Thiopyridine

This group, which is more stable than the 2-hitrobenzenesulfenamide, has been developed to protect amino acids. It is readily introduced with the sulfenyl chloride (52-74% yield) and is cleaved with triphenylphosphine or 2-thiopyridine N-oxide. It is stable to CF3COOH but can be cleaved with 0.1 M HCl. ... 

Triphenylphosphine, pentachlorophenol, or 2-thiopyridine A-oxide. The group is stable to CF3COOH, but can be cleaved with 0.1 M HCl. ... 

A route to pyridines which involves an isolated 1,5-dicarbonyl compound, has been reported. Aldol reaction of enone 57 with methylketone 58 generated 1,5-diketone 59. When this was submitted to the reaction conditions for a Krohnke reaction, thiopyridine 60 was isolated. 

Among the most useful radical fragmentation reactions from a synthetic point of view are decarboxylations and fragmentations of alkoxyl radicals. The use of (V-hydroxy-2-thiopyridine esters for decarboxylation is quite general. Several procedures and reagents are available for preparation of the esters,353 and the reaction conditions are compatible with many functional groups.354 f-Butyl mercaptan and thiophenol can serve as hydrogen atom donors. 

A more traditional cephalosporin analogue is cephapirin (22). It was made by reacting 7-aminocephalo-sporanic acid with bromoacetyl chloride to give amide 21. The halo group was displaced by 4-thiopyridine... 

The length of the promoter seems to be of little importance with respect to activity. HSPO -, thiopyridine and 1,2 bis(4-pyridyl)ethene (compounds 11, I and 14 in Figure 3.90) all show roughly equivalent activities although they are markedly different in length (2.9 A, 4.6 A and 9.2 A respectively). 

Amino-3-(A,iV-dimethylcarbamoyl)thiopyridine was reacted with EMME or di-(4-methoxybenzyl) (4-methoxybenzyloxy)methylenemalo-nate at 100-120°C for 1 hr to afford 2-pyridylaminomethylenemalonates (50) in 76 and 80% yields, respectively (86EUP218423). 

The electrooxidation of thiophenol [19], 2-mercaptobenzothiazole [22], 6- and 2-thiopurine [23], 2-thiopyridine [24] results in their disulfide derivatives in good yields. Bifunctional compound, 2,6-purinedi-thiol [23] can form first a 6,6 -disulflde (4), and then, by subsequent oxidation of the latter, give a cyclic product with two S - S bridges (Scheme 5). 

Carbohydrate anisyl tellurides are easily prepared by treatment of the corresponding mesylates or tosylates with the anisyl teUurolate anion. By irradiation of these tellurocarbohy-drates in the presence of M-acetoxythiopyridone and the electrophilic olefin, the tandem addnct is formed. The oxidative elimination of the thiopyridine moiety leads to the trans-olefms. ... 

The coordination abilities of A-heterocyclic thiols such as 2-thiopyridine, HSpy (66a), 2-mercapto-pyrimidine, Hspym (66b), or 2-mercaptothiazoline (67) with rhenium centers has already been described for oxorhenium(V) complexes is Section 5.3.2.3.L It has been outlined that ligands with five-membered rings preferably coordinate as monodentate neutral thiones whereas chelate formation is possible for mercaptopyridine or mercaptopyrimidine. Similar complex formation... 

Katritzky et al. reported that alkyl halides convert to thiols in one pot when treated with a thiopyridine, which initially transforms to the pyridi-nium salt (34). Intramolecular ipsosubstitution takes place in the s t (34) by the remote hydroxyl group to afford the corresponding thiols shown in reaction (49) (85TL469). Thus, pyridinium sulfides readily undergo both... 

A range of isothiazolo[5,4-3]pyridines were prepared by cyclization of thiopyridines with iodine/sodium carbonate (Equation 68) <2000FA669>. 

A range of 3//-l,2-dithiolo[3,4-/)]pyridines were prepared by cyclization of thiopyridines with P4S10 in xylene (Equation 71) <2000FAS669>. 3//-l,2-Dithiolo[3,4-/)]pyridines can also be prepared using Lawesson s reagent (Equation 72) <2000FA669>. 

The results clearly showed the importance ordirectionality. 4-thiopyridine is an excellent promoter, while the 2 isomer shows no activity. After adsorption the 4 isomer has the pyridine nitrogen direction out into solution while the 2 isomer points the N back towards the electrode where it is available for adsorption to the gold rather than the cytochrome c. 

Figure 6 RP-HPLC Chromatograms, (a) Retention Behavior of Reduced Peptides A-SH and B-SH, Oxidized Homostranded Molecules A-S-S-A and B-S-S-B, and the Thiopyridine-Derivatized Peptide A (A-S-TP). (b) Products of Air Oxidation, (c) Peptide A-S-TP Titrated with a Molar Equivalent of Peptide B 104la...

The most complete investigation on the thiol/thione tautomerism of thiopyridines and thiodiazines was carried out by Adamowicz and coworkers61 63 123, who presented combined theoretical and experimental IR spectroscopic studies of Ar and N2 matrix-isolated compounds for the whole series. 

These authors also show that irradiation by UV light strongly influences the tautomeric equilibria for oxopyridines as well as for thiopyridines and thiodiazines. More importantly, this provided a reliable method to determine the relative abundance of thiol and thione... 

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