Amines acid 2-mercapto

The methods outlined, of course, are readily applicable to a wide variety of substituted heterocycles like the carboxyl, hydroxy and mercapto derivatives of pyridines, pyridine 1-oxides, pyrroles, etc. The application to amines and to diaza compounds such as pyrimidine, where the two centers are basic, is obvious except that now 23 takes the role of the neutral compound, 21 and 22 the roles of the tautomeric first conjugate bases, and 20 the role of the second conjugate base. Extensions to molecules with more than two acidic or basic centers, such as aminonicotinic acid, pyrimidinecarboxylic acids, etc., are obvious although they tend to become algebraically cumbersome, involving (for three centers) three measurable Kg s, four Ay s, and fifteen ideal dissociation constants (A ), a total of twenty-two constants of which seven are independent. 

Alkylthio, arylthio, and thioxo. The thioxo group in pyrimidine-2,4-dithione can be displaced by amines, ammonia, and amine acetates, and this amination is specific for the 4-position in pyrimidines and quinazolines. 2-Substitution fails even when a 5-substituent (cf. 134) sterically prevents reaction of a secondary amine at the 4-position. Acid hydrolysis of pyrimidine-2,4-dithione is selective at the 4-position. 2-Amination of 2-thiobarbituric acid and its /S-methyl derivative has been reported. Under more basic conditions, anionization of thioxo compounds decreases the reactivity 2-thiouracil is less reactive toward hot alkali than is the iS-methyl analog. Hydrazine has been reported to replace (95°, 6 hr, 65% 3deld) the 2-thioxo group in 5-hexyl-6-methyl-2-thiouracil. Ortho and para mercapto- or thio- azines are actually in the thione form. ... 

Substituents in the 6-position (cf. 267) show appreciable reactivity. 6-Bromo-as-triazine-3,5(2j, 4j )-dione (316) undergoes 6-substitution with secondary amines or hydrazine, with mercaptide anions or thiourea (78°, 16 hr), with molten ammonium acetate (170°, 24 hr, 53% yield), and with chloride ion during phosphorous oxychloride treatment to form 3,5,6-trichloro-as-triazine. The latter was characterized as the chloro analog of 316 by treatment with methanol (20°, heat evolution) and hydrolysis (neutral or acid) to the dioxo compound. The mercapto substituent in 6-mercapto-as-triazine-3,5(2iI,4if)-dione is displaced by secondary... 

Ring closure to [l,2,4]triazolo[3,4- ][l,3,5]thiadiazines by utilizing the Mannich reaction has been published by a Chinese team <1999SC2027, 2001SC2841, 2001JF1C929> (Scheme 23). 5-Aryl-substituted 3-mercapto[l,2,4]tri-azoles 123 were treated with formaldehyde and primary amines under acidic conditions to yield the fused thiadiazines 124. The reaction was interpreted to proceed via formation of intermediate 125 upon the reaction of 123 with a... 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

Formation of compounds like 115 seems to have occurred in the similar way as it was established for anilines and other primary amines [167]. The initial step of this reaction is treatment of aldehyde with aminozole giving Schiff base 116. Further, nucleophilic attack of imine carbon by mercapto moiety of the acid leads to the intermediate 117 and its subsequent cyclization via gem-diol 118 yields target heterocycles 115 (Scheme 55). 

Reactions at high dilution between the appropriate bis sulfenyl chlorides and primary amines have led in low yields to the 1,3,2-dithiazole derivatives (196) and (197), and nitrosation of substituted 2-mercapto-2-phenylacetic acids in Ac20 gives mesoionic compounds (12) (81LA1025). 

Using the HSAB principle, one can rationalize the corrosion inhibition of iron and aluminum by phosphate in which iron phosphate and aluminum phosphate are produced. Ferric and Al3+ are hard acids, and they react with phosphate, a hard inhibitor and give corrosion protection. Corrosion inhibition of Cu2+ and Zn2+ by amines can be rationalized by the formation of amine complexes of Cu2+ and Zn2+, and this is in accord with the principle that Cu2+ and Zn2+ are borderline acids reacting with amines which belong to borderline inhibitors. Corrosion protection of copper (soft acid) by mercapto-benzothiazole (soft inhibitor) is also in keeping with the HSAB principle. 

Traditional routes to phenoxazines (e.g., 72) include the thermolysis of 2-aminophenol 70 and catechol 71 (Scheme 40) or catechol and ammonia. Phenothiazines are prepared by heating diphenylamines with sulfur as exemplified in Scheme 41 < 1985AXC1062, CHEC-III(8.09.9.2)655>. 2-Hydroxy- (or mercapto-) 2,4-dinitrodiphenylamines 73 cyclize to phenoxazines (or phenothiazines) in the presence of base by elimination of nitrous acid. These reactions are complicated by Smiles-type rearrangements of the amines 73 so that mixtures of isomeric products 74 and 75 are obtained (Scheme 42). 

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