6- pyridine-3-thiol

Reaction of the pyridine-2-thiol (109) with ketones and with triethyl orthoformate has led to A(5-acetals (112) and 1,3,4-thiadiazoles (110) which on methylation and subsequent ring opening gave two new pyridine derivatives (113) and (111) <96JPR516>. 

Carboxylic acid esters of thiols are considerably more reactive as acylating reagents than the esters of alcohols. Particularly reactive are esters of pyridine-2-thiol because there is an additional driving force in the formation of the more stable pyridine-2-thione tautomer. 

Additional acceleration of acylation can be obtained by inclusion of cupric salts, which coordinate at the pyridine nitrogen. This modification is useful for the preparation of highly hindered esters.122 Pyridine-2-thiol esters can be prepared by reaction of the carboxylic acid with 2,2 -dipyridyl disulfide and triphenylphosphine123 or directly from the acid and 2-pyridyl thiochloroformate.124... 

The addition of Grignard reagents to aldehydes, ketones, and esters is the basis for the synthesis of a wide variety of alcohols, and several examples are given in Scheme 7.3. Primary alcohols can be made from formaldehyde (Entry 1) or, with addition of two carbons, from ethylene oxide (Entry 2). Secondary alcohols are obtained from aldehydes (Entries 3 to 6) or formate esters (Entry 7). Tertiary alcohols can be made from esters (Entries 8 and 9) or ketones (Entry 10). Lactones give diols (Entry 11). Aldehydes can be prepared from trialkyl orthoformate esters (Entries 12 and 13). Ketones can be made from nitriles (Entries 14 and 15), pyridine-2-thiol esters (Entry 16), N-methoxy-A-methyl carboxamides (Entries 17 and 18), or anhydrides (Entry 19). Carboxylic acids are available by reaction with C02 (Entries 20 to 22). Amines can be prepared from imines (Entry 23). Two-step procedures that involve formation and dehydration of alcohols provide routes to certain alkenes (Entries 24 and 25). 

Cyclic ylide complexes are readily oxidized not only by aggressive reagents like elemental halogens but also by milder oxidants like disulfides, or even mercaptanes in the presence of molecular oxygen, as shown for a reaction with pyridine-2-thiol in air (Equation (34)).182 A similar reaction is known to take place with thiuramdi-dulfides.2,180... 

Thiols like pyridine-2-thiol yield (carbene)gold thiolates, and onium salts give cationic (carbene)gold ylide complexes, isolated and characterized as the perchlorates.170 The reaction of dithiocatechol with (cyclohexylisocya-nide)gold chloride affords a carbene complex [(CyNC)AuC(NHCy)2]+Cl-, which co-crystallizes with a neutral tetranuclear complex [(CyNCAu)2Au2(S2C6H4)2].224... 

A three-component domino reaction of isobutyral-dehyde, N-benzylidene aniline and pyridine-2-thiol as nucleophile gives access to 1,2,3,4-tetrahydroquino-lines as shown by Annunziata et al..161... 

Similar 1,2,3-diheterocyclizations have been performed by addition of other Af, N- or Al,5-dinucleophiles, such as pyridine-2-thiol, 2-aminopyridine, 2-aminothia-zole, thioisonicotinamide, and l//-benzotriazole, to complexes 6 and 46 giving rise to the formation of the five- and six-membered cyclic alkenyl derivatives 96-100 (Fig. 19) [289, 291,292],... 

Pr Pro ptz pvp py pyca pycaH pyo pyr pys pySH pySSpy iso-propyl = 2-propyl proline phenothiazine polyvinyl pyridine pyridine pyridine-2-carboxylato(l -) pyridine-2-carboxylic acid pyridine iV-oxide pyrimidine pyridine-2-thiolato(l -) pyridine-2-thiol 2,2 -bis(pyridyl) disulfide... 

In human applications, bis(pyridine-2-thiol-l-oxidato)zinc chelate has bacteriocidal and fungicidal properties comparable with selenium sulphide but is less toxic to mammals, making it suitable for controlling dandruff and seborrhoeic dermatitis138. ... 

The crystal structure of the dithioacetylacetone (sacsacH) complex of cobalt(n), Co(sacsac)2, shows it to be monomeric square planar,164 in marked contrast to the acacH analogue. Pyridine 2-thiol (LH), which can exist as the thione tautomer (31) forms Co(LH)2X2 (X = Cl, Br, or I) complexes these contain the ligand bonded through the sulphur, as evidenced by the presence of a v(N—H) vibration in the i.r. spectra.165 Morpholine 4-thiocarbonic acid (32) also appears to be S-bonded in the CoL2X2 complexes (X = Cl, Br, or I), since the v(C=S) frequency is lowered upon co-ordination.166 The electronic spectra of the CoL2C12 complexes (L = thiourea, A-phenylthiourea, and TViV -diphenylthiourea) have been recorded.167... 

In contrast, treatment of [Rh2(MeC02)4] with pyridine-2-thiol, which exists as the tautomer LH (42), does not cause displacement of co-ordinated acetate but produces [Rh2(MeC02)4(LH)2] 168 its i.r. spectrum confirms S-co-ordination. A Raman spectral study has also been reported for rhodium(n) acetate and other dinuclear species, giving information on the Rh—Rh bond strength.169... 

Reaction of [RuCl2(diene)] (diene = nbd, 1,5-cod) with 2( 1 //)-pyridinethione (pyridine-2-thiol), 2(l//)-pyrimidinethione or benzothiazole-2-thiol (2-mercaptobenzothiazole) (HL) in hot DMF in... 

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