzothiazoline. Potassium 9-(2,3-dimethyl-2-butoxy)-9-boratabicy-clo[3.3.1]nonane. Raney nickel. Sodium bis(2-methoxyethoxy)aluminum hydride. Sodium borohydride. Sodium borohy-dride-Nickel chloride. Sodium borohy-dride-Praeseodymium chloride. So-dium(dimethylamino)borohydride. Sodium hydrogen telluride. Thexyl chloroborane-Dimethyl sulfide. Tri-n-butylphosphine-Diphenyl disulfide. Tri-n-butyltin hydride. Zinc-l,2-Dibromoethane. Zinc borohydride. 

Hydroxy-[l,2,4]triazolo[4,3-fl]pyridine (91) was reluctant to react with the common hydroxylic chlorinating agents, giving at best, the 3-chloro compound in only 15% yield with pWphorus oxychloride-dimethylaniline. Methylation of (91) produced 2-methyl-[l,2,4]triazolo[4,3-n]pyrid-3-one (92) whereas methylation of the 3-thiol (93) resulted in methyl [l,2,4]triazolo[4,3-a]pyrid-3-yl sulfide (94), a molecule also resistant to nucleophilic substitution (66JOC265). Potassium ferricyanide oxidation of (93) resulted in the corresponding disulfide. 

FITS reagents reacted very easily with thiols in the presence of pyridine to give the perfluoroalkyl sulfides in good to high yields. S-perfluoroalkylation was selective in the case of polyfiinctional substrates. In the presence of groups such as hydroxy, carboxy, alkoxycarbonyl or dialkylamino, the sulfur atom was always selectively substituted.216 (Table 5.10)... 

Pyridinols and pyridones and phosphorus pentasulfide give predictable products. 4-Pyridinol and phosphorus pentasulfide in pyridine give 4-pyridine-thione, while 2,6-di-f-butyl-4-pyridone gives bis(4-(2,6-di-r-butylpyridinyl)] sulfide. . /V-Alkyl-3,5-dibromo-2,6-dimethyl- and iV-alkyl-3 -dibromo-2,6-di-phenyl-4-pyridone are converted to the corresponding 4-pyridinethiones. Ammonium salts of 4-alkyI-3,5-dicyano-6-hydroxy-2-pyridones and phosphorus pentasulfide in xylene and pyridine form pyridinium salts of the corresponding 6-mercapto-2-pyridinethiones(XII-630). ... 

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