1-oxide thioalkylation

Pyridinium salts, l-ethoxy-4-methyl-thioalkylation, 2, 230 Pyridinium salts, N-ethyl- H NMR, 3, 893 Pyridinium salts, 2-halo-nucleophilic reactions, 2, 360 N-oxides... 

Oxidative cyclization of dithiobiuret under basic conditions provides bis(5-amino-l,2,4-thiadiazolyl)-3,3 -disulfide 92 via oxidative dimerization of the intermediate 5-amino-3-mercapto-l,2,4-thiadiazole 91. However, alkylation of disulfide 91 under basic conditions gives the thioalkyl-l,2,4-thiadiazole 93 (Scheme 9) <2003H(60)1401>. 

Pyridine 1-oxide and a series of its methyl analogues undergo thioalkylation at the a-and y-positions when heated with an alkanethiol in acetic anhydride at 95 °C for 3 h (Table 13). Under these conditions, attack by thiol at 2- or 4-methyl groups does not seriously compete with ring substitution. j8 -Substitution does not occur at C-3 in 2-methylpyridine, but it does so at C-5 where the adjacent a-position is vacant. Notice that again a 3-methyl substituent tends to direct substitution to C-2 rather than C-6. This is also true for 3,4-dimethylpyridine. Increasing the size of the 4-substituent does reduce the relative... 

Pyridine 1-oxide and methyl analogues undergo thioalkylation at the a- and y-positions with alkanethiols in acetic anhydride (Scheme 19). Some (3-substitution occurs under these conditions probably via episulfonium intermediates, evidence for which comes from the isolation of tetrahydropyridines, e.g. (267). 

Pyridine A-oxide and methyl analogues undergo thioalkylation at the - and -positions with alkanethiols in acetic anhydride (Scheme 30). 

The electrochemical behaviour of the ribbed-functionalized iron(II) [65, 68] and ruthenium(II) [78] clathrochelates with alkylamine, thioaryl, thioalkyl, phenoxyl and crown ether substituents in a-dioximate fragments was characterized by E1/2 values for Fe3+/2+ and Ru3+/2+ couples (Table 37). The Tomes criterion values of most complexes exhibited reversible or quasi-reversible anodic processes. Moreover, the quasi-reversible oxidation processes are accompanied by the formation of insoluble products followed by passivation of the working electrode. The Ev2 values depend on the electron-donating properties of the substituents in the ribbed fragments. The correlations of E1/2 values for Ru3" 2+ and Fe + 2+ couples with these substituents Hammet s Opara constants were observed in Refs. 65, 68, and 78. These correlations are rather qualitative, but they enable one to conclude that ruthenium complexes are less sensitive to the change of substituents in dioximate fragments. There was no correlation between the Em values and the inductive Taft s (cr,) constants for substituents in dioximate fragments. 

The nucleophilic substitution reactions of reactive chlorine atoms in hexachloride cobalt precursors in the presence or absence of an oxidizing agent can be employed to obtain the thioalkyl, thioaryl,... 

Strained -oxidoalkyl i enyl selenoxides, such as l-oxido-l-(r-phenylsdenoxyalkyl)cyclopropanes, derived from oxaspiropentanes with tetraalkyl-substituted oxirane rings, and l-(r-hydroxyalkyl)-l-selenoxycyclobutanes, - obtained on oxidation of the corresponding selenides or on reaction of a-li-thioalkyl selenoxides with cyclobutenones, possess a high propensity to rearrange to cyclobutanones... 

Acid hydrolysis will often convert thione, thioalkyl, and imino derivatives into the oxy analogues, and sulfur functions can also be directly oxidized to oxo <85PS(22)49, 91TL4791>. When mercuric acetate was used to convert the l,3-diacylimidazolidin-2-thione (138) into the corresponding imi-dazolidinone (139) the process was believed to proceed as in Scheme 70. 

Oxidation of allylic and homoaUyic alcohols. A convenient route to 3-thioalkyl-2-cycloalkenones is based on the established pattern of transpositional oxidation of tertiary allylic alcohols. The substrates are readily prepared by reaction of the enones with phenylthiomethyllithium or l,3-dithian-2-yllithium reagents. 

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